Inflammation is activation of the immune system in response to threat or injury to the body. Acute inflammation mobilizes the immune system to repair an injury or fight an infection. Once healing takes place the immune system goes back to baseline. Chronic inflammation, however, involves long term activation of the immune system caused by some ongoing stress to the body. More and more, researchers are beginning to show that chronic inflammation is the common pathway to many diseases. There are multiple causes of chronic inflammation. In this post I will write about the causes of chronic inflammation. I will also do a series of posts about the many diseases that chronic inflammation causes. These posts will be based on the structure of an excellent book: Inflamed – Deep Medicine and the Anatomy of Injustice. It is not easy to read because it is disturbing but I highly recommend it. I will also write about a test to measure chronic inflammation. I will write about things you can do to decrease chronic inflammation if you have it and how to prevent it if you don’t. There are many causes of chronic inflammation that have to do with the structure of our society. These are things an individual cannot control. These societal causes will take ongoing efforts by all of us to change some of the toxic structures of society.
The Process of Inflammation
The inflammatory process starts with damage or threat of damage to the body. That can be an infection, a wound, or perceived threat of such. The immune system mobilizes white blood cells called macrophages to the injured area or site of infection. The cells of the immune system also release a cascade of messenger molecules called cytokines that amplify inflammation. These include interleukin 1ß, interleukin- 6 and tumor necrosis factor -α. The liver also releases a protein called c-reactive protein. When the threat is neutralized the immune system helps the body start to heal by releasing anti-inflammatory cytokines including interleukin (IL)-1 receptor antagonist, IL-4, IL-10, IL-11, and IL-13.
In chronic inflammation the pro-inflammatory cytokines continue to predominate and the c-reactive protein continues to be elevated.
Causes of Chronic Inflammation
Causes an individual can do something about
Low levels of physical activity.
Having a BMI at or above 30 , especially when excess weight is deep within your belly (visceral fat). The best way to measure belly fat is to use a tape measure to measure your waist at the widest point. Increased belly fat is greater than 35 inches for women or greater than 40 inches for men
An imbalance of healthy and unhealthy bacteria in your intestine (dysbiosis). Dysbiosis can be caused by antibiotics and by eating foods low in soluble fiber.
Regularly eating foods that cause inflammation, especially highly processed foods, or foods high in sugar or salt
Inadequate sleep
Using tobacco products.
Regularly drinking too much alcohol
Periodontal disease (gum infection) and tooth decay
Perceived stress
Societal Causes
Experience of racism (structural or personal)
Poverty
Homelessness
Worry about debt
Work stress
Exposure to air pollution
Exposure to chemicals (pesticides and herbicides for farm workers, glyphosphate (RoundUp) for everyone, microplastics in our bloodstreams for everyone. Every day, we are surrounded by thousands of synthetic chemicals. They are in our food, clothes, tools, furniture, toys, cosmetics and medicines. We know the health effects of only a few of these).
All of the inflammatory cytokines can be measured but those are expensive tests. A simple inexpensive test that measures inflammation, both acute and chronic is high sensitivity CRP. It will also be high with an acute infection or injury, but will return to normal after the infection or injury have resolved. If it remains elevated when you are not sick or injured it is a sign of chronic inflammation. It may be worth asking your doctor to order this test if you have any of the individual or societal risk factors for chronic inflammation. A normal hs-CRP is less than 0.55 mg/dl in men and less than 1.0 mg/dl in women. If your hs-CRP is high in the absence of acute infection or injury, that can serve as motivation to make lifestyle changes to decrease your chronic inflammation and put you in a population that has less risk of developing any of the diseases associated with chronic inflammation.
Anti-inflammatory lifestyle
Exercise regularly. The CDC recommends 30 minutes of moderate exercise (walking briskly) for 30 minutes at least 5 days a week.
Eat mostly unprocessed or minimally processed foods and avoid sugary drinks or foods with added sugar or high fructose corn syrup. Also include foods with high soluble fiber such as beans, carrots, sweet potatoes, nuts, berries and most fruits (not fruit juice). Organic foods, while more expensive, have no residual pesticides or herbicides. If you eat meat buy grass fed beef, and pasture raised chicken and pork. Eat more plant-based foods than meat.
Avoid taking antibiotics as much as possible
Sleep. Average at least 8 hours a night
Floss your teeth daily, brush twice a day and see your dentist every 6 months
If you don’t smoke, don’t start and if you do smoke quit.
It is better not to drink alcohol at all, but if you do limit it to 1 drink a day or less.
Learn meditation or self hypnosis to manage stress. There are good books and videos, but an in person course is best if it is available.
Drink only filtered water and not bottled water in plastic bottles
Gas stoves cause significant indoor air pollution. If possible switch to an electric stove. Induction type burners actually heat more quickly than gas. If you have to use a gas stove, be sure to turn the ventilator fan on and open a window if possible.
Bottom Line
Chronic inflammation is the common pathway for many chronic diseases. There are many individual strategies that reduce or prevent chronic inflammation. Many of these strategies are not possible for people with socioeconomic problems. The stress black people experience from structural and individual racism, homelessness or inadequate housing, anxiety over debt, exposure to environmental synthetic chemicals, and exposure to air pollution are societal problems that we all have a responsibility to address.
My next post will deal with chronic inflammation and cardiovascular disease.
Humans have been drinking beverages containing alcohol for well over a thousand years. Mild to moderate acute alcohol intake has a euphoric effect probably caused by release of dopamine in the brain. At lower blood levels alcohol promotes social interaction, which is likely why it has such a long history of use in human society. The actual effect of alcohol on the brain is complex and not well understood. Brain function is a delicate balance of excitatory and inhibitory neurotransmitters. Alcohol alters this balance in a complex way that is difficult to measure and characterize.
Addiction to alcohol occurs in some people. About half of alcohol addiction is genetically determined. Other causes include use to alleviate mental disorders such as anxiety or depression or psychosocial stress. Physicians used to use the term alcoholism to refer to alcohol addiction, but now the correct term is alcohol use disorder. This can range from mild to severe and is defined by NIH as a medical condition characterized by an impaired ability to stop or control alcohol use despite adverse social, occupational, or health consequences. Severe alcohol use disorder has major health and social consequences for both individuals and society.
In this post I’m not going to write further about alcohol use disorder. That is a subject unto itself. Instead I’m going to focus this post on the health effects of alcohol use that does not meet the definition of alcohol use disorder, so called “social drinking.”
Physicians used to say that a safe level of alcohol use was 2 drinks a day for a male and 1 drink a day for a female. Now physician advice is that no level of alcohol use is safe. Alcohol use has been shown to increase the risk of many cancers as well as heart disease. The real question is how big is the risk for these conditions and at what level of alcohol intake.
Measuring alcohol use
The term “drink” is not very precise. I once had a patient who insisted she only had one drink a day. Her one drink consisted of a 12 ounce glass of vodka. The UK has developed a different measure of alcohol intake called units of alcohol. One unit of alcohol is the amount an average person can metabolize completely in 1 hour. That amount is 10 cc (1/3 of an ounce) or 8 grams of pure alcohol. Here is a list of the number of units in beer, wine and cocktails:
Four ounce glass of wine (red or white) – 1.5 units
Six ounce glass of wine (red or white) – 2.1 units
Eight ounce glass of wine (red or white) – 3 units
Low alcohol pint of beer – 2 units
High alcohol pint of beer – 3 units
Bottle of beer – 1.7 units
Cocktails – 2.5-3 units
If you drink alcohol, add up the number of units you drink per week. The greater the number of units per week, the higher the risk, which I will quantify below. Be aware that most of these risks are very small. There are quite a few people who don’t drink at all or drink only rarely. These people simply don’t have any desire to drink alcohol or don’t like the way it makes them feel. These essentially non-drinkers form the comparison group for the risk of drinking alcoholic beverages.
Risk of Alcohol Use Disorder
The vast majority of social drinkers do not develop alcohol use disorder, but people who have a family history of alcohol use disorder are at greater risk if they start social drinking. Social drinking is also not a good idea for people with severe anxiety or depression.
Risk of Cancer
Drinking alcohol increases the risk of certain cancers, particularly colorectal cancer, breast cancer, liver cancer, esophageal cancer, and throat cancer. The total absolute cancer risk for drinking greater than 14 units of alcohol per week from age 25 to 85 is 4% for men and 5.4% for women. That translates to an annual risk of .0667% for men and .09% for women. To put that risk in perspective, the annual risk of death from a car accident in the US is .013%. and the annual injury risk from a car accident is 1%.
Risk of Death
In a large study in the UK, risk of death from all causes was associated only with drinking more than 42 units of alcohol per week.
Accelerated Ageing
Recent studies have looked at two measures of biologic ageing. At the end of each chromosome are structures called telomeres. It is known that these telomeres shorten as a person ages. The other measure is called epigenetics. These are non-DNA changes that are heritable. Some of these epigenetic changes increase as a person ages. Recent studies show an association between alcohol intake and these biologic ageing changes. There seems to be a dose response relationship. The more alcohol you drink, particularly liquor as opposed to beer and wine, the more your telomeres shorten and epigenetic changes accumulate. This association was most marked in people with alcohol use disorder. There was little association for light to moderate social drinkers. Association does not mean causation, however the researchers controlled for other things that might account for these changes like smoking, diabetes, and others. It is possible and even likely that these ageing changes were caused by alcohol intake.
Risk of Accidents
Even mild to moderate drinking impairs reaction time so driving after drinking any amount of alcohol is not a good idea. Heavier drinking causes more impairment of motor function and increases risk of accidents such as falls. Driving after heavier drinking markedly increases the risk of auto accidents, which can injure or kill others as well as the one who is drinking. Anyone who drinks any amount of alcohol outside the home should have a designated driver who agrees not to drink, or call Uber, Lift, or a taxi to be driven home.
Sleep Disturbance
Drinking alcohol, particularly later in the evening can cause sleep disturbance with early awakening and difficult getting back to sleep. This can occur even with light to moderate drinking.
Bottom Line
Drinking alcohol at all does increase the risk of cancer and heart disease. The annual risk is dose related, but is still very small for light and moderate drinkers (14-21 units per week) The risk of illness and death and accelerated ageing is higher for heavier drinkers, but still relatively small. Drinking alcohol later in the evening often causes sleep disturbance. This can usually be avoided by timing drinking alcohol in the late afternoon or early evening. The risk of cancer and heart disease from drinking is low but not zero. People who choose to drink alcohol are accepting that risk. Driving is not a good idea for any level of alcohol intake. Light to moderate drinking is definitely less risky than heavier drinking, which includes association with accelerated ageing as well as increased risk of auto accidents. These risks are still fairly small. People who have alcohol use disorder should seek professional help and strive to be completely abstinent from alcohol.
The benefit of cancer screening tests like pap smears, colonoscopy, mammography and others are reported in two ways. The most common way is the relative risk reduction. This is a ratio of the risk in the screened group divided by the risk in the non-screened group. Relative risk does not take into account the baseline risk in the whole population. The other way of reporting benefit of a screening test is called absolute risk reduction. Absolute risk reduction is the risk in the non screened group minus the risk in the screened group. Relative risk reduction always looks a lot bigger than absolute risk reduction because it does not take into account the baseline risk. Absolute risk reduction is what you really want to know. Absolute risk reduction lets you know how much your risk is reduced by taking the screening test. It is always a lot lower than the relative risk reduction. Absolute risk reduction of the most common cancer screening tests is very low, usually 1% or less.
Here are some examples:
Mammography: Relative breast cancer death risk reduction 30%; Absolute cancer death risk reduction 1%
Colonoscopy: Relative colon cancer death risk reduction 50%; Absolute death risk reduction 0.15%
Pap Smear: Relative cervical cancer death risk reduction 80%; Absolute cervical cancer risk reduction .08%
Another number that can be helpful is called Number Needed to Screen (NNS). NNS is the number of people who need to be screened to prevent 1 death from the disease. NNS is just 1 divided by the absolute death risk reduction for the screening test. Here are the NNS’s for the examples above.
Mammography: NNS 1/.01= 100 (this is mammograms every 2 years from age 50-75 so the the 100 patients means about 1100 mammograms).
Colonoscopy: NNS 1/.15=667
Pap Smear: NNS 1/.08=1,440
PSA: NNS 1/.09 =1,111
Sensitivity and Specificity
Any test, including cancer screening tests have a certain sensitivity and specificity.
Sensitivity
The sensitivity of a test is the probability that the test will detect the disease if it is present. In other words it measures how likely it is to get a falsenegative test. The higher the sensitivity, the less likely the test will be negative if the person has the disease being tested for. It is expressed as a percentage.
Specificity
The specificity of a test is the probability that a person with a positive test will have the disease. In other words it measures how likely it is to get a falsepositive test. The higher the specificity, the more likely a person with a positive test will have the disease. It is also expressed as a percentage
An ideal test has both a high sensitivity and specificity. Lets look at the sensitivity and specificity of our cancer screening tests.
Mammography: sensitivity 72%; specificity 98%
Colonoscopy: sensitivity 85%; specificity 90%
Pap Smear with HPV testing: sensitivity 95%; specificity 97%
PSA: Sensitivity 30%; Specificity 91%
Bayes Formula
All of these cancer screening tests have high specificity but somewhat less sensitivity except for Pap smears with HPV testing, which have high sensitivity and high specificity. So why are the absolute death reductions so low? Part of it has to do with something called Bayes Formula. It turns out that the chance of a false positive has to do not just with the specificity, but also the frequency of the disease in the population being screened. If the frequency of the disease in the population being screened is low, then even with a test that has high specificity, the chance of a positive test being a false positive is higher than than the specificity would suggest. The frequency of all of the above cancers is low in any 1 year in the population so that means that false positive cancer screening screening tests are common. Below are population frequencies for each cancer per year.
Breast cancer: annual prevalence in women 0.13%. Chance of a positive mammogram being a true positive: 28%. This means that a positive mammogram has 72% chance of being a false positive. On the other hand, a negative mammogram has an 8.7% chance of being a false negative, that is of missing a breast cancer
Colorectal cancer: annual prevalence in population .03%. Chance of a positive colonoscopy being a true positive: 2.5%. That means that a colonoscopy that finds something only has a 2.5% chance of being cancer. On the other hand, a negative colonoscopy has only a .005% chance of being a false negative. That means a negative colonoscopy has only a tiny chance of missing a cancer.
Cervical Cancer: annual prevalence in population 0.0077%. Chance of a positive pap smear being cancer: 0.24%. That means that 99.86% of positive pap smears with HPV testing will not be cervical cancer. On the other hand the chance that a negative pap smear with HPV testing will be a false negative is .00041%. Obviously a negative pap smear with HPV has an infinitesimally small chance of missing a cervical cancer. Although the chance of finding a cervical cancer is very low, the pap smear with HPV also finds precancerous changes in the cervix. Treatment of these precancerous cells prevents cervical cancer from developing. That is a big reason why the prevalence of cervical cancer is so low.
Prostate Cancer: annual prevalence in men .66%. Chance of a positive PSA (>4) being a true positive 2.18%. That means a PSA of >4.0 has a 98% chance that no prostate cancer is present. On the other hand a PSA of <4.0 has a 5.1% chance of missing a prostate cancer.
The somewhat lower sensitivity of mammography, colonoscopy and especially PSA means that false negatives are fairly common, for these tests.
The combination of false positives, false negatives and low prevalence of these cancers in the population all contribute to the small absolute death risk reduction for all four of these cancer screening tests. For patients at substantially higher risk, such as strong family history of breast or colon cancer, the screening tests perform much better, because the high risk population has a much greater disease prevalence than the general population.
Over Diagnosis
Another problem with cancer screening tests is over diagnosis. Over diagnosis means that a positive test finds a cancer, but the cancer grows so slowly or spontaneously disappears so that it never would have caused any symptoms in the person. Over diagnosis then leads to unnecessary treatment. So let’s look at the over diagnosis rate for our four cancer screening tests.
Mammography: Over diagnosis rate for women 40 and over is 12%. This means the 12% of women diagnosed with breast cancer by mammography will be treated for cancer unnecessarily.
Colonoscopy: The over diagnosis problem with colonoscopy results from the removal of polyps. All visible polyps are removed during colonoscopy. The polyps that have some chance of turning into cancer are called adenomatous polyps. Only 8% of these turn into invasive colon cancer over 10 years. That suggests that 92% of the adenomatous polyps removed at colonoscopy would never turn into cancer. Removal of all adenomatous polyps does prevent some colon cancers. It is not possible to know at the time of removal which polyps are going to progress. The cost of prevention of some colorectal cancers is substantial over diagnosis.
Pap Smear with HPV: Overdiagnosis of precancerous cervical lesions is high. We now know that cervical cancer is caused almost exclusively by the HPV virus. On the other hand, women often clear an HPV infection on their own without treatment. This is particularly the case with young women, which is why pap smears and HPV testing are not recommended before age 21. Precancerous cervical lesions are graded CIN1-CIN3, CIN3 being the most severe. Overdiagnosis rates are higher for the lower grade lesions, which most often clear on their own. The figures for over diagnosis over women’s lifetime were 70.6% for CIN1+, 63.2% for CIN2+, and 50.0% CIN3+.
PSA test for prostate cancer: Low grade prostate cancer is common as men age. Many of these cancers would never cause symptoms during the lifetime of the men. Current estimates are that 60% of prostate cancers detected by PSA would never cause symptoms or death from prostate cancer. Treatment of prostate cancer often results in permanent urinary incontinence and/or sexual dysfunction. This very large over diagnosis and therefore unnecessary treatment is why PSA testing is so controversial. There are certain populations of men who are at high risk of aggresive prostate cancer and these men are probably the only ones who should have routine PSA testing. Here is a link to a risk calculator for prostate cancer: PCPT Risk Calculator.
Bottom Line
Despite the high specificity of cancer screening tests, Bayes Formula shows that false positive tests will be more frequent than true positive tests. For mammograms, colonoscopy and PSA the somewhat low sensitivity means that there will be some false negative tests. In other words, they will miss a few cancers. Pap smear with HPV has the lowest chance of missing a cancer. Over diagnosis is a problem with all cancer screening tests, resulting in unnecessary treatment. This is particularly a problem for breast cancer and especially prostate cancer. The low absolute death risk reduction values and the over diagnosis problems for these tests do not mean you should not be screened, especially if you are in a higher risk population due to family history or other causes of higher cancer risk. All of these screening tests save lives, just not as many as the relative risk values suggest. The vast majority of people will not benefit from these tests and some will be harmed by unnecessary treatment, but a small but substantial number will have their lives saved.
People who are faced with a new diagnosis of cancer frequently turn to the internet to learn about treatment. Although there is good and reliable information about cancer and cancer treatment on the internet, it is much more common for people to find websites promoting various natural and alternative treatments for cancer as opposed to medically proven treatments such as surgery, radiation, chemotherapy and immunotherapy. Is there evidence that any of these alternative treatments work as well as or better than traditional cancer treatment?
This post will explore the most commonly recommended natural and alternative cancer treatments and present the evidence, if any, that any of them work.
CBD and THC
There is some evidence in tissue culture studies that cannabinoids like CBD and THC inhibit cancer cells. There have been some limited clinical trials in humans using cannabinoids as treatment. None of these trials has shown any beneficial effect on any cancers in humans.
Chinese Herbal Medicines
Traditional Chinese medicine uses a completely different framework than western medicine for health and disease. It has been used and developed for thousands of years. It focuses on restoring natural balance of the opposing forces of yin and yang. Treatment is individualized based on the imbalance diagnosed by the practitioner. In China, traditional Chinese medicine is frequently used as an adjunct to cancer treatment with surgery, chemotherapy and immunotherapy. Combinations of herbs are used as well as things like acupuncture and qigong. There is some evidence that the some of the herbs used in traditional Chinese medicine have some anticancer properties, but because of the individual nature of treatment it is almost impossible to do randomized trials. There is no good evidence that traditional Chinese herbal medicines alone successfully treat any cancers. There is evidence that people in China who use traditional Chinese medicine as an adjunct to other cancer treatments have fewer side effects from anticancer drugs and have better quality of life during treatment.
Ayurvedic Medicine
Another old (5000 year old) system from India that also teaches that disease is due to imbalance that can be corrected with traditional Indian herbal medicines. There are no clinical trials that show the Ayurvedic medicine cures or treats any cancers.
Special Diets
Many types of diets have been proposed to treat cancer. There is no evidence that any dietary changes treat any cancer. Plant based diets have been shown to decrease the risk of getting certain cancers, but there is no evidence plant based diets successfully treat any cancer.
Other unproven and disproven cancer treatments
There are numerous other alternative or natural cancer treatments that have been proposed by many different groups. They are in fact too numerous to mention separately in this post. There is an excellent Wikipedia article that has a comprehensive list of unproven and disproven cancer treatments. Here is a link to that web page: List of unproven and disproven cancer treatments.
Bottom Line
People who use natural and alternative cancer treatments tend to substitute those for proven medical treatments like surgery, chemotherapy and immunotherapy. As a result, people who use these therapies as an alternative to proven treatments have quicker progressions of cancer and die sooner than people who use proven therapies. Some alternative therapies used as an adjunct to proven therapies may improve quality of life during treatment. Because some herbal medicines can interact with chemotherapy drugs, it is important that your cancer treatment doctor knows that you are using one of these alternative therapies as an adjunct to the treatment he/she is giving you for your cancer.
Most people know these new effective weight loss drugs by their trade names: Ozempic, Wegovy and Mounjaro. Ozempic and Wegovy are different names for semaglutide. Mounjaro is the trade name for tirzepatide. All of these drugs are in the same class. They are called GL-P1 agonists. They mimic the action of a hormone called glucagon-like peptide. These drugs were developed to treat type 2 diabetes. They lower blood sugar by causing insulin release and also by delaying stomach emptying, which delivers less glucose to the bloodstream. The slowing of emptying from the stomach decreases appetite and causes an increased feeling of fullness. People on these drugs tend to reduce their calorie intake fairly markedly and that is how they work for weight loss.
Common Side Effects
The most common side effects of all these long acting medicines are nausea, vomiting, abdominal pain and diarrhea. These side effects usually disappear within a few weeks, and are less likely to happen if they are started at a low dose and increased gradually. Occasionally they are persistent. Some somewhat less common side effects include headache, fatigue, dizziness, constipation, heartburn, bloating, belching and flatulence (passing gas). People with diabetes can sometimes get low blood sugar. Again, most of these side effects usually go away within a week or two. Occasionally they can be persistent.
Rare Side Effects
These side effects are rare, but much more serious and can result in hospitalization. They include severe allergic reaction, acute pancreatitis, gall stones, acute kidney injury, suicidal thinking, and cancer of the thyroid.
Long Term Effects
The evidence so far is that stopping these medicines results in weight gain back to the original weight. That means that people are likely to have to stay on these medicines to maintain the weight loss. We know that the medicines are relatively safe when taken for two years, but we have no idea what long term side effects might be, or even if the medicines will continue to work past two years.
How well do they work?
The medicines are given by injection once a week and they work very well. These are the most effective medicines for weight loss that we have ever had, and there are some new ones in the pipeline that may even work better. As with any medicine, there are risks as I have documented above as well as benefits. You would not want to take one of these medicines unless the benefit exceeds the risk.
Who should take these medicines and who should not?
Obesity increases the risk of diabetes, heart disease and cancer, especially colorectal cancer. The best predictor of risk of disease from obesity is the waist circumference. Just take a tape measure and measure your waist at the level of the belly button. If you are female your risk of cancer starts to increase if your waist circumference is more than 31.5 inches. Your risk of cancer, especially colorectal cancer increases 5% for every inch above 31.5 inches. Above 35 inches the risk of diabetes, and cardiovascular disease starts to go up. For men the numbers are 37 inches for the risk of cancer going up and 40 inches for the risk of diabetes and cardiovascular disease.
The best treatment for obesity is prevention. That means eating unprocessed foods and regular exercise. If you are already overweight or especially if you are obese, it is very hard to lose weight and keep it off. Once you lose weight, your body thinks it is starving and all kinds of hormones and body changes kick in to try to get the weight back.
If your waist circumference is over 31.5 if your are female and 35 if you are male, then you are a candidate for one of these new weight loss medicines. For you the benefit likely outweighs the risk. If your waist circumference is less than those values, then the risk of taking these medicines is much higher than the potential benefit.
Cost
If your insurance does not cover medicines for weight loss the cost of these medicines may be prohibitive.
Wegovy costs $1,349.00 a month without insurance.
Ozempic costs $892.00 a month without insurance.
Muanjaro costs $1,300 a month without insurance.
Unfortunately many insurance plans do not cover weight loss medicines.
First, let me be clear about the definition of cancer screening. Screening for cancer is done for people who feel well and have no symptoms that suggest they might have cancer.The goal is to detect cancer early, before you have symptoms, so that hopefully it is easier to treat and cure.
If you have symptoms of cancer, then tests such as mammograms or colonoscopy are for diagnosis of a disease, not screening. If you are a woman who has a breast lump or abnormal uterine bleeding, or a man with a lump in the testicle, or anyone who has rectal bleeding or difficulty swallowing food, or feeling full after just a little food, you need to see your doctor right away and be tested for cancer. Here is a link to a web page from UCSF that has a more comprehensive look at symptoms of cancer for which you should see your doctor: 17 Cancer Symptoms You Shouldn’t Ignore.
In this post I am going to write about the available screening tests for cancer. For many cancers there are no good screening tests. A good screening test has to meet several criteria. The first is that it detects a kind of cancer that responds better to treatment when detected early. There are other criteria for a good screening test as well. Here is a link to a web page from the American Medical Society Journal of Ethics that talks about all the criteria for a good screening test: What Makes a Screening Exam “Good”?
I will discuss how well each of them work and how well they fit the criteria for a good screening test. I will also write about the risks of getting cancer screening tests (there are some substantial risks).
Cervical Cancer Screening (and Prevention)
Screening for cervical cancer is the poster child for an effective screening test. It is inexpensive, has no significant risk and detects both cervical cancer and pre-cancerous changes. It develops slowly, so it is an ideal cancer for screening. Early detection leads to much more effective treatment even before cancer develops. Since the 1940’s, when the pap smear was invented, death from cervical cancer has decreased by over 70%.
We have learned a lot about cervical cancer since the 1940’s. We now know that cervical cancer is caused by certain strains of the wart virus, otherwise known as HPV (human papilloma virus). The recommendation used to be that women should have a pap smear every year starting after beginning sexual intercourse. We now know that women under 21 most often clear HPV on their own, and there is no reason to do pap smears before age 21. If the pap smear is normal and the HPV test is negative, then for women 30-65 years of age, it is not necessary to do another one for five years. Women over 65 who have had two previous normal pap smears can stop cervical cancer screening.
Not only can the pap smear and HPV test detect cervical cancer early, but they can detect pre-cancerous changes that can be treated before cervical cancer develops. Even better, there is now a vaccine that prevents HPV and therefore cervical cancer altogether. It is called Gardisil, and should be given to adolescent girls and boys before the age they start having sexual intercourse.
Like other screening tests, most women will not benefit from cervical cancer screening. We would have to do pap smear and HPV screening on 1,140 women for ten years to prevent one death from cervical cancer. That means that 1,140 out of every 1,141 women will not benefit from cervical cancer screening,
Breast Cancer Screening
Mammograms are the primary and most studied screening test for breast cancer. Breast cancer is not as ideal for screening as cervical cancer, because some breast cancers develop very rapidly and can spread aggressively between mammography screenings. That means that some women die from breast cancer even if they get regular mammograms. Mammograms also have a high false positive rate, which can lead to more invasive unnecessary tests such as breast biopsies. The false positive rate for any kind of mammogram, including the newer 3D mammograms is 50% over 10 years!
Mammograms do save lives, but a lot fewer than people think. Here is a table from the US Preventive Services Task Force website that shows the benefits and harms of mammograms every two years for every 1000 women screened.
There are a few things to notice about this table. First, almost all the benefit in lives saved by screening is in the 50-74 age group but more false positives, unnecessary biopsies and overdiagnosis occurs in the group that starts mammography at age 40. The other thing to notice is the number of overdiagnosed breast cancers (overdiagnosed means that these tumors would never result in illness or death from the cancer) are much larger than the number of lives saved in each age category.
What this table says is that 125 women need to be screened with mammography to save one life from breast cancer. That is a great number! On the other hand, for every 47 women screened by mammography one woman gets overdiagnosed with breast cancer that would never harm her. That is a terrible number!
Given all this information, what should women do? Here are the US Preventive Services Task Force recommendations as of 2016. These recommendations are currently being updated, but the new recommendations are not available yet. The USPSTF recommends mammograms every other year, rather than every year. Every other year mammograms cut the risk of false positives in half, but result in the same number of lives saved.
The USPSTF recommends biennial screening mammography for women aged 50 to 74 years.
B
Women aged 40 to 49 years
The decision to start screening mammography in women prior to age 50 years should be an individual one. Women who place a higher value on the potential benefit than the potential harms may choose to begin biennial screening between the ages of 40 and 49 years. . For women who are at average risk for breast cancer, most of the benefit of mammography results from biennial screening during ages 50 to 74 years. Of all of the age groups, women aged 60 to 69 years are most likely to avoid breast cancer death through mammography screening. While screening mammography in women aged 40 to 49 years may reduce the risk for breast cancer death, the number of deaths averted is smaller than that in older women and the number of false-positive results and unnecessary biopsies is larger. The balance of benefits and harms is likely to improve as women move from their early to late 40s. . In addition to false-positive results and unnecessary biopsies, all women undergoing regular screening mammography are at risk for the diagnosis and treatment of noninvasive and invasive breast cancer that would otherwise not have become a threat to their health, or even apparent, during their lifetime (known as “overdiagnosis”). Beginning mammography screening at a younger age and screening more frequently may increase the risk for overdiagnosis and subsequent overtreatment. . Women with a parent, sibling, or child with breast cancer are at higher risk for breast cancer and thus may benefit more than average-risk women from beginning screening in their 40s.
C
Other groups recommend more intensive screening, but screening younger women and screening every year results in less than half a percent more lives saved and markedly increases the harms of screening including false positives and overdiagnosis. My feeling is that the USPTF recommendations make the most sense for women.
Prostate Cancer Screening
Screening for prostate cancer with the PSA (prostate specific antigen) is the most controversial of the cancer screening tests. Overdiagnosis with the PSA test is a huge problem. Autopsy studies done on men who died of other causes find that by age 80 more than half the autopsies show prostate cancer. Many, perhaps most prostate cancers grow so slowly that they will never cause any symptoms. More men die with prostate cancer than from prostate cancer. Overdiagnosis leads to radical prostatectomy for tumors that would never cause symptoms or death. Surgery for overdiagnosed tumors results in permanent urinary incontinence for half of men and sexual dysfunction for most of them. On the other hand, prostate cancer kills one out of every 41 men in the US. A good screening test for aggressive prostate cancer would be a wonderful thing. Unfortunately at this point we do not have such a test.
The US Preventive Services Task Force reviews all the available studies of screening tests and makes recommendations based on that evidence. Here is that review for the PSA test if 1000 men are screened with the PSA test annually for13 years,
Number of Men Affected
Men invited to screening
1000
Men who received at least 1 positive PSA test result
240
Men who have undergone 1 or more transrectal prostate biopsies
Men who initially received active treatment with radical prostatectomy or radiation therapy
65
Men who initially received active surveillance
30
Men who initially received active surveillance who went on to receive active treatment with radical prostatectomy or radiation therapy
15
Men with sexual dysfunction who received initial or deferred treatment
50
Men with urinary incontinence who received initial or deferred treatment
15
Men who avoided metastatic prostate cancer
3
Men who died of causes other than prostate cancer
200
Men who died of prostate cancer despite screening, diagnosis, and treatment
5
Men who avoided dying of prostate cancer
1.3
What this table shows is that of 1000 men screened for 13 years, there will be 100 men diagnosed with prostate cancer, but only 1 life saved as a result of screening and 2 other men who avoid metastatic prostate cancer. The cost of that life saved will be 97 men overdiagnosed with prostate cancer and 220 men that have a prostate biopsy. This is not a pleasant procedure and can sometimes result in complications such as infection, as indicated by the 2 men out of the 220 men that were biopsied that were hospitalized because of the biopsy. Five men out of the 1000 died from prostate cancer anyway despite screening, diagnosis and treatment,
African American men and men with a strong family history of aggressive prostate cancer are at substantially higher risk for aggressive prostate cancer. It is worth considering screening for this group. Men at average risk are more at risk for harm than help from prostate cancer screening, at least with the tests we have available now. The USPTF recommendation is that prostate cancer screening is an individual decision and should be discussed with your doctor.
Colorectal Cancer Screening
Colorectal cancer if caught early is almost 100% curable, but if it is not discovered until it invades the intestinal wall, the cure rate gets progressively worse.
Unlike breast cancer and prostate cancer, which have only one kind of screening test, there are a number of different screening tests for colon cancer. They each have advantages and disadvantages.
FOBT (Fecal Occult Blood Test)
This is the oldest test and also the one that has been studied the most. It is also the least expensive ($5-$10). People who do this test every year, and who have a colonoscopy if they have a positive test have reduced deaths from colorectal cancer by about 27%. That means that out of 1000 people who screen annually with FOBT, there will be 270 fewer deaths from colorectal cancer than people who do not do screening.
The biggest problem with this test is that it has a fairly low sensitivity of 50%, which means it will miss half of early colorectal cancers. It also has a fairly low specificity of 78%, which means that about 1/4 of the tests will be false positives.
FIT (Fecal Immunochemical Test)
This newer test is only positive for blood coming from the colon. That makes both the sensitivity and the specificity higher than FOBT. It is also fairly inexpensive (the home test costs about $25)
The sensitivity of the FIT test is about 75%, which means it will miss about 25% of early colorectal cancers. The specificity of the FIT test is about 90%, which means that the false positive rate is only 10%. Because the FIT test is relatively new, there are no randomized controlled trials of lives saved by FIT tests vs no screening. Estimates based on computer models suggest that annual FIT testing with colonoscopy for positive tests would reduce deaths from colorectal cancer by 74%! That means that of 1000 people who screen with the FIT test and get colonoscopy for positive tests, deaths from colorectal cancer will be reduced from 1782 deaths to 457 deaths.
There are several different kinds of FIT tests. Some require sending a stool sample to a lab, but the home test is just as good and is less expensive. The one that seems to work the best is from Pinnacle Biolabs. Here is a link to their website where you can order a test: Second Generation FIT® 1 Pack.
Cologuard
Cologuard is the only commercially available DNA test. It measures the specific DNA shed by cancer cells. It is actually a combination test and includes a FIT test as well. This increases the sensitivity, but decreases the specificity, which means that the Cologuard test has a higher false positive rate than the FIT test alone. It is also very expensive, about $600 per test. A stool sample has to be collected and sent to the lab. Computer modeling suggests that deaths from colon cancer for 1000 people would be reduced from 1782 deaths to 1143 deaths. Not nearly as good as the FIT test alone.
Colonoscopy
Although some groups consider colonoscopy to be a screening test, many organizations feel that colonoscopy should be used only when another screening test is positive. People who are at high risk of colon cancer should probably have colonoscopy as a screening test. Colonoscopy done every ten years, with follow-up exams every 3 to 5 years when polyps were found, would reduce deaths from 1782 deaths to 624 deaths.
Colonoscopy is the most sensitive and specific test, but also carries much more risk as a screening test. Serious complications (bleeding or perforation) occur in 44 people out of every 10,000. 3 people out of 100,000 die from colonoscopy. The average number of colonoscopies to result in one serious complication is 225. It is also very expensive (average cost $1,700). It may seem counterintuitive that FIT testing saves more lives, but that is because it is easy to do FIT testing every year and screening colonoscopies are done only every 10 years. One advantage of colonoscopy is that it reduces the chance of getting colon cancer by identifying and removing pre-cancerous polyps.
Lung Cancer Screening
For a long time we had no good screening test for lung cancer. Annual chest x-rays were shown to be worthless for lung cancer screening. Now there is a screening test for lung cancer. It is a low radiation dose CT scan. It should be done every year, but only for people aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years.
False positives are a huge problem with lung cancer screening. Of people who get a positive result, 97% of those will be a false positive, meaning no cancer will be found on further testing. Further testing may include a needle biopsy of the lung, which can result in a collapsed lung.
The number needed to screen to prevent 1 lung cancer death is about 300. The number needed to harm (false positives or over diagnosis is 19. Although lung cancer screening with low dose CT does save lives, it comes at a substantial cost of false positives and overdiagnosis.
Common Cancers with No Good Screening Test
There are no good screening tests for ovarian cancer, uterine cancer, pancreatic cancer, esophageal cancer, leukemia, or Hodgkin’s disease (cancer of the lymph nodes. Many of these cancers are treatable once they are found, but they are found because of symptoms, not because of screening.
Galleri test
This is an update to this post, which I just published. Galleri is a new blood test that detects DNA shed by cancer cells. The company claims that it will detect 50 different types of cancer. Although this technology is promising, it is not yet ready for prime time. It is very good at detecting advanced cancer, but not very good at detecting stage 1 cancers when they are most treatable. There is also a high false positive rate of about 30%. Hopefully this technology will improve. If that happens, it will be a game changer with regard to cancer screening.
Bottom Line
If you are higher risk for any of the cancers for which we have screening tests, then getting screened is something you should do. If you are at average or low risk, screening tests are unlikely to help you and may harm you. Everyone should be alert for red flag symptoms that mean you might have cancer. The purpose of this post is not to discourage cancer screening, but to give you information that you should have when making a decision about whether and which cancer screening tests you choose.
Although we talk about cancer as if it were one disease, it is actually many different diseases. Some are common, and some are rare. In this post I’m going to write about the five most common cancers in the United States. I will focus on incidence (how common they are in the population), risk factors for these cancers, and especially risk factors that can be reduced or eliminated. I will not talk about screening for cancer. That will be the subject for another post
Breast Cancer
Breast cancer is the most common cancer in the U.S. The incidence of breast cancer in the U.S. is 128 new cases per 100,00 women per year (men get breast cancer too, but at a much lower rate). That means that one tenth of one percent of women in the U.S get breast cancer every year. The population risk increases with age. The lifetime risk of developing breast cancer is 13 per cent, or about one in eight women. The majority of that risk is in women over the age of 65. Overall, 20% of women with breast cancer eventually die from it. That means the cure rate is 80%.
Things you can do to reduce your risk of getting breast cancer
Eat a high fiber diet with lots of vegetables and avoid lots of red meat, animal fat and processed foods. Studies have shown that this kind diet reduces the risk of getting breast cancer. Of course this kind of diet also reduces the risk of heart disease and stroke as well, as I have written about in previous posts.
Be physically active. Women who are not physically active have a higher risk of getting breast cancer. There are lots of ways to be physically active. Take at least one flight of stairs instead of taking the elevator. Park as far as you can from the store when you are shopping. Take some long walks in your neighborhood if that is safe where you live. If not, drive or take the bus to a nearby park to walk.
Maintain a healthy body weight. Older women who are overweight or have obesity have a higher risk of getting breast cancer than those at a healthy weight.
Don’t take hormones (if you can help it). If you do need hormones for menopausal symptoms, take estrogen only, not estrogen and progesterone and take it for less than 5 years if possible. Some forms of hormone replacement therapy (those that include both estrogen and progesterone) taken during menopause can raise risk for breast cancer when taken for more than five years. Certain oral contraceptives (birth control pills) also have been found to raise breast cancer risk.
Reproductive decisions. Have your first pregnancy before age 30 if possible, and breast feed for as long as is practical whatever age you have children. Having a first pregnancy after age 30, not breastfeeding, and never having a full-term pregnancy can raise breast cancer risk.
Don’t drink alcohol or have no more than one drink per day. Studies show that a woman’s risk for breast cancer increases with the more alcohol she drinks.
Don’t smoke, or quit if you do: Studies show that smoking cigarettes increases women’s risk for breast cancer
Risk Factors for Breast Cancer You Can’t Change
Getting older. The risk for breast cancer increases with age. Most breast cancers are diagnosed after age 50.
Genetic mutations. Women who have inherited changes (mutations) to certain genes, such as BRCA1 and BRCA2, are at higher risk of breast and ovarian cancer.
Reproductive history. Starting menstrual periods before age 12 and starting menopause after age 55 expose women to hormones longer, raising their risk of getting breast cancer.
Having dense breasts.Dense breasts have more connective tissue than fatty tissue, which can sometimes make it hard to see tumors on a mammogram. Women with dense breasts are more likely to get breast cancer.
Personal history of breast cancer or certain non-cancerous breast diseases. Women who have had breast cancer are more likely to get breast cancer a second time. Some non-cancerous breast diseases such as atypical hyperplasia or lobular carcinoma in situ are associated with a higher risk of getting breast cancer.
Family history of breast or ovarian cancer. A woman’s risk for breast cancer is higher if she has a mother, sister, or daughter (first-degree relative) or multiple family members on either her mother’s or father’s side of the family who have had breast or ovarian cancer. Having a first-degree male relative with breast cancer also raises a woman’s risk.
Previous treatment using radiation therapy. Women who had radiation therapy to the chest or breasts (for instance, treatment of Hodgkin’s lymphoma) before age 30 have a higher risk of getting breast cancer later in life.
Exposure to the drug diethylstilbestrol (DES). DES was given to some pregnant women in the United States between 1940 and 1971 to prevent miscarriage. Women who took DES, or whose mothers took DES while pregnant with them, have a higher risk of getting breast cancer.
Hormonal changes from night shift work: Some studies have shown that night shift work may increase the risk of breast cancer.
There is no point in worrying about things you can’t change, but if you are at increased risk for breast cancer from one or more of these risk factors, that might affect your decisions about whether and when to get screening mammograms. More about screening in another post.
Prostate Cancer
Prostate cancer is the second most common cancer in the U.S. It is the most common cancer in men. The incidence of prostate cancer in the U.S. is 113 per 100,00 men per year. That means, like breast cancer for women, about one tenth of one per cent of men will be diagnosed with prostate cancer every year. Like breast cancer, the population risk increases with age. The lifetime risk of developing prostate cancer for a male is 13 per cent or about 1 in 8. That is about the same lifetime risk risk for women for breast cancer. Overall 3.2% of men will eventually die from prostate cancer. That is a cure rate of 96.2%, much higher than for breast cancer. Part of the reason for the low death rate is that many prostate cancers grow so slowly that more men die with prostate cancer than from prostate cancer.
Risk Factors for Prostate Cancer
Things you can do to reduce your population risk of getting prostate cancer
Diet: Once again, a diet low in animal fat, high in unprocessed and high fiber foods, especially cruciferous vegetables like broccoli and cauliflower seem to be especially protective. Tomato based products, which are high in lycopene also seem to reduce population risk of prostate cancer. Soy intake as well as drinking coffee also seems to be protective.
Alcohol. Alcohol intake does not seem to be a a risk factor for prostate cancer. It is a risk factor for some other cancers that I will write about later.
Don’t smoke cigarettes (or marijuana). Smoking both cigarettes and marijuana increase the risk of prostate cancer
Maintain a normal body weight. Like for breast cancer, obesity increases the risk for prostate cancer.
Exercise. While exercise is good for you in lots of ways, it does not seem to decrease the population risk for prostate cancer.
Risk Factors for prostate cancer you can’t change
Age. Prostate cancer rarely occurs before the age of 40, but peaks between age 65 and 74. Autopsy studies have shown that low grade prostate cancer, never diagnosed during life, is extremely common as age increases. In men 71-80 it can be up to 73%! These low grade prostate cancers never caused any symptoms and the men in the autopsy studies died from something else.
Heredity. If family members have had prostate cancer, especially first degree relatives (father, grandfather) your population risk for prostate cancer is substantially increased
Race. Black men are more likely to get prostate cancer and also more aggressive prostate cancer.
Chemical exposure. Exposure to certain chemicals, especially the herbicide agent orange increase the population risk of prostate cancer.
Once again, there is no point in worrying about things you can’t change. Screening for prostate cancer is very controversial. More about that in another post.
Lung Cancer
Lung cancer is the third most common cancer in the U.S. The incidence of lung cancer is 52 per 100,000 per year, which translates to five one hundredths of 1 per cent of the U.S. population per year that will be diagnosed with lung cancer. The lifetime risk of lung cancer is about 6% of people in the U.S. Of those diagnosed with lung cancer, only 23% will live 5 years after diagnosis. That is a much lower cure rate than for breast cancer and prostate cancer.
Smoking. Smoking cigarettes or cigars or smoking a pipe are the biggest risk factor for lung cancer. People who quit smoking before age 40 have a 90% reduction in smoking related diseases including lung cancer. People who quit smoking by age 54 reduce their risk by two thirds. The risk of lung cancer is still somewhat increased for former smokers as compared to never smokers even 30 years after quitting smoking.
Second Hand Smoke. Breathing other smoker’s smoke also increases your risk of getting lung cancer by 20-30%.
Radon. Radon is the second leading cause of lung cancer after smoking. Radon is a naturally occurring gas that forms in rocks, soil, and water. It cannot be seen, tasted, or smelled. It can accumulate in buildings, especially basements. Homes can be tested for Radon and a simple ventilation fan can decrease radon to safe levels. If your house has not been tested for Radon, it should be. You can buy Radon test kits at a hardware store or on Amazon.
Asbestos Exposure. People who have been exposed to asbestos have an increased risk of lung cancer. Asbestos used to be used as insulation in buildings, but has been banned for years. Asbestos is still in some homes. It is of no risk to residents of those homes as long as it is not disturbed. The risk comes when houses that contain asbestos are torn down or re-modeled.
Other Workplace Exposures.
Other carcinogens (cancer-causing agents) found in some workplaces that can increase lung cancer risk include:
Radioactive ores such as uranium
Inhaled chemicals such as arsenic, beryllium, cadmium, silica, vinyl chloride, nickel compounds, chromium compounds, coal products, mustard gas, and chloromethyl ethers
People who have had radiation therapy to the chest for other cancers are at higher risk for lung cancer, particularly if they smoke. Examples include people who have been treated for Hodgkin disease or women who get chest radiation after a mastectomy for breast cancer. Women who have radiation therapy to the breast after a lumpectomy do not appear to have a higher than expected risk of lung cancer.
Air pollution: in cities, air pollution (especially near heavily trafficked roads) appears to raise the risk of lung cancer slightly. This risk is far less than the risk caused by smoking, but some researchers estimate that worldwide about 5% of all deaths from lung cancer may be due to outdoor air pollution.
Personal or family history of lung cancer
If you have had lung cancer, you have a higher risk of developing another lung cancer.
Brothers, sisters, and children of people who have had lung cancer may have a slightly higher risk of lung cancer themselves, especially if the relative was diagnosed at a younger age. It’s not clear how much of this risk might be due to shared genes among family members and how much might be from shared household exposures (such as tobacco smoke or radon).
Researchers have found that genetics seems to play a role in some families with a strong history of lung cancer.
Once again, there is no point in worrying about risk factors you cannot change. There is a screening test for lung cancer for people who are current or former smokers. More about that in another post.
Colorectal Cancer
Colorectal cancer is the fourth most common cancer in the U.S. The incidence of colorectal cancer is about 38 per 100,000 people per year in the U.S. This means that 4 one hundredths of one per cent of people in the U.S. get colorectal cancer every year. The lifetime risk of getting colorectal cancer is about 4% of people in the U.S. Overall, 35% of people who have colorectal cancer eventually die from it giving an overall cure rate of 65%. The risk of death from colorectal cancer is very dependent on the stage of cancer when it is diagnosed. If colorectal cancer is diagnosed when it is localized, the cure rate is 91%. If it is diagnosed when it has already spread to other parts of the body, the cure rate is 15%.
These are exactly the same modifiable risk factors for breast cancer and prostate cancer. Improving diet, maintaining a normal weight, limiting or eliminating alcohol consumption, and not smoking or quitting smoking decreases population risk of three different cancers.
Risk Factors you cannot change
Age. Almost all colorectal cancers occur after the age of 45 and the vast majority of these occur over the age of 50..
Because chance of cure of colorectal cancer is so much greater when diagnosed at an early stage, screening for colorectal cancer can make a big difference. More about this in another post.
Melanoma Skin Cancer
Melanoma of the skin is the 5th most common cancer in the U.S. It is necessary to specify melanoma of the skin, because melanoma can also occur in the retina of the eye or in any other organ that contains melanocytes (pigment cells). These non-skin melanomas are fortunately rare. The incidence of melanoma of the skin is about 23 per 100,000 people per year or 2 one hundredths of 1 per cent per year. Of those people who develop melanoma of the skin, 6.3% eventually die from it, giving a cure rate of 93.7%. The lifetime risk of getting melanoma is about 2 per cent of people in the U.S.
What do skin melanomas look like?
Warning Signs
a new spot on the skin or a spot that is changing in size, shape, or color.
a spot that looks different from all of the other spots on your skin (known as the ugly duckling sign).
The ABCDE rule.
A is for Asymmetry: One half of a mole or birthmark does not match the other.
B is for Border:The edges are irregular, ragged, notched, or blurred.
C is for Color:The color is not the same all over and may include different shades of brown or black, or sometimes with patches of pink, red, white, or blue.
D is for Diameter:The spot is larger than 6 millimeters across (about ¼ inch – the size of a pencil eraser), although melanomas can sometimes be smaller than this.
E is for Evolving: The mole is changing in size, shape, or color.
Exposure to ultraviolet (UV) rays is a major risk factor for most melanomas. Sunlight is the main source of UV rays. Tanning beds and sun lamps are also sources of UV rays.While UV rays make up only a very small portion of the sun’s rays, they are the main cause of the damaging effects of the sun on the skin. UV rays damage the DNA (genes) inside skin cells. Skin cancers can begin when this damage affects the DNA of genes that control skin cell growth.
The pattern and timing of the UV exposure may play a role in melanoma development. For example, melanoma on the trunk (chest and back) and legs has been linked to frequent sunburns (especially in childhood). This might also have something to do with the fact that these areas aren’t constantly exposed to UV light. Some evidence suggests that melanomas that start in these areas are different from those that start on the face, neck, and arms, where the sun exposure is more constant.
Sunscreen
High protection value sunscreens do prevent sunburn, but paradoxically, people who use high protection sunscreens have an increased risk of skin melanoma. Does that mean sunscreens cause melanoma? No, it means that people who use high protective value sunscreens and apply them frequently are more likely to purposely spend time in the sun (sun bathing). The increased ultraviolet exposure overwhelms the protective value of the sun screen. Avoiding sun bathing and using high protective sun screen when you are working outdoors, as well as wearing a hat and protective clothing is the best way to reduce your population risk of skin melanoma (as well as other types of skin cancers.
Be Vigilant
Be aware of the warning signs above. If you have a mole or a skin lesion that meets any of the warning sign criteria, it is worth a trip to the doctor to check it out.
Risk Factors you can’t do anything about
Moles
A mole (also known as a nevus) is a benign (non-cancerous) pigmented tumor. Babies are not usually born with moles; they often begin to appear in children and young adults.
Having many moles: Most moles will never cause any problems, but someone who has many moles is more likely to develop melanoma.
Atypical moles (dysplastic nevi): These moles look a little like normal moles but also have some features of melanoma. They are often larger than other moles and have an abnormal shape or color. (See Signs and Symptoms of Melanoma Skin Cancer for descriptions of how moles and melanomas look.) They can appear on skin that is exposed to the sun as well as skin that is usually covered, such as on the buttocks or scalp. Dysplastic nevi often run in families. A small percentage of dysplastic nevi may develop into melanomas. But most dysplastic nevi never become cancer, and many melanomas seem to arise without a pre-existing dysplastic nevus.
Dysplastic nevus syndrome (atypical mole syndrome): People with this inherited condition have many dysplastic nevi. If at least one close relative has had melanoma, this condition is referred to as familial atypical multiple mole and melanoma syndrome, or FAMMM. People with this condition have a very high lifetime risk of melanoma, so they need to have very thorough, regular skin exams by a dermatologist (a doctor who specializes in skin problems). Sometimes full body photos are taken to help the doctor recognize if moles are changing and growing. Many doctors recommend that these patients be taught to do monthly skin self-exams as well.
Congenital melanocytic nevi: Moles present at birth are called congenital melanocytic nevi. The lifetime risk of melanoma developing in congenital melanocytic nevi is estimated to be between 0 and 5%, depending on the size of the nevus. People with very large congenital nevi have a higher risk, while the risk is lower for those with small nevi. For example, the risk for melanoma is very low in congenital nevi smaller than the palm of the hand, while those that cover large portions of back and buttocks (“bathing trunk nevi”) have significantly higher risks
Lots of irregular or large moles. The chance of any single mole turning into cancer is very low. However, anyone with lots of irregular or large moles has an increased risk for melanoma.
Fair skin, freckling, and light hair
The risk of melanoma is much higher for whites than for African Americans. Whites with red or blond hair, blue or green eyes, or fair skin that freckles or burns easily are at increased risk.
Family history of melanoma
Your risk of melanoma is higher if one or more of your first-degree relatives (parents, brothers, sisters, or children) has had melanoma. Around 10% of all people with melanoma have a family history of the disease.
Personal history of melanoma or other skin cancers
A person who has already had melanoma has a higher risk of getting melanoma again. People who have had basal or squamous cell skin cancers are also at increased risk of getting melanoma.
Having a weakened immune system
A person’s immune system helps fight cancers of the skin and other organs. People with weakened immune systems (from certain diseases or medical treatments) are more likely to develop many types of skin cancer, including melanoma.
Being older
Melanoma is more likely to occur in older people, but it is also found in younger people. In fact, melanoma is one of the most common cancers in people younger than 30 (especially younger women). Melanoma that runs in families may occur at a younger age.
Being male
In the United States, men have a higher rate of melanoma than women, although this varies by age. Before age 50, the risk is higher for women; after age 50 the risk is higher in men.
Xeroderma pigmentosum
Xeroderma pigmentosum (XP) is a rare, inherited condition that affects skin cells’ ability to repair damage to their DNA. People with XP have a high risk of developing melanoma and other skin cancers when they are young, especially on sun-exposed areas of their skin.
Bottom Line
These five cancers account for half of the cancer diagnoses made every year in the U.S. There are other less common types of cancer, only a few of which have screening tests to detect them early. I will write about some of those cancers in my coming post on screening for cancer. While everyone worries about cancer, the majority of people in the U.S. will never get cancer. The lifetime overall population risk for a U.S.male of getting any kind of cancer other than skin cancer is 40%. For women, that lifetime risk is 39%. These risks average together people at high risk and people at low risk. Your population risk could be substantially lower (or higher) than this average risk.
