Prevention

Preventing Cancer

Most cancers can be prevented.  This is a key message for a disease that is the public’s number one health fear (1, 2).  Unfortunately, most people remain unclear about the key steps they can take to lower their risk (3). And that’s really not surprising, given the crush of cancer studies and media coverage that we come across week in and week out.  It’s enough to confuse even some experts.

The good news, though, is that when all this evidence is looked at together, eight simple tips rise to the surface. These include things like, maintaining a healthy weight, exercising regularly, and avoiding tobacco. And while there are additional steps on top of these that can reduce the risk of some individual cancers (see Twelve Preventable Cancers), these eight behaviors provide the greatest benefit for the most cancers and can also go a long way toward preventing other serious chronic diseases, like heart disease, stroke, diabetes, and osteoporosis.

It’s almost never too early to help our kids and grandkids build lifelong healthy habits, and it’s almost never too late for adults to start (4, 5).

Also see preventing cancer with the HPV vaccine.

1. Don’t smoke

In the United States, smoking causes approximately 30 percent of all cancers and 90 percent of lung cancers.  About half of all smokers will die from a smoking-related disease, like cancer, heart disease, and chronic obstructive lung disease.  Globally, tobacco causes just over five million deaths a year (6) and is projected to cause 1 billion deaths worldwide by the end of the century (6).

Linked primarily in the public’s mind with lung cancer, smoking and use of smokeless tobacco is an established risk factor for at least 14 other cancers, including cancer of the head and neck, bladder, breast, kidney, cervix, esophagus, pancreas, stomach, colon, rectum, and blood (certain leukemias).

The single best way to prevent cancer and other chronic diseases is not to smoke.  In the United States alone, over 160,000 cancer deaths could be avoided each year if tobacco were somehow miraculously eliminated from the earth (7)

Preventing teens and young adults from taking up smoking provides the biggest health benefits, yet despite stepped up efforts to prevent tobacco use, approximately 18 percent of adults in the United States still smoke (7).  Because of this, efforts to get smokers to stop smoking (cessation) have become increasingly common as well, yet only a small percentage of those trying to quit seek effective treatments that can help them stop (8).  Despite this, cessation has huge benefits.  Within two years of quitting, the risk of many smoking-related diseases begin to drop, and after 10 – 20 years, the risk of lung cancer and most other tobacco-related diseases nearly equals that of non-smokers.

A relatively new addition to the smoking discussion are electronic cigarettes, which are growing immensely in popularity and are often marketed as a safer alternative to standard tobacco cigarettes and as a tool for quitting smoking.  These battery-powered devices go by many different names – including e-cigs, vape pens, personal vaporizers, and hookah pens – and work by aerosolizing a nicotine-containing liquid that is then inhaled.  Though on the face of it electronic cigarettes would appear to be safer than standard tobacco cigarettes, there are many unknown questions about their risks and benefits. Until those questions are answered, avoiding electronic cigarettes is best.  Smokers looking for help quitting should talk to a doctor about FDA-approved cessation aids, like gum, lozenges, patches, and certain medications.

2. Maintain a healthy weight

Although weight is one of the most important risk factors for cancer, a recent survey by the American Institute for Cancer Research found that around half of people are unaware of the link (3, 9).  Very good evidence, though, shows that about 120,000 deaths from cancer could be avoided each year in the United States if everyone stayed at a healthy weight throughout life (10).

Carrying extra weight, particularly being obese (defined as BMI greater than or equal to 30) (BMI calculator), has been strongly linked to an increased risk of cancers of the breast (after menopause), colon, kidney, pancreas, esophagus (adenocarcinoma), ovaries, and prostate. And there is growing evidence that obesity also increases the risk of leukemia, lymphoma, multiple myeloma, and cancers of the liver and gallbladder.

 

The way weight increases cancer risk varies from cancer to cancer.  For example, estrogen produced by fat cells likely increases risk of postmenopausal breast cancer; blood sugar and insulin problems linked to being overweight likely increases risk of colon and pancreatic cancer; and weight-related irritations caused by gallstones and acid reflux likely increase the risk of cancers of the gallbladder and esophagus, respectively.

The now well-known and disturbing trends in the prevalence of overweight and obesity in the United States predict a growing burden of not only weight-related cancers but also heart disease, stroke, and diabetes.  Over the last two decades, rates of obesity have significantly increased across the nation. In 2000, no state had a rate of obesity of 30 percent or higher (11).  Today, 12 states do.  And close to 70 percent of the US population is either overweight (BMI 25 – 29.9) or obese (BMI greater than or equal to 30)(12). Such trends, while most pronounced in the United States, are being expressed worldwide as well, pointing to a huge future global burden from weight-related diseases.

Such numbers demonstrate the need to continue and accelerate weight control efforts that cut across many different parts of society – schools, workplaces, communities, and even social media.  There is a suggestion that such concerted efforts are beginning to have a positive effect in certain groups of children (13). Such progress, though, is just a start and needs to be used to energize further efforts that will have a much broader impact for all.

3. Exercise regularly

The health benefits of regular physical activity are well known.  In addition to lowering the risk of heart disease, stroke, diabetes, osteoporosis, and high blood pressure, it also helps prevent cancer.  Overall, in the United States, it’s estimated that five percent of cancers are linked to lack of regular exercise, which is largely accounted for through the link with two common cancers, breast cancer and colon cancer (14, 15).

For breast cancer, regular exercise lowers risk for both premenopausal and postmenopausal women. Getting out regularly to, say, walk or ride the bike likely lowers risk through multiple ways.  It can improve immune function, which helps the body fight off infections linked to cancer.  It can help maintain healthy levels of hormones (like estrogen and progesterone) in the blood.  And it can help women keep their weight in check.

Growing evidence shows that the earlier regular exercise starts in life, the better it is when it comes to later adult breast cancer risk (16). The time between when a girl starts her period and has her first child is key to the growth and development of the breasts.  During this time, breast tissue seems more susceptible to harmful risk factors, which provides an important opportunity to lower adult breast cancer risk by eating a healthy diet, being physically, and staying at a healthy weight.

For colon cancer, the main mechanism seems to be that exercise can help control insulin levels, which can keep in check certain hormones and growth factors that can promote cancer in colon tissue.

For all its benefits, activity is not the preferred pastime of most people in the United States.  Over 50 percent of the population doesn’t get the recommended amount of activity each week – either 30 minutes of moderate activity (like brisk walking) five or more days per week, or 20 minutes of vigorous activity (like running) three or more days per week (12).  Approximately 30 percent of men and 34 percent of women get very little – or almost no – physical activity during their leisure time (17).

And good evidence now even suggests that regularly being sedentary for long periods –  even if you get recommended amounts of exercise – may increase the risk of breast, endometrial, and lung cancers (18). So, in addition to working toward exercise goals, it’s also important to limit the number of hours spent sitting each day.

4. Eat a healthy diet

A healthy diet is key to overall health and can help lower the risk of many cancers.  While news coverage of the links between diet and cancer have been confusing at best, and misleading at worst, there is solid evidence that the way we eat has a real impact on cancer risk.  Perhaps surprisingly, it’s not fat or meat, or fruits and vegetables that is the most important part of diet when it comes to cancer risk; it’s simply calories (19).  Keeping calories in check, so weight stays in check, is the single most important change in diet people can make.  Outside of calories, good evidence shows that a risk-reducing diet is: largely plant based (with a lot of fruits, vegetables, and whole grains); low in animal products (like animal fat, red meat, and processed meat); low in sodium; and, for men, not too high in calcium (less than 1500mg/day) (20, 21).

A daily multivitamin with folate can provide a nutrition insurance policy as well as added protection against certain cancers and other chronic diseases (21-23).  Folate is a B vitamin that has been shown to lower the risk of colon cancer, as well as breast cancer, in women who regularly drink alcohol.  The calcium and vitamin D in most multivitamins may also help provide added protection against colon cancer (21, 24).

5. Drink alcohol in moderation, if at all

Alcohol has a complex role in health.  While studies consistently show that drinking even a small amount of alcohol (less than one drink/day) can raise the risk of two common cancers (breast and colon), there’s also very good evidence that moderate consumption can significantly lower the risk of cardiovascular disease in older adults (21). Balancing these risks and benefits is key.  Although the benefits of moderate intake in older adults are well established, the cancer risk and potential for alcohol dependence means that non-drinkers should not be encouraged to start drinking.  Most adults who already drink moderately, though, don’t need to stop. All heavy drinkers, though, should be encouraged to cut back to moderate levels, or stop altogether.

Growing evidence strongly suggests that drinking in youth and young adulthood has a particularly important impact on later adult breast cancer risk (25).  Youth should completely avoid alcohol.  Ideally, young adult women should as well; at a minimum, though, if they do drink, they should do so at moderate or lower levels – and avoid binge drinking.

For both breast cancer and colon cancer, alcohol likely increases risk by lowering levels of folate in the body, though there are other possible reasons.  Folate has been shown in some studies to protect against cancer.  The lower levels caused by alcohol may therefore increase risk.  Evidence, though, suggests that taking a folate supplement (like a multivitamin) may help eliminate some of the cancer risk linked to alcohol (26-28).

6. Protect yourself from the sun. And avoid tanning beds

Too much sun exposure is a well-known cause of skin cancer, including serious melanoma. With melanoma rates rising steadily from year to year both in the United States and worldwide, proper sun protection is a key public health message. Yet in the United States, an increasing number of people are experiencing severe sun exposure. The percent of the population reporting a sun burn over the past year is rising, with a third reporting at least one sunburn, and about 20 percent reporting four or more (29).

Tanning bed use is also an important concern, particular in youth and young adults. The International Association for Research on Cancer labels indoor tanning carcinogenic to humans, and the increasing use of indoor tanning closely mimics the rise seen in melanoma rates. One analysis that looked at the results from multiple studies found that any level of use of tanning beds increased the risk of melanoma by around 20 percent (30). If use began before age 35, risk increased even more – by 90 percent.

To lower the risk of melanoma and other types of skin cancer take these steps: never use tanning beds; avoid the sun as much as possible during peak burning hours (10 a.m. – 4 p.m.); wear long sleeve shirts, long pants, and wide-brimmed hats; properly apply (and re-apply when needed) broad-spectrum sun screen; help kids with sun-protection and be a good role model for them.

7. Protect yourself from infections

Although not well known by the general public, infections play an important role in the development of some cancers.  Approximately 23 percent of all cancers in lower income countries are linked to infections.  In higher income countries, this number is seven percent.  In North America, it is four percent (31).

Certain infections can either directly or indirectly cause changes that can lead to cancer. This can happen because of the chronic inflammation that some infections cause or by an infectious agent (like a virus) changing the behavior of infected cells. Infections that compromise the immune system (like HIV) also increase cancer risk by making the body less able to defend against infections that can cause cancer.

Not surprisingly, infection-associated cancers are not a health burden borne equally by all. The poor living conditions and inadequate health care experienced by many people worldwide increase the likelihood of cancer resulting from chronic infections.

There are at least ten infectious agents that are known to increase the risk of cancer (see table), and several of them are quite common. Yet, in most instances, only a small proportion of those infected actually go on to develop cancer because it takes a unique set of factors along with the infection to turn normal cells cancerous.

Still, these infectious agents have a substantial impact on cancer worldwide. Of particular importance are human papillomavirus (HPV), hepatitis B and C viruses, and Helicobacter pylori. HPV is a sexually transmitted virus that is linked to numerous cancers, with cervical cancer being the most important. It’s estimated that almost all cervical cancers are caused by HPV infection. Hepatitis B and C infect the liver and together account for the large majority of liver cancer. Finally, Helicobacter pylori, a bacteria that infects the stomach, has been estimated to cause upwards of 75 percent of all stomach cancers, the fourth most common cancer worldwide.

The promise of prevention is a bright spot when looking at the reach of infection-associated cancers. HPV vaccination of both girls and boys can prevent cervical cancer as well as penile, anal, and throat cancers.  The hepatitis B vaccine – which is growing in use – can prevent liver cancer.  Treatment of Helicobactor pylori likely reduces stomach cancer risk.  And improved screening for and treatment of Hepatitis C may lower liver cancer risk.

Outside of vaccination and treatment, individuals can also lower the risk of infection-linked cancers by taking steps like avoiding blood exposure (by not sharing needles, for example), practicing safer sex and, for women, getting regular Pap tests and possibly HPV tests.

Further advances in vaccines – and in programs that administer them – offer much hope for prevention.

8. Get screening tests regularly

Having cancer screening tests at regular intervals is the single best way to protect against cancer. Not only can screening tests find cancers early when they’re most treatable, in the case of colon and cervical cancer they can actually help prevent the disease.

Screening tests for colon cancer help prevent cancer by finding and removing adenomatous polyps, which are abnormal growths that can go on to become cancer. Regular screening with sigmoidoscopy, for example, has been shown to cut the risk of dying from colon cancer by 30 to 50 percent; fecal occult blood tests can cut colon cancer mortality by up to a quarter (32, 33). And observational studies show that colonoscopy can cut the risk of colon cancer mortality by over half. Although an increasing proportion of adults 50 and older in the United States is actually getting screened for colon cancer, a third of people are still missing recommended tests (12, 34)
Rates of screening are much better for the Pap test, which screens for cervical cancer. Close to 80 percent of the age-eligible women in the United States have had a Pap test within the last three years (12). Pap tests help find abnormal changes in the cells lining the cervix, which could go on to be cancerous. The abnormal cells can then be treated or removed. The Pap test is a huge success story of public health. From the time it became widely used in the 1950’s, rates of death from cervical cancer have dropped by over 70 percent in the United States and other developed nations.
A recent addition to cervical cancer screening is the human papillomavirus (HPV) test, which can be offered to women beginning at age 30 in addition to their regular Pap test. The tests detects whether a woman has an infection with a high-risk type of HPV that is strongly linked to cancer. Women with these high-risk types can then have additional follow-up tests to look for abnormal changes to cells in the cervix.
Outside of prevention, screening tests are key to finding cancer early when it is most treatable. Breast, cervical, and colon screening should be priorities for women. Colon screening should be a prioritiy for men. Current or past heavy smokers between ages 55 and 74 should talk with a doctor about the potential benefits and harms of lung cancer screening with low-dose CT. In addition to the specific tests generally laid out below (see tables), the American Cancer Society recommends that doctors also perform occasional exams for signs of cancer of the thyroid, testicles, ovaries, lymph nodes, oral cavity, and skin (35). Those at increased risk for a specific cancer may need to begin screening earlier, and get screening tests more often, than is recommended for most people. For details on all recommended tests, click here.

Tests for women

Age Test Cancer How often
20-29
Pap test Cervical Every 3 years
Clinical Breast Exam Breast At least every 3 years
Breast Self-Exam Breast OK to do regularly, once in a while, or not all
30-39
Pap test + HPV test Cervical Every 5 years (every 3 years if Pap test alone)
Clinical Breast Exam Breast At least every 3 years
Breast Self-Exam Breast OK to do regularly, once in a while, or not all
40-49
Pap test + HPV test Cervical Every 5 years (every 3 years if Pap test alone)
Clinical Breast Exam Breast Every year
Mammography Breast Every year
Breast Self-Exam Breast OK to do regularly, once in a while, or not all
50 plus
Pap test + HPV test Cervical Every 5 years (every 3 years if Pap test alone)
Clinical Breast Exam Breast Every year
Mammography Breast Every year
Breast Self-Exam

 

Breast

 

OK to do regularly, once in a while, or not all
Low-dose CT Lung Only for current/past heavy smokers, aged 55 – 74 years: Discuss potential benefits/harms with doctor
One of the following:

Colonoscopy

or

Flexible sigmoidoscopy

(can be done along with annual FOBT/FIT)

or

Virtual colonoscopy (CT colonography)

or

Fecal occult blood test (FOBT) or Fecal immunochemical test (FIT)

 

Colon  

Every 10 years

or

Every 5 years

 

 

or

Every 5 years

 

 

or

Every year

  adapted from American Cancer Society, 2014 (35)

Test for Men

Age Test Cancer How often
45-49
Prostate Specific Antigen (PSA) test or Digital rectal exam Prostate For African-American men and others at increased risk:

Discuss potential benefits/harms with doctor

50 plus
Prostate Specific Antigen (PSA) test or Digital rectal exam

 

Prostate For all men:

Discuss potential benefits/harms with doctor

Low-dose CT Lung Only for current/past heavy smokers, aged 55 – 74 years: Discuss potential benefits/harms with doctor
 
One of the following:

Colonoscopy

or

Flexible sigmoidoscopy

(can be done along with annual FOBT/FIT)

or

Virtual colonoscopy (CT colonography)

or

Fecal occult blood test (FOBT) or Fecal immunochemical test (FIT)

 

Colon  

Every 10 years

or

Every 5 years

 

 

or

Every 5 years

 

 

or

Every year

  adapted from American Cancer Society, 2014 (35)

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