Common Cancers: How to Decrease Your Population Risk

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%.

Risk Factors for Breast Cancer (from the CDC)

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.

Risk Factors for Lung Cancer (American Cancer Society)

Risk Factors you can change

• 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
  • Diesel exhaust

Risk Factors you cannot change

• Previous radiation therapy to the lungs
• 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%.

Risk Factors for Colorectal Cancer (CDC)

Risk Factors you can change

• Lack of regular physical activity.
• A diet low in fruit and vegetables.
• A low-fiber and high-fat diet, or a diet high in processed meats.
• Overweight and obesity.
• Alcohol consumption.
• Tobacco use.

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..
• Inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
• A personal or family history of colorectal cancer or colorectal polyps.
• A genetic syndrome such as familial adenomatous polyposis or hereditary non-polyposis colorectal cancer (Lynch syndrome).

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.

Here are a few pictures of actual skin melanomas

Risk Factors (American Cancer Society)

Risk Factors you can do something about

Ultraviolet Light Exposure.

• 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.