Therapeutic Use of Metformin in Diabetes and Survival Outcomes in Endometrial Cancer Patients with Diabetes

OBJECTIVES: To compare survival outcomes between endometrial cancer (EC) patients with diabetes who used metformin to those who did not use metformin. MATERIALS AND METHODS: A retrospective cohort study was conducted of EC patients who were diabetes at the time of their cancer diagnosis and had been scheduled for elective surgery at Rajavithi Hospital between 1 January 2003 and 31 December 2013. The patients were excluded if they had type I diabetes mellitus and a history of other cancers. RESULTS: Of 1,262 EC patients in the study period, there was 212 (16.8%) patients who met the inclusion criteria. Among them, 90 (42.5%) were non-metformin users and 122 (57.5%) were metformin users. With a median follow-up of 47 months, the 5-year overall survivals (76.4% vs 77.9%, p=0.959) and the 5-year progression-free survivals (92.6% vs 84.7%, p=0.091) did not significantly differ between the both groups. On Cox proportional-hazards regression analysis, independent prognostic factors for overall survival (OS) were FIGO stage, depth of myometrial invasion, and cervical involvement. Patients with non-endometrioid histology and advanced stage were found to have a significant effect on progression-free survival (PFS). However, metformin used did not predict either OS (HR, 0.99; 95%CI, 0.56-1.73; p=0.959) or PFS (HR, 2.19; 95%CI, 0.86-5.55; p=0.099). CONCLUSION: Overall, a significant effect of metformin on survival outcomes in EC patients with diabetes was not found in the current study. Larger studies with a prospective randomized control design are needed to clarify the benefit of metformin as a strategy for endometrial cancer prevention and treatment.