Oral Contraceptives and Breast Cancer: A Review of the Epidemiological Evidence with an Emphasis on Younger Women


The possibility of increased breast cancer risk related to oral contraceptive use is a major concern to American women and to the scientific community. Breast cancer incidence in Western countries is relatively high and apparently is increasing. That breast cancer appears to be influenced by other hormonally mediated factors leads to the hypothesis that the high rate of exposure to oral contraceptives among American women may also be associated with this increase.

Examination of cancer incidence data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute suggests that there has been an overall increase in the incidence of breast cancer, with increases of the largest magnitude occurring among women over age 50 (according to SEER data, approximately 1.2 percent per year since 1974). Age-adjusted incidence rates for breast cancer in women under the age of 50 have also increased since 1973, but the increases have been of a much smaller magnitude—approximately 0.2 percent per year. The use of mammographic screening, which facilitates the detection of cases that might otherwise have gone unnoticed, or at the least detects cases at an earlier point in time, may explain some of this increase, especially in women over age 50. However, because screening recommendations apply

Kathleen E. Malone is a Research Associate at the Fred Hutchinson Cancer Research Center, and a graduate student at the University of Washington, Seattle, Washington.

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