The impact of metformin use on the risk of prostate cancer after prostate biopsy in patients with high grade intraepithelial neoplasia.

Purpose: We report our experience on metformin use in diabetic patients and its impact on prostate cancer (PCa) after a high-grade prostatic intraepithelial neoplasia (HGPIN) diagnosis. Materials and Methods: We retrospectively analyzed 551 patients with a diagnosis of HGPIN without PCa in a first prostate biopsy. The cohort of the study consisted of 456 nondiabetic subjects, and 95 diabetic patients. Among the patients with diabetes 44 were treated with metformin, and 51 with other antidiabetic drugs. A transrectal ultrasound prostate biopsy scheme with 22 cores was carried out 4-6 months after the first diagnosis of HGPIN. Results: Among 195 (35.4%) patients with cancer, there were statistically significant differences in terms of PCa detection (p<0.001), Gleason score distribution (p<0.001), and number of positive biopsy cores (p<0.002) between metformin users and non-users. Metformin use was associated with a decreased risk of PCa compared with neveruse (p<0.001). Moreover, increasing duration of metformin assumption (>= 2 years) was associated with decreasing incidence of PCa and higher Gleason score >= 7 compared with assumption <2 years. Conclusions: This preliminary experience suggests that metformin use may have some beneficial effects in patients with diabetes and HGPIN; metformin should not be overlooked in these patients because it is neither new nor expensive.