Authors: Garcia C, Yao A, Camacho F, Balkrishnan R, Cantrell LA
Title: A SEER-Medicare analysis of the impact of metformin on overall survival in ovarian cancer.
Journal: Gynecol Oncol 146(2):346-350
Date: 2017 Aug
PubMed ID: 28499649
Abstract: OBJECTIVE: Determine whether metformin use is associated with improved survival in patients with ovarian, fallopian tube or primary peritoneal cancer. METHODS: All patients with a diagnosis of first epithelial ovarian cancer from 2007 to 2011 in the combined SEER-Medicare database were identified from the SEER registry primary site codes. Comorbidities, procedures and cancer treatment ICD-9 and HCPCS codes were used to search the Medicare claims files. Medication use was determined with National Drug Codes using the Medicare Part D event files. The primary outcome, overall survival, was assessed between metformin users and non-users using a Cox Proportional Hazards survival model. To control for confounding, metformin users were matched to non-metformin users using propensity scores. Effect of dosage on survival was assessed using discrete time survival analysis with pooled logistic regression (PLR). RESULTS: There were 2291 cases that met our inclusion criteria. Of these, 180 (7.9%) had been on metformin. The median age was 73years, with the majority of the population being White (83.5%) and treated with primary surgery (74.1%). Metformin use was not associated with overall survival in the entire cohort (HR 0.96, 95% CI 0.75-1.23) or in the matched sample cohort (HR 0.88, 95% CI 0.66-1.17). However, exploratory regression with time-varying coefficients suggests a protective metformin effect for women alive after 30months follow-up (HR=0.37, 95% 0.16-0.87). CONCLUSION: No statistically significant association was observed between metformin use and overall survival in a matched cohort of 360 ovarian cancer patients. However, exploratory modeling suggests metformin use may be protective in a certain subgroup of patients.