• Malte Rieken, Evanguelos Xylinas, Luis Kluth, Joseph J Crivelli, James Chrystal, Talia Faison, Yair Lotan, Pierre I Karakiewicz, Maxine Sun, Harun Fajkovic, Marek Babjuk, Alexander Bachmann, Douglas S Scherr, and Shahrokh F Shariat.
• Department of Urology, Weill Cornell Medical College, New York-Presbyterian Hospital, New York, NY; Department of Urology, University Hospital Basel, Basel, Switzerland.
• Urol. Oncol. 2014 Jan 1; 32 (1): 49.e7-14.

ObjectivesEvidence suggests a positive effect of metformin on cancer incidence and outcome. To date, the effect of metformin use on prognosis in urothelial carcinoma of the bladder (UCB) remains uninvestigated. We tested the hypothesis that metformin use affects oncologic outcomes of patients treated with radical cystectomy for UCB.Methods And MaterialsWe retrospectively evaluated 1,502 patients treated at 4 institutions with radical cystectomy and pelvic lymphadenectomy without neoadjuvant therapy. Cox regression models addressed the association of diabetes mellitus (DM) and metformin use with disease recurrence, cancer-specific mortality, and any-cause mortality.ResultsA total of 200 patients (13.3%) had DM, 80 patients (5.3%) used metformin. Within a median follow-up of 34 months, 509 patients (33.9%) experienced disease recurrence, 402 patients (26.8%) died of UCB, and 551 patients (36.7%) died from any cause. In univariable Cox regression analyses, DM without metformin use was associated with increased risk of disease recurrence (hazard ratio [HR]: 1.40, 95% confidence interval [CI] 1.05-1.87, P = 0.02), cancer-specific mortality (HR: 1.60, 95% CI 1.17-2.17, P = 0.003), and any-cause mortality (HR: 1.55, 95% CI 1.18-2.03, P = 0.002), whereas metformin use was associated with decreased risk of disease recurrence (HR: 0.61, 95% CI 0.37-0.98, P = 0.04), cancer-specific mortality (HR: 0.56, 95% CI 0.33-0.97, P = 0.04), and any-cause mortality (HR: 0.54, 95% CI 0.33-0.88, P = 0.01). In multivariable Cox regression analyses, DM treated without metformin use remained associated with worse cancer-specific mortality (HR: 1.53, 95% CI 1.12-2.09, P = 0.007) and any-cause mortality (HR: 1.52, 95% CI 1.16-2.00, P = 0.003) but not disease recurrence.ConclusionsDiabetic patients who do not use metformin appear to be at higher risk of cancer-specific and any-cause mortality than patients without DM. It remains unclear, whether the severity of DM in this group of patients or the use of metformin itself affects outcomes of UCB. The mechanisms behind the effect of DM on patients with UCB and the potential protective effect of metformin need further elucidation.Copyright © 2014 Elsevier Inc. All rights reserved.

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