Diabetes mellitus and long-term mortality of ovarian cancer patients. A systematic review and meta-analysis of 12 cohort studies.

Ovarian cancer (OC) is the sixth most common cancer among women, and its prognosis is not favorable. Diabetes mellitus (DM) is hypothesized to be associated with a higher mortality in ovarian cancer patients, but evidence is inconsistent. Thus, we aim to investigate if DM is associated with the long-term all-cause and long-term cancer-specific mortality in ovarian cancer patients by synthesizing available epidemiologic evidences. We used 4 electronic databases (PubMed, EMBASE, Web of Science, and Scopus) to search for eligible articles. Title/abstract screening, full-text review, data extraction, and quality assessment were performed by reviewers independently. In meta-analysis, studies reporting risk ratio (RR) or hazard ratio that investigated the association between DM and mortality of OC patients were synthesized by a random-effect model. Subgroup and sensitivity analyses were performed by certain stratification or restrictive rules. Publication bias was assessed by funnel plots and Egger test. Statistical heterogeneity was evaluated by the I-squared value and a chi-squared test for the Cochrane Q statistic. Twelve cohort studies involving 14 outcome measures were included. In overall meta-analysis, the synthesized RR for all-cause mortality was 1.44 (95% CI 1.16-1.79) without substantial statistical heterogeneity (PCochrane  = .145, I2  = 34.1%); the synthesized RR for cancer-specific mortality was 1.44 (95% CI 1.08-1.93) with substantial heterogeneity (PCochrane  < .001, I2  = 90.1%). No publication bias was observed. Our results suggest DM is associated with a higher all-cause and cancer-specific mortality in ovarian cancer patients. Future studies should be done to examine the association between type 1 DM and ovarian cancer mortality.