Abstract 762P
Background
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 proceeds, coincides and might occur during the childbearing years. The impact of reproductive factors on non-epithelial ovarian cancer survival has not been studied, and in epithelial ovarian cancer, data is conflicting. Better knowledge of the relationship between reproductive risk factors and their impact on survival might reveal common underlying mechanisms and raise hypothesis for a better understanding of the tumor biology.
Methods
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.
Results
Parity was associated with 78% decreased risk of cause-specific mortality in 243 women with germ cell tumors (GCTs); adjusted for age at diagnosis. Especially malignant teratomas seem to be less deadly among parous women. Among women diagnosed with malignant teratomas at age 30 years and older (n=77), 6% of the parous women died of their disease, compared with 23% of the nulliparous women (p=0.03). 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. Table: 762P
Associations between parity and cause-specific mortality among patients with ovarian germ cell tumors in Sweden 1990-2018. Hazard ratio (HR) and 95% confidence intervals (CIs) from Cox regression models, adjusted for age at diagnosis
| Parity (ever) | n | Mean age at diagnosis | HR | 95% CI (p-value) |
| No | 135 | 27 years | 1.00 | Ref |
| Yes | 108 | 38 years | 0.22 | 0.07-0.62 (p=0.005) |
| Per birth | 0.60 | 0.38-0.95 (p=0.03) |
Conclusions
In this large, population-based study, parity was associated with better prognosis in GCTs but not in the other ovarian cancer subtypes, potentially indicating that parous women develop less aggressive GCTs. Future research on how hormone exposure impact on GCT development may lead to better understanding of potential mechanisms affecting survival.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
This study was supported by the Nordic Cancer Union, the National Cancer Institute, the Uppsala County, Sweden and Lions research fund at Uppsala Akademiska Hospital. I.G. was supported by the Swedish Cancer Society (190109 SCIA and CAN 2016/440) and the GullstrandFoundation, Uppsala County, Sweden.
Disclosure
I. Glimelius: Financial Interests, Institutional, Invited Speaker: Janssen. All other authors have declared no conflicts of interest.