cancer prevention

Cancer Prevention

Definition

Preventing the incidence of cancer is complex and involves many factors that ultimately work by avoiding or limiting exposure to carcinogens. Known carcinogens in humans include physical, chemical, viral, and bacterial carcinogens. Physical carcinogens include the hydrocarbon byproducts of cigarette smoke, radiation, and asbestos. Benzene and vinyl chloride are examples of chemical carcinogens. The human papillomaviruses, which play a role in the development of cervical cancer, are viral carcinogens. A bacterial carcinogen is the bacteria, Helicobacter pylori, which has been linked to the cancer B-cell lymphoma, unique to the gastric mucosa. Familial (hereditary) carcinogenesis plays a role in as many as 15% of all human cancers and has been implicated as the cause of some cases of melanoma, breast, colon, and other cancers.

Some factors that place individuals at high risk for the development of cancer can be modified to decrease risk for development. For example, people can make lifestyle and environmental changes to decrease risk. Behavior modification such as dietary changes, exercise, and avoiding exposure to known carcinogens are primary prevention measures that everyone should adopt.

An evolving field, chemoprevention, is the use of vitamins or medicines to prevent cancer development. In 2003, the U.S. Preventive Services Task Force released a report stating that evidence was insufficient to recommend for or against use of vitamin supplements to help prevent cancer. The task force recommended against supplementation with beta carotene because of higher incidence of lung cancer among those who used certain levels of beta carotene supplements.

Chemopreventive agents have the ability to potentially delay and even reverse the sequence of events at the cellular level that change a normal cell to a cancer cell. An example of a chemopreventive agent is tamoxifen, a drug that is effective in preventing breast cancer in women who are at high risk for developing breast cancer. Vaccines for Hepatitis B virus will not only prevent primary Hepatitis B and liver failure, but also liver cancer.

Preventive surgery may be an option for those individuals who are considered to be at high risk of developing cancer because of a genetic or inherited predisposition. Examples of preventive surgery are prophylactic (preventive) mastectomy to reduce risk for breast cancer, and colon polyp removal in individuals at high risk for the development of colon cancer.

In 2003 the American Cancer Society (ACS) estimated that 30,000 cancer deaths were caused by cigarette smoking alone and some 180,000 deaths could be attributed to tobacco use. All cancers caused by smoking cigarettes and by excessive use of alcohol can be completely prevented. Alcohol consumption is another risk factor for cancer. According to the ACS, up to one-third of the more than 555,000 cancer deaths in the United States in 2003 were related to poor nutrition or insufficient physical exercise. A 2003 study reported that women of average weight who walked briskly at least 1 and one-fourth hours per week had a 30% lower risk of breast cancer than women who did not exercise. Many of the more than one million skin cancers that develop annually could be prevented by adopting protective measures from ultraviolet radiation caused by the sun.

Different cancers are associated with different risk factors. While modification of risk factors plays an important role in the prevention of cancer, it is known that some individuals who have one or more risk factors never develop cancer. Others, however, who have no known risk factors, are eventually diagnosed with cancer. Research aimed at identifying additional risk factors for specific cancers continues.