Major Risk Factors and Preventive Measures
for the Most Commonly Diagnosed Cancers
Colorectal Cancer3, 4, 11 - A direct association has been found between high fat intake, especially animal fat or red meat, and colorectal cancer. Similarly, a diet low in fiber, vegetables and fruit has been found to increase the risk of this disease. Up to half the cases of colorectal cancer may be due to dietary factors. Recent studies have found a possible protective effect of calcium and vitamin D in the diet. Studies have also found that low physical activity is associated with colorectal cancer.
A family history of colorectal cancer, specifically in a parent or sibling, increases the risk of colorectal cancer, as does familial adenomatous polyposis (FAP), a rare inherited condition of intestinal polyps. Inflammatory bowel disease such as ulcerative colitis or Crohn's disease has also been associated with an increased risk of colorectal cancer. Some studies have found that alcohol use increases the risk of this cancer, but other studies did not find this. Some recent studies suggest that estrogen replacement therapy and non-steroidal anti-inflammatory drugs such as aspirin may reduce colorectal cancer risk.
Early detection of colorectal cancer increases the chances of survival. The American Cancer Society recommendations for screening tests are in Appendix III.
Lung Cancer3, 4, 11, 12 - Cigarette smoking is the major cause of lung cancer and is estimated to cause 87 percent of lung cancer cases. Environmental tobacco smoke (or second-hand smoking) also increases the risk of lung cancer among non-smokers and is estimated to account for about two percent of the lung cancer cases. Smokers of cigars and pipes also have an increased risk of lung cancer, although to a lesser extent than cigarette smokers. Long-term exposure to high levels of radon gas indoors is also a risk factor, particularly among smokers.
Occupational exposure to asbestos, radon, inorganic arsenic, polycyclic hydrocarbons (soots, tars, mineral oils, coke oven emissions), chromium, chloromethyl methyl ethers (chemical plants, laboratories, polymer production), and vinyl chloride are associated with lung cancer, and smoking combined with exposure to most of these materials compounds the risk. Such occupational exposures are estimated to contribute to13 percent of lung cancers.
Exposure to high levels of ionizing radiation such as from radiation therapy and atomic bomb fallout in Japan increases the risk. Increased vitamins A, C, and E and other micro-nutrients from eating fresh fruits and vegetables may be protective.
Nearly all lung cancer could be prevented by avoiding tobacco. Ten years after quitting, the ex-smoker's initial risk of lung cancer is reduced to half that of a person who continues to smoke. There are no screening tests recommended currently among smokers. It is especially important to prevent tobacco use among young people. Workers' exposure to carcinogenic substances should be minimized and homes with elevated levels of radon should be remediated. Diets high in vegetables and fruits also may decrease the chances of lung cancer. Early detection of lung cancer is difficult because the symptoms do not appear until late in the disease process.
Breast Cancer3, 4, 11, 13, 14 - The risk of breast cancer is increased when close relatives have had breast cancer, particularly a mother or sister. The risk is even higher if the first degree relative with breast cancer was premenopausal and had cancer in both breasts. Some breast cancers in women with a family history may be the result of a specific inherited gene, i.e. BRCA-1 or BRCA-2. Women who have had cancer in one breast have a higher risk of developing a second breast cancer and women with ovarian or endometrial and with benign fibrocystic breast disease confirmed by biopsy also are at higher risk. Early age at the onset of menstruation and late age at menopause are risk factors. Never having children or having the first live birth at a late age are associated with an increased risk of breast cancer. Breast cancer rates are higher among women of higher income, probably largely related to reproductive risk factors.
Large doses of radiation have been associated with breast cancer, but low doses of radiation used today for chest x-rays or mammograms are considered to be of little or no risk. (The benefits of mammography at intervals recommended by the American Cancer Society far outweigh any risk. See Appendix III.) Recent studies have found an increase in breast cancer risk among women who have three or more alcoholic drinks a day. Breast cancer risk also increases with weight and body mass among postmenstrual women. Studies on the relationship of breast cancer risk to dietary fat are inconsistent. Some research relates breast cancer risk to lack of exercise. Long-term exposure to postmenopausal estrogen replacement therapy and oral contraceptive use may increase the risk of breast cancer. Pesticides and other chemicals that mimic or modify the action of estrogens are currently under study by various research organizations.
Given the known risk factors for breast cancer, opportunities for primary prevention are limited. Tamoxifen has been shown to prevent breast cancer in high risk women, and other medications that may have similar benefits but with less serious side effects are under study. For now, early detection (screening) and treatment are the best means to increase breast cancer survival and reduce mortality. Mammography, breast examination by a nurse or physician, and breast self-examination are all methods to detect breast cancer early. Mammography can detect early breast cancers that even very skilled health practitioners may miss. Appendix III contains recommendations from the American Cancer Society for women about using these methods of early detection. Appendix IV has information on the New Jersey Breast and Cervical Cancer Control Initiative which provides for free screening for eligible women in New Jersey. The report, Breast Cancer in New Jersey 1979-1995, provides additional information and is available from Cancer Epidemiology Services, NJ Department of Health and Senior Services.
Prostate Cancer3, 4, 11 - The causes of prostate cancer are mostly unknown. Family history of prostate cancer in a first-degree relative (father or brother) appears to double the risk of prostate cancer. A history of some benign prostatic diseases such as prostatitis and some types of hyperplasia also may increase the risk. Male sex hormone levels such as testosterone may be related to prostate cancer. Various epidemiologic studies suggest that a diet high in animal fat leads to an increased risk, perhaps through influencing hormone levels. Certain occupational exposures such as cadmium and work in farming, rubber manufacturing, and iron and steel foundries have also been associated with prostate cancer in some studies.
It is difficult to prevent prostate cancer because the causes are not well understood. Every man 50 or older should have a digital rectal examination as part of his annual physical checkup. A blood test for prostate-specific-antigen (PSA) may be advisable for many men (See Appendix III.). All men considering or having the screening tests should be fully informed about the implications of a positive test and the benefits and risks of treatment. The report, Prostate Cancer in New Jersey 1979-1996, provides additional information and is available from Cancer Epidemiology Services, NJ Department of Health and Senior Services.