Oral contraceptives and epithelial ovarian cancer. Does dose matter?

To determine the risk of ovarian cancer among women who use low-estrogen-dose oral contraceptives.

The study used data on white women under 70 years of age who had been enrolled in a population-based case-control study conducted between 1986 and 1988 in three western Washington counties. Women with ovarian cancer (n = 276) were ascertained through a population-based cancer registry, and controls (n = 391) were selected by random digit dialing. Unconditional logistic regression was used to estimate the risk of ovarian cancer associated with oral contraceptive use.

After adjustment for age and parity, women who took oral contraceptives for at least three months were at decreased risk of ovarian cancer (odds ratio [OR] 0.8, 95% confidence interval [CI] 0.5-1.1) relative to women who never used this form of contraception. The reduced risk of ovarian cancer was present among women whose only preparation contained a low (< 50 micrograms ethinyl estradiol or < 80 micrograms mestranol) (OR 0.6, 95% CI 0.3-1.1) and high (OR 0.8, 95% CI 0.5-1.2) estrogen dose.

While our results are limited in their statistical precision and by the inability of many subjects to recall the brands of oral contraceptives that they took, they suggest that the newer, low-estrogen-dose oral contraceptives confer a benefit regarding ovarian cancer risk similar to that conferred by earlier, high-estrogen-dose formulations.