Estrogen replacement therapy and fatal ovarian cancer.

The authors examined the relation between use of estrogen replacement therapy and ovarian cancer mortality in a large prospective mortality study of 240,073 peri- and postmenopausal women, none of whom had a prior history of cancer, hysterectomy, or ovarian surgery at enrollment in 1982. During 7 years of follow-up, 436 deaths from ovarian cancer occurred. Cox proportional hazard regression was used to adjust for other risk factors. Ever use of estrogen replacement therapy was associated with a rate ratio for fatal ovarian cancer of 1.15 (95% confidence interval (CI) 0.94-1.42). The mortality rate ratio increased with duration of use prior to entry to this study to 1.40 (95 CI% 0.92-2.11) with 6-10 years of use and 1.71 (95% CI 1.06-2.77) with > or = 11 years of use. The increase in mortality associated with > or = 6 years of use was observed in both current users (rate ratio (RR) = 1.72, 95% CI 1.01-2.90) and former users at study entry (RR = 1.48, 95% CI 0.99-2.22), relative to never users. Risk associated with use was not modified by any of the other risk factors. These data suggest that long-term use of estrogen replacement therapy may increase the risk of fatal ovarian cancer.