INTRODUCTION: Usage of metformin is associated with improved survival in lung, breast and prostate cancer, and metformin has been shown to inhibit cancer cell growth and proliferation in in vitro studies. Given the lack of clinical data on metformin use in patients with bladder cancer, we aimed to evaluate the role of metformin in their oncological outcomes. METHODS: Medication use data from a prospectively maintained database of 122 patients with non-muscle-invasive bladder cancer treated with intravesical Bacille Calmette-Guerin (BCG), who were recruited under a randomised, double-blinded, controlled clinical trial, was collected and analysed. Kaplan-Meier curves were used to assess overall survival (OS) and disease-specific survival (DSS). RESULTS: At a median follow-up duration of 102 (range 3-357) months, 53 (43.4%) patients experienced disease recurrence and 21 (17.2%) experienced disease progression. There was no significant difference in mortality between patients with and without diabetes mellitus. There was significant difference in OS between patients without diabetes mellitus, patients with diabetes mellitus on metformin and patients with diabetes mellitus but not on metformin (p = 0.033); patients with diabetes mellitus on metformin had the best prognosis. Metformin use was associated with significantly lower DSS (p = 0.042). Other oral hypoglycaemic agents, insulin or statins were not associated with disease recurrence or progression. CONCLUSION Metformin use was associated with improved oncological outcomes in patients with non-muscle-invasive bladder cancer treated with intravesical BCG. Prospective studies with larger patient populations are needed to validate the role of metformin as potential therapy for bladder cancer.
Adjuvants, Immunologic/therapeutic use* ; Administration, Intravesical ; BCG Vaccine/therapeutic use* ; Diabetes Mellitus ; Disease Progression ; Humans ; Male ; Metformin/therapeutic use* ; Neoplasm Invasiveness ; Neoplasm Recurrence, Local ; Prospective Studies ; Retrospective Studies ; Urinary Bladder Neoplasms/drug therapy*