Impact of Glycemic Control and Metformin Use on the Recurrence and Progression of Non-Muscle Invasive Bladder Cancer in Patients with Diabetes Mellitus

The purpose of the present study was to determine the potential relationships of glycemic control and use of metformin with non-muscle invasive bladder cancer characteristics. We reviewed data from 645 patients with non-muscle invasive bladder cancer between January 2004 and May 2015. We analyzed the association of pre and post-operative glycemic control and use of metformin with clinical characteristics of bladder tumors. We also analyzed the association of glycemic control and use of metformin with recurrence-free and progression-free survivals. Diabetes mellitus patients showed decreased recurrence-free survival (hazard ratio 1.42; 95% confidence interval 1.1–1.9; P = 0.021) and progression-free survival (hazard ratio 1.79; 95% confidence interval 1.1–2.8; P = 0.013). Diabetes mellitus patients with a HbA1c ≥ 7.0% demonstrated a higher rate of progression (P = 0.026). Kaplan-Meier analysis showed that progression-free survival rate was associated with poor baseline glycemic control (P = 0.026) and post-operative glycemic control (P = 0.025). However, use of metformin had no impact on the recurrence (P = 1.00) and progression (P = 0.282). In conclusion, poor baseline and post-operative glycemic control was related with shorter progression-free survival of patients with non-muscle invasive bladder cancer. Use of metformin had no impact on the recurrence and progression. Therefore, tight glycemic control and close follow-up for bladder tumor may be beneficial in patients with poor glycemic control.