Pelvic inflammatory disease and the risk of ovarian cancer: a meta-analysis

Previous studies on pelvic inflammatory disease (PID) and the risk of ovarian cancer have found inconsistent results. We performed an updated meta-analysis to summarize the evidence of this association. PubMed, Embase, and ISI web of science databases were searched through October 2016 for studies that investigated the PID and ovarian cancer association. Summary risk estimates were calculated using random-effects meta-analysis. Thirteen studies were eligible for analysis, which included six cohort studies and seven case-control studies. PID was associated with an increased risk of ovarian cancer overall [relative risk (RR) 1.24, 95% CI 1.06-1.44; I (2) = 58.8%]. In analyses stratified by race, a significant positive association was observed in studies conducted among Asian women (RR 1.69, 95% CI 1.22-2.34; I (2) = 0%), but marginally significant among Caucasians (RR 1.18, 95% CI 1.00-1.39; I (2) = 60.7%).Risk estimates were elevated in both cohort (RR1.32; 95% CI 1.05-1.66; I (2) = 64.7%) and case-control studies (RR 1.17; 95% CI 0.93-1.49; I (2) = 57.6%), albeit not statistically significant in case-control studies. Our results suggested that PID might be a potential risk factor of ovarian cancer, with pronounced associations among Asian women. Large and well-designed studies with objective assessment methods, such as hospital records, are needed to confirm the findings of this meta-analysis.