Reproductive hormones and cancer: ovarian and colon cancer.

Evidence continues to accumulate that oral contraceptive use provides substantial protection against ovarian cancer. Less clear is whether the benefit affects women with genetic predisposition or women in the perimenopausal age range. The role of hormone replacement therapy in the occurrence of ovarian cancer is unclear. Available evidence suggests that if there is any potential risk, it involves women who use estrogen alone. Few women if any entering the menopause are at risk. There is some evidence that oral contraceptives have a favorable impact on the risk of colorectal cancer. Available data are limited. Finally, there is growing evidence that hormone replacement therapy reduces risk of colorectal cancer, a benefit that accrues to perimenopausal women.