Combination oral contraceptives and cancer risk.

Substantial evidence exists to suggest that the use of oral contraceptives alters the risk for some types of cancer. Use of oral contraceptives for one year or more will reduce the risk of endometrial cancer and epithelial ovarian cancer by 50%, with the protective effect lasting for at least 10 years. The risk for developing cervical cancer in women who have used oral contraceptives appears to be slightly increased, although two independent studies actually found a protective effect associated with oral contraceptive use. The protective effect was probably related to the increased screening frequency found in oral contraceptive users and not related to a biologically protective effect. Therefore, women should be encouraged to undergo regular Pap tests. Data regarding breast cancer, in general, show no increased risk associated with oral contraceptive use. The latency associated with the development of breast cancer does not allow a definitive conclusion, and further study will be required. Oral contraceptives appear to increase the risk for developing benign hepatocellular adenoma, but not hepatocellular carcinoma.