Parity is associated with better prognosis in ovarian germ cell tumors, but not in other ovarian cancer subtypes

Ovarian cancer is influenced by reproductive factors, with a reduced risk of epithelial ovarian cancer in parous women. Non-epithelial ovarian cancer frequently affects young women and often precedes or occur during the childbearing years. However, the impact of reproductive factors on ovarian cancer survival remains unclear: in epithelial ovarian cancer, data is conflicting and subtype-specific associations have not been examined, and in non-epithelial ovarian cancer, it has not been studied. Using Swedish registers, we evaluated associations between women's reproductive history and cancer-specific mortality by subtype of epithelial and non-epithelial ovarian cancer in 3791 women born 1953 and later, diagnosed 1990-2018. Hazard ratios (HRs) with 95% confidence intervals (95% CIs) were calculated using Cox-proportional hazard models. Parity was associated with a 78% decreased risk of cause-specific mortality in 243 women with germ cell tumors (GCTs) [parous versus nulliparous, adjusted for age at diagnosis: HR 0.22 (95% CI 0.07-0.62)], with a decreased risk with increasing number of births [per birth: HR 0.60 (95% CI 0.38-0.95)]. We found no evidence of associations between parity and cause-specific mortality among the 334 patients with sex-cord stromal tumors, nor among the 3214 patients with epithelial ovarian cancer; neither overall, nor by subtype. In conclusion, in this large, population-based study, parity was associated with a clearly better prognosis in GCTs but not in the other ovarian cancer subtypes. Future research on how hormone exposure impacts GCT development may lead to a better understanding of mechanisms affecting survival. This article is protected by copyright. All rights reserved.