Risk factors for synchronous primary endometrial and ovarian cancers

PURPOSE: The incidence of synchronous primary endometrial and ovarian cance r is 2- to W-fold higher than that expected based on the incidence of each cancer alone, We sought to evaluate reasons for this in a case-control stud y. METHODS: We combined data on a maternal history of cancer and reproductive and menstrual factors from 56 women with synchronous multiple primary disea se who had participated in three population-based studies of gynecologic ca ncer. For comparison, we analyzed the same information from 280 women with endometrial cancer alone, 280 with ovarian cancer alone, and 280 without a history of either cancer. RESULTS: The reduced risk of multiple primary disease associated with high parity (2 or more births vs 0: OR = 0.37, 95% Cl, 0.19-76) and long-term us e of oral contraceptives (12 or more months vs none: OR = 0,60, 95% Cl, 0.2 4-1.5) tended to be more pronounced than that associated with endometrial c ancer alone or with ovarian cancer alone. CONCLUSIONS: Though limited by relatively small numbers, our results sugges t that the presence of some common etiologies is a basis for the unusually high co-occurrence of endometrial and ovarian cancers. (C) 2001 Elsevier Sc ience Inc. All rights reserved.