Association of Metformin Treatment with Risk for Death in Diabetic Patients with Concomitant Gastric Cancer

SIMPLE SUMMARY: During the 5-year follow-up within the study period, the cumulative incidence of all-cause death was notably lower in the metformin treatment group compared to the non-treatment group (27.5% vs. 32.8%). The analysis further revealed a significantly reduced hazard ratio (HR) for all-cause death in the metformin treatment group (HR: 0.80, 95% CI 0.78–0.82). This population-based cohort study provides evidence that long-term metformin treatment is associated with a decreased risk of mortality among individuals who have both diabetes and gastric cancer. ABSTRACT: Importance: Despite the existing guideline’s recommendation of metformin therapy as the initial approach for managing diabetes mellitus (DM), there remains a scarcity of comprehensive documentation regarding metformin’s impact on outcomes that are important for patients. Objectives: The objective of this study was to assess the potential impact of metformin treatment on the risk of death in individuals diagnosed with both gastric cancer and pre-existing diabetes mellitus (DM); Design, Setting, and Participants: The study made use of a dataset encompassing nationwide health insurance claims, allowing for a retrospective analysis of all patients with a history of gastric cancer diagnosis (classified under International Classification of Diseases 10th Revision code: C16.X) spanning from 1 January 2002 to 31 December 2012. The primary objective was to observe death within a 5-year follow-up period. The study population comprised 63,664 individuals who fell into two categories: those treated with metformin (n = 29,548) and those who did not receive metformin treatment (n = 34,116). This classification was based on the initial treatment allocation following the diagnosis of gastric cancer. Exposures: Metformin treatment, comorbidities, concurrent medication, and procedural information. Outcomes: All-cause death, disease-specific death, cardiovascular death. Results: During the 5-year follow-up period, the metformin treatment group exhibited a lower cumulative incidence of all-cause death (27.5%) in comparison to the group not receiving metformin treatment (32.8%). Furthermore, the relative hazards for all-cause death were significantly reduced in the metformin treatment group (HR: 0.80, 95% CI 0.78–0.82), indicating a lower risk of death when compared to the non-metformin group. In addition, metformin treatment was associated with lower occurrences of disease-specific death (related to gastric cancer) and cardiovascular death when compared to the group not undergoing metformin treatment. Conclusions: The findings demonstrated that the use of metformin was effective at improving prognosis among gastric cancer patients documented with prior DM. In this population-based cohort study, metformin treatment was associated with reduced risk of mortality.