Shahrekord University of Medical Sciences Epidemiology and Health System Journal 2980-7891 12 1 2025 06 07 The Association Between Metformin Use and Prostate Cancer Incidence and Mortality: A Systematic Review and Meta-Analysis of Case-Control and Cohort Studies 41 49 10.34172/ehsj.26338 EN Moloud Fakhri https://orcid.org/0000-0001-6995-9779 Tayebe Jamshidbeigi https://orcid.org/0000-0002-2080-4618 Ali Hasanpour Dehkordi https://orcid.org/0000-0003-4285-8497 Sepideh Yadollahi Farsani https://orcid.org/0000-0002-6671-4263 Saeid Hematian https://orcid.org/0000-0002-5633-7070 Hassan Nourmohammadi https://orcid.org/0000-0002-5967-3395 Diana Sarokhani https://orcid.org/0000-0002-5118-2735 Zahra Abdan https://orcid.org/0000-0003-3209-5262 Ayda Hasanpour Dehkordi https://orcid.org/0000-0001-8085-4011 Journal Article 10.34172/ehsj.26338 2024 12 23 2025 03 03 Background and aims: Prostate cancer (PCa) is the most common cancer among men, and type 2 diabetes mellitus (T2DM) increases the risk of PCa. This meta-analysis aimed to investigate the association between metformin administration, PCa incidence, and mortality rates. Methods: The inquiry included databases PubMed, Cochrane, Scopus, Web of Science, and Google Scholar search engine and was updated until June 9, 2024. The primary outcome was the effect of metformin on the risk of PCa. Data were analyzed using STATA version 14 software, and statistical significance was determined at P<0.05. Results: The results of 30 studies containing 1655591 men showed no significant relationship between metformin use and prostate neoplasm (OR: 0.94; 95% CI: 0.79-1.11). Additionally, the use of metformin in men aged 60 to 69 (OR: 0.97; 95% CI: 0.86-1.09) and men aged 70 to 79 (OR: 1.11; 95% CI: 0.91-1.35) was not associated with the risk of prostate carcinoma. Metformin use was not related to PCa in cohort studies (OR: 0.88; 95% CI: 0.71-1.08) and case-control studies (OR: 1.07; 95% CI: 0.92-1.25). Moreover, no significant relationship was found between metformin use and prostate carcinoma in Asia (OR: 0.78; 95% CI: 0.52-1.17), Europe (OR: 1.13; 95% CI: 0.96-1.32), or America (OR: 0.94; 95% CI: 0.74-1.20). However, metformin use reduced PCa mortality (HR: 0.83; 95% CI: 0.71-0.98). Conclusion: Although the use of metformin did not reduce the risk of prostate carcinoma, it was associated with a 17% reduction in prostate carcinoma cancer mortality.