Forty years after oral contraceptives were introduced in the United States, results of the Women's Contraceptive and Reproductive Experiences (Women's CARE) study of more than 10,000 women nationwide show there is no link between taking birth control pills and breast cancer risk. The study included both white and African American women age 35 to 64, but it did not address the risks and benefits of using oral contraceptives after menopause as hormone replacement therapy.
"Women using oral contraceptives should be reassured from this study, as it confirms that birth control pills do not increase a woman's risk of getting breast cancer," says Kathy Helzlsouer, M.D., M.H.S., professor of epidemiology and oncology at the Johns Hopkins Bloomberg School of Public Health. The investigators also report that several similar studies show oral contraceptives reduce the risks of uterine and ovarian cancers by as much as 40 percent.
"New research should focus on developing an oral contraceptive that helps reduce the risk of breast cancer, without losing its current cancer preventive effects," says Nancy Davidson, M.D., professor of oncology and director of the Breast Cancer Research Program at the Johns Hopkins Kimmel Cancer Center.
The Women's CARE study comes after an analysis of worldwide studies on oral contraceptive use found a slight increase in breast cancer risk among birth control users. In their editorial reviewing the current study, Hopkins experts say the researchers accounted for long-term birth control pill use and a wide range of estrogen and progesterone doses.
While the Hopkins experts conclude that, for most women, the benefits of taking the pill outweigh the risks, they caution, that while rare, oral contraceptives are associated with an increased risk of other conditions, including blood clots, stroke, liver cancer, heart attack in women over 35 who smoke, and cervical cancer in women infected with the human papillomavirus.