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Cancer Prevention

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Cancer prevention takes two basic forms: early detection and risk reduction. The purpose of early detection is to reduce the mortality associated with a cancer that already exists but has yet to produce symptoms. This is the primary rationale for most cancer screening tests. Click here to learn more about cancer screening .

Risk Reduction

The purpose of risk reduction is to decrease the chances that a cancer will develop in the first place. The more we can learn about what causes cancer, the more likely we are to find ways to prevent it. In the laboratory, scientists explore possible causes of cancer and try to determine exactly what happens in cells when they become cancerous. Researchers also study patterns of cancer in the population to look for risk factors, conditions that increase the chance that cancer might occur. They also look for protective factors, which decrease the risk of cancer.

What researchers do know is that cancer develops over time. It is a result of a complex mix of factors related to lifestyle, heredity, and environment. Some factors that increase a person's chance of developing cancer have been identified. Advancing age is a significant risk factor for most types of cancer. Other risk factors include:

  • Tobacco use
  • Diet
  • Alcohol use
  • Radiation (ultraviolet and ionizing)
  • Chemicals and other substances
  • Estrogens
  • Heredity


Smoking tobacco, using smokeless tobacco, and being regularly exposed to environmental tobacco smoke are responsible for one-third of all cancer deaths in the United States each year. Smoking accounts for more than 85% of all lung cancer deaths. Because the cancer-causing chemicals absorbed from cigarette smoke are transported through the bloodstream and eliminated as waste products, cigarette smoking also causes cancer in organs other than the lung. Thus, cigarette smokers are also more likely than nonsmokers to develop several other types of cancer, including oral cancer and cancers of the larynx , esophagus , pancreas , bladder , kidney , and cervix .

Smoking may also increase the likelihood of developing cancers of the stomach , liver , prostate , colon , and rectum. The risk of cancer begins to decrease soon after a smoker quits, and the risk continues to decline gradually each year after quitting, although rare cases of smoking-related cancer occur in patients who have been “smoke free” for decades.

People who smoke cigars or pipes have a risk for cancers of the oral cavity that is similar to the risk for people who smoke cigarettes. Cigar smokers also have an increased chance of developing cancers of the lung , larynx, esophagus, and pancreas. The use of smokeless tobacco (chewing tobacco and snuff) causes cancer of the mouth and throat . Studies suggest that exposure to environmental tobacco smoke, also called secondhand smoke, increases the risk of lung cancer for nonsmokers.

Smoking also increases the risk of developing cancer in the presence of other environmental factors, such as asbestosis.

Click here if you would like information on how to quit smoking .


While dietary factors clearly have a role to play, the connection between diet and cancer is complex and still not well understood. Some evidence suggests a link between a high-fat diet and certain cancers, like colorectal, uterine , and prostate. Being seriously overweight has been linked to cancers of the breast (among older women), prostate, pancreas, uterus, colon, and ovary . On the other hand, some studies suggest that foods containing fiber may help protect against colorectal cancer, though this has recently come into question.

In the past, some studies suggested that antioxidant vitamins ( C and E ) and minerals ( selenium ) reduce the risk of certain cancers. More recent studies, however, have failed to substantiate these findings.

Recent new evidence suggests that calcium and vitamin D supplementation may lower the risk of cancer. In one recent study, about 1,200 postmenopausal women were randomly assigned to take calcium only, calcium plus vitamin D, or a placebo pill every day. After four years, cancer was diagnosed in 6.9% of the placebo group, but in only 3.8% of the calcium group and 2.9% of the calcium plus vitamin D group.


Heavy drinkers have an increased risk of cancers of the mouth, throat, esophagus, larynx, stomach, colon and breast, and liver. (People who smoke cigarettes and drink heavily have an especially high risk of getting these cancers.) Drinking in moderation (one drink for women and two drinks for men per day) does not appear to significantly increase the risk of cancer.


Ultraviolet radiation (UV) from the sun causes premature aging of the skin and the two most common kinds of cancer—squamous cell and basal cell carcinomas of the skin . Artificial sources of UV radiation, such as sunlamps and tanning booths, also can cause skin damage and may increase cancer risk. UV radiation has also been linked to an especially serious cancer—malignant melanoma —which often appears as a discolored, misshapen mole, and which, if not found and treated early, is especially likely to metastasize and result in death.

To help reduce the risk of skin cancer caused by UV radiation, it is best to reduce exposure to the midday sun (from 10 am to 3 pm) and always wear sunscreen when outdoors for extended periods of time. In addition, if you have a family history of melanoma or other skin cancer, it is also important to have regular skin evaluations by a physician who can check for early signs of cancer development, especially in moles.

Click here if you would like more information on how to reduce your exposure to ultraviolet radiation .

Ionizing radiation from x-ray procedures, radioactive substances, cosmic rays from outer space, and other sources are capable of damaging cells, particularly their replicating DNA. Both short-term intensive exposures and long-term low level exposures may lead to cancer. Studies of survivors of the atomic bomb in Japan show that ionizing radiation increases the risk of developing leukemia and cancers of the breast, thyroid , lung, stomach, and other organs. Click here to learn more about radiation as a cause of cancer .

Radiation therapy for cancer may increase the risk of another cancer developing in the original treatment field at some point in the future. Modern radiotherapy equipment is designed to minimize that risk, but it is still important to talk to your doctor about exactly what those risks are.

Chemicals and Other Substances

Repeated exposure to many chemicals commonly found in the workplace can increase the risk of cancer. Asbestos, nickel, cadmium, uranium, radon, vinyl chloride, benzidene, and benzene are examples of well-known carcinogens in the workplace. These may act alone or together with another carcinogen, such as cigarette smoke, to increase the risk of cancer. For example, inhaling asbestos fibers increases the risk of rare type of lung cancer, which is especially high for asbestos workers who smoke. It is important to follow work and safety rules to avoid or minimize contact with dangerous materials. In general, employers are required to provide employees with information (MSDS sheets) about dangerous chemicals in the workplace and the ways to protect against exposure. Click here to learn more about carcinogens as a cause of cancer .


Doctors may recommend estrogen alone or in combination with progesterone (hormone replacement therapy) to control menopausal symptoms (such as hot flashes and vaginal dryness). Some studies have shown that the use of estrogen alone increases the risk of cancer of the uterus, which can be avoided by adding progesterone. Using both, though, has been recently shown to increase the risk of breast cancer along with other adverse effects. Because it is no longer clear that the risks of hormone replacement therapy outweigh the benefits, be sure to carefully review your options with your physician.

Click here if you would like more information on hormone replacement therapy (HRT) .

Diethylstilbesterol (DES) is a synthetic form of estrogen that was used by pregnant women between the early 1940s and 1971 to reduce the risk of miscarriage. Later on, it was discovered that the DES-exposed daughters of these women had an increased risk of developing a rare type of vaginal cancer, and DES-exposed sons had an increased risk of having undescended testes , which is a condition associated with the development of testicular cancer in males.


While all of us are more or less genetically predisposed to certain cancers, some families have a much higher risk for certain cancer (such as melanoma and cancers of the breast, ovary, prostate, and colon) than the general population. If you have more than one first degree relative (sibling or parent) who developed cancer at a relatively young age (under 55), you may be a member of a cancer-prone family. If this is the case, you might benefit from genetic screening (if available) and closer surveillance, or, in some cases, prophylactic surgery (removal of an at-risk organ before cancer develops because the risk is so high). Click here for more information on cancer screening .

Revision Information

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  • Defining cancer. National Cancer Institute website. Available at: . Accessed August 1, 2008.

  • Detailed guide. American Cancer Society website. Available at: . Accessed August 1, 2008.

  • Finley RS, Balmer C. Concepts in Oncology Therapeutics . 2nd ed. Bethesda, MD: American Society of Health-System Pharmacists;1998.

  • Fox SI. Human Physiology . 4th ed. Dubuque, IA: William C. Brown Publishers; 1993.

  • 7/5/2007 DynaMed's Systematic Literature Surveillance DynaMed's Systematic Literature Surveillance : Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. 2007;85:1586-1591.