Reproductive factors of ovarian and endometrial cancer risk in a high fertility population in Mexico

A case-control study was carried out in Mexico City during 1995-1997 among women with epithelial ovarian cancer (84 cases) and endometrial cancer (85 cases). The control group consisted of 668 healthy women, matched according to age categories. In a multivariate analysis, the reproductive risk facto rs for ovarian and endometrial cancer are similar. The risk of ovarian canc er was inversely related to the number of full-term pregnancies; the odds r atio (OR) was 0.17 and the 95% confidence interval (CI) was 0.05-0.54 when comparing nulliparous women versus those with more than seven pregnancies. For endometrial cancer, a similar association was observed (OR, 0.11; 95% C I, 0.04-0.34). The use of oral contraceptive hormones was inversely associa ted with both ovarian (OR, 0.36; 95% CI, 0.15-0.83) and endometrial cancer risk (OR, 0.36; 95% CI, 0.14-0.90). In women with a history of more than 8. 7 years without ovulation, the risk of ovarian cancer decreased four times (OR, 0.23; 95% CI, 0.10-0.50), and that of endometrial cancer decreased mor e than five times (OR, 0.17; 95% CI, 0.08-0.35). These two neoplasms are cl early typified as hormone dependent, and it is possible to establish that " ovulation" and "exfoliative" mechanisms jointly determine the level of risk for both ovarian and endometrial cancer.