Breast cancer is the most common cancer in women. A major health problem in many parts of the world, it is especially prevalent in developed countries. As a result of large-scale screening of women considered at higher risk, a greater number of breast cancers have been discovered and treated in recent years, even in cases where the women experienced no symptoms. The American Cancer Society (ACS) estimates that in the United States about 203,500 new cases are diagnosed and about 40,000 women die each year from cancer originating in the breast. One in eight American women who live to age 85 will develop this illness at some time during her life. This rate of incidence increases with age, and women 75 years and older are at highest risk.

Obese women are generally at an increased risk of developing breast cancer. Fatty tissue raises estrogen levels and increases estrogen activity in the setting of obesity. Therefore, factors that promote a decrease of obesity are likely to affect breast cancer risk as well.

Hormone therapy exploits some of the chemicals the body naturally produces. For example, some breast cancer cells thrive on the hormone estrogen, which is produced in the ovaries. Hormone therapy slows the growth of such cells by preventing them from using estrogen.

There is a linear relationship between heavy alcohol consumption and breast cancer incidence: with greater intake, there is greater risk. This does not appear to hold true for mild-to-moderate levels of consumption. Consumption of one drink a day increases risk by about 10 percent, and risk continues to increase with increasing intake. The association of alcohol ingestion with breast cancer is the same for premenopausal and postmenopausal women. The association does not vary by whether alcohol is consumed as wine, beer, or liquor. A 12-ounce can of beer, a 5-ounce glass of wine, and one shot of whiskey all contain about the same amount of alcohol. (Breast Cancer, 2003)

Inger Thune and Tormod Brenn conducted a study to investigate whether everyday exercise is related to the risk of breast cancer. During 1974 to 1978 and 1977 to 1983, a total of 25,624 women, 20 to 54 years of age at entry, enrolled in health surveys and answered questionnaires about leisure-time and work activity. During a median follow-up of 13.7 years, they identified 351 cases of invasive breast cancer among the 25,624 women in the cohort. In regularly exercising women, the reduction in risk was greater in premenopausal women than in postmenopausal women, and greater in younger women than in older women. The risk of breast cancer was lower in lean women who exercised at least four hours per week. The conclusion was that physical activity during leisure time and at work is associated with a reduced risk of breast cancer. (Thune, Inger & Brenn, Tormond, 1269-1274)

Because breast tissue exposure to estrogen increases cancer risk, there has been much interest in evaluating the risk of oral contraceptives. Polly A. Marchbanks and Jill A. McDonald conducted a population-based, case-control study to determine the risk of breast cancer among former and current users of oral contraceptives. They interviewed women who were 35 to 64 years old. A total of 4575 women with breast cancer and 4682 controls were interviewed. Conditional logistic regression was used to calculated odds ratios as estimates of the relative risk of breast cancer. The relative risk was 1.0 (95 percent confidence

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