The role of metformin in prostate cancer chemoprevention remains unclear. REDUCE, which followed biopsy-negative men with protocol-dictated PSA-independent biopsies at 2- and 4-years, provides an opportunity to evaluate the link between metformin use and prostate cancer diagnosis with minimal confounding from screening biases.
In diabetic men from REDUCE, we tested the association between metformin use, use of other anti-diabetic medications, vs. no anti-diabetic medication use and prostate cancer diagnosis as well as prostate cancer grade (low-grade Gleason 4-6, high-grade Gleason 7-10) using logistic regression. Of the 540 diabetic men with complete data, 205 (38%) did not report use of any anti-diabetic medications, 141 (26%) reported use of at least one anti-diabetic medication other than metformin, and 194 (36%) reported use of metformin. During the 4-year study, 122 men (23%) were diagnosed with prostate cancer. After adjusting for various clinical and demographic characteristics, we found that metformin use was not significantly associated with total (OR=1. 19, p=0. 50), low- (OR=1. 01, p=0. 96), or high-grade (OR=1. 83, p=0. 19) prostate cancer diagnosis. Likewise, there was no significant association between the use of non-metformin anti-diabetic medications and prostate cancer risk in both crude (OR=1. 02, p=0. 95) and multivariable analysis (OR=0. 85, p=0. 56). Furthermore, the interactions between anti-diabetic medication use and BMI, geographic location, coronary artery disease, smoking, and treatment group were not significant (all p>0. 05). Among diabetic men with a negative pre-study biopsy who all underwent biopsies largely independent of PSA, metformin use was not associated with reduced risk of prostate cancer diagnosis.
Cancer prevention research (Philadelphia, Pa. ). 2015 Sep 09 [Epub ahead of print]
Tom Feng, Xizi Sun, Lauren E Howard, Adriana Vidal, Alexis R Gaines, Daniel M Moreira, Ramiro Castro-Santamaria, Gerald L Andriole, Stephen J Freedland
Urology, Cedars Sinai Medical Center. , Biostatistics, Durham VA Medical Center. , Biostatistics, Durham VA Medical Center. , Surgery, Cedars Sinai Medical Center. , Surgery, Cedars Sinai Medical Center. , Urology, MAYO CLINIC. , Metabolic Pathways and Cardiovascular R&D unit, GlaxoSmithKline Inc. , Division of Urologic Surgery, Department of Surgery, Washington University School of Medicine. , Division of Urology, Department of Surgery, Cedars Sinai