Table 5. Key points.

An epidemiological association has been reported between diabetes mellitus, especially type 2 diabetes mellitus , and colorectal cancer However, the association has evolved over time, there are differences between countries over the impact of sex, and colorectal cancer remains uncommon in many countries with a high prevalence of diabetes, suggesting the existence of poorly understood modifiers. The mechanistic basis for this association are poorly understood There are common risk factor for colorectal cancer, diabetes and diabetic complications There are controversial observational data on the association of antidiabetic drugs with colorectal cancer. The most convincing evidence is on a protective effect of metformin Preclinical data suggest that the diabetic environment may promote both colorectal cancer and diabetic complications. There is evidence derived from interventional preclinical studies, GWAS studies, and some interventional clinical data that suggest that CRC and well-characterized complications of diabetes, such as diabetic kidney disease, may share pathogenic pathways, including inflammatory mediators, an abnormal microbiota and altered iron metabolism, some of them converging at Wnt/β-catenin signaling and MIR-21. The finding of common pathogenic pathways for colorectal cancer and diabetic target organ complications (e.g. diabetic kidney disease) lend biological plausibility to the epidemiological observation However, to date no clinical practice consequence has derived from this knowledge