Epithelial ovarian cancer and combination oral contraceptives.

The risk of epithelial ovarian cancer in relation to the use of combination oral contraceptives was evaluated in a case-control study of women younger than 60 years. Combination oral contraceptives were used by 35 (26%) of 136 cases and 187 (35%) of 539 controls. The relative risk estimate for combination oral contraceptive use was 0.6 (95% confidence interval, 0.4 to 0.9). The reduction in risk appeared to persist for as long as ten years after use had ceased and to be greater for longer durations of use, but these results were not statistically significant. The findings were not explained by parity or by other identified potential confounding factors. The results suggest that the use of combination oral contraceptives protects against epithelial ovarian cancer.