Association between Metformin Use and Mortality after Cervical Cancer in Older Women with Diabetes

Background: To examine the association between metformin use and mortality in patients with diabetes and cervical cancer. Methods: Using Ontario health databases, a retrospective, population-based cohort study was conducted in women with diabetes >= age 66 years diagnosed with cervical cancer between 1997 and 2010. The association between metformin exposure and cervical cancer-specific mortality was examined using Fine-Gray regression models, with noncancer death as a competing risk and cumulative metformin use as a time-varying exposure. The association with overall mortality was examined using Cox regression models. Results: Among the 181 women with diabetes and cervical cancer, there were 129 deaths, including 61 cervical cancer-specific deaths. The median follow-up was 5.8 years (interquartile range 4.2-9.6 years) for surviving patients. Cumulative dose of metformin after cervical cancer diagnosis was independently associated with a decreased risk of cervical cancer-specific mor-tality and overall mortality in a dose-dependent fashion [HR 0.79; 95% confidence interval (CI), 0.63-0.98; and HR 0.95; 95% CI, 0.90-0.996 per each additional 365 g of metformin use, respectively]. There was no significant association between cumulative use of other antidiabetic drugs and cervical cancer-specific mortality. Conclusion: This study suggests an association between cumulative metformin use after cervical cancer diagnosis and lower cervical cancer-specific and overall mortality among older women with diabetes.