The association between type 2 diabetes mellitus (DM) and colorectal cancer (CRC) has been thoroughly investigated and reports have demonstrated that the risk of CRC is increased in DM patients. The association between DM and the survival of patients with CRC is controversial. Evidence suggests that metformin with its anti-inflammatory effects is a protective factor against the development of CRC among DM patients and that metformin therapy is associated with a better prognosis in patients with DM. In our cohort, we did not find any associations between the presence of DM or metformin and cancer specific survival or any relation to plasma levels of a panel of 40 inflammatory factors and irisin. On the other hand, we identified that the insulin-like growth factor binding protein 7 single nucleotide polymorphism rs2041437 was associated with DM in CRC patients. The dominance of the T bearing genotypes in patients with DM was statistically significant (P = 0.038), with an odds ratio of 1.66 (95% confidence interval: 1.03-2.69).