Metformin in Colorectal Cancer: Epidemiological Evidence, Predictive Biomarkers, and Implications for Prevention and Treatment.

Interest in metformin as a potential anticancer agent for colorectal cancer (CRC) has increased. However, compelling epidemiological links and strong preclinical evidence suggest that metformin has variable efficacy in patients with CRC. This variability highlights the need to identify the patients who are most likely to benefit from effective stratification. We aimed to review the evidence concerning the diverse roles of metformin in CRC prevention and treatment, focusing on identifying and validating the predictive biomarkers essential for selecting patient subgroups that are likely to respond positively. We explored the various molecular pathways through which metformin acts and investigated how these diverse mechanisms might explain the observed differences in patient responses. Epidemiological studies and large meta-analyses have consistently reported reduced CRC incidence and improved survival among patients with diabetes treated with metformin. However, successfully extending these benefits broadly across all patients with CRC or achieving predictable outcomes in advanced disease settings remains a significant challenge. This review consolidates the current knowledge, highlights how different mechanisms interact, critically assesses clinical evidence in light of patient heterogeneity, and advocates for the development and implementation of biomarker-guided personalized therapeutic strategies as key to optimally utilizing the potential of metformin in CRC management. The current challenges and vital future research priorities in this critical area are also outlined.