Open Access

ARTICLE

Impact of diabetes and metformin use on prostate cancer outcome of patients treated with radiation therapy: results from a large institutional database

Daniel Taussky^1,2, Felix Preisser^3,4, Pierre I. Karakiewicz^1,5, Derya Tilki^3,4, Carole Lambert^1,2, Jean-Paul Bahary^1,2, Guila Delouya^1,2, Robert Wistaff^2,6, Mikhael Laskine^2,6, Paul Van Nguyen^2,6, Madeleine Durand^2,6, Fred Saad⁵

1 Department of Radiation Oncology, University of Montreal Health Center, Montreal, Quebec, Canada
2 CRCHUM-Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
3 Martini-Klinik, Prostate Cancer Center, University Hospital Hamburg-Eppendorf, Hamburg, Germany
4 Department of Urology, University of Montreal Health Center, Montreal, Quebec, Canada
5 Cancer Prognostics and Health Outcomes Unit, University of Montreal Health Center, Montreal, Quebec, Canada
6 Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
Address correspondence to Dr. Daniel Taussky, Department of Radiation Oncology, Centre Hospitalier de l’Université de Montréal, 1000 rue St Denis, Montréal QC H2X 0C1 Canada

Canadian Journal of Urology 2018, 25(5), 9509-9515.

Abstract

Introduction: Conflicting data exists on the influence of metformin on prostate cancer. We investigated the importance of metformin in patients treated with radiotherapy or brachytherapy.
Materials and methods: All patients from a large institutionalized database, treated for primary localized prostate cancer with either brachytherapy or external-beam radiotherapy ± androgen deprivation therapy were identified. Groups were compared by Kaplan–Meier analyses and Cox regression models. Multivariate analysis was adjusted for CAPRA-Score, type of treatment, and age.
Results: A total of 2441 patients with complete data was identified. Among them, 382 patients (16% of total) were diabetic. Two hundred eighty-one of the 382 diabetics (74%) were treated with metformin and 101 were treated with other anti-diabetic medication. Median follow-up was 48 months (interquartile range [IQR] 24-84). Two hundred eighteen patients (9%) died and 150 (6%) experienced biochemical recurrence (BCR). On unadjusted univariate analysis for BCR-free survival, metformin users showed a 50% reduction in BCR compared to non-metformin users. The results remained significant on multivariate analysis comparing diabetic metformin users to non-metformin users (diabetics and non-diabetics combined) (hazard ratio [HR] 0.5-0.6, p = 0.03-0.04), but lost significance when adjusting for cancer aggressiveness. On multivariate analysis, diabetics had worse overall survival (OS) than non-diabetics (HR 1.5, 95% confidence interval [CI] 1.08-2.06, p = 0.01), but diabetics on metformin fared better than diabetics not taking metformin (HR 0.5, 95% CI 0.26-0.86, p = 0.01).
Conclusion: Metformin use in this analysis appears to be associated with better BCR and OS. Larger datasets and prospective trials are warranted to validate these results.

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