BACKGROUND: Pelvic inflammatory disease (PID) has been proposed as a risk factor for ovarian cancer. However, the existing literature on the association between PID and ovarian cancer risk is inconclusive, and only few cohort studies have been conducted.

METHODS: Using nationwide Danish registries, we conducted a population-based cohort study including all women from the birth cohorts 1940 to 1970 in Denmark during 1978-2012 (n = 1,318,929) to investigate the association between PID and subsequent risk of epithelial ovarian cancer. Among women in the cohort, 81,281 women were diagnosed with PID and 5,356 women developed ovarian cancer during follow-up through 2012. Cox regression models were used to estimate HRs and 95% confidence intervals (CI) for the association between PID and ovarian cancer, both overall and according to histotype.

RESULTS: For ovarian cancer overall, we observed no association with PID (HR, 1.05; 95% CI, 0.92-1.20). However, in histotype-specific analyses, we found a statistically significantly increased risk of serous ovarian cancer among women with PID (HR, 1.19; 1.00-1.41; P = 0.047). Conversely, PID was not convincingly associated with risk of any of the other histotypes of ovarian cancer.

CONCLUSIONS: PID was associated with a modestly increased risk of serous ovarian cancer, but not other histotypes.

IMPACT: Our results indicate that PID is not a strong risk factor for ovarian cancer. Whether PID is slightly associated with risk of serous ovarian cancer has to be confirmed in other studies. Cancer Epidemiol Biomarkers Prev; 26(1); 104-9. ©2016 AACR.