[The effect of metformin on responses to chemotherapy and survival in stage IV colorectal cancer with diabetes].

Metformin is known to lower the risk of cancer and cancer mortality. However, the effect of metformin in stage IV colorectal cancer (CRC) patients with diabetes mellitus (DM) remains unknown. The aim of this study was to evaluate the effect of metformin on tumor response and survival in stage IV CRC patients with DM. We identified 106 patients who were diagnosed with both stage IV CRC and DM (81 patients who underwent palliative chemotherapy and 25 patients who underwent curative resection). Retrospective data of each patient's clinical characteristics, tumor response, and survival rate were compared between two groups of patients who either were or were not administered metformin. For the palliative chemotherapy group, tumor response, change in target lesion size, progression free survival rate, and overall survival rate were not significantly different between the metformin group and the non-metformin group on univariate and multivariate analysis. For the curative resection patient group, metformin use was associated with increased disease free survival on univariate analysis (p=0.012) and multivariate analysis (hazard ratio, 0.024; 95% CI 0.001-0.435; p=0.010), but not with overall survival. Metformin use in stage IV CRC patients with diabetes was shown to be associated with a lower risk of tumor recurrence after curative resection.