Oh TK, et al. - Researchers performed this population-based cohort study in 2010 via analyzing sample cohort data from the National Health Insurance Service to determine the link between metformin therapy and cancer in adult patients with diabetes. Metformin users were defined as those who had been prescribed repeated oral metformin administration over a period of ≥ 90 days. The primary endpoint was the new development of cancer from January 1, 2011 to December 31, 2015. The study sample consisted of 66,627 adult patients with diabetes, including 29,974 metformin users and 36,653 controls. Findings revealed no link between metformin therapy and the risk of cancer in this patient population—even in the high daily dosage groups of metformin (> 1 g/day). However, possible residual confounders or bias necessitate further prospective, large population-based cohort investigations to verify these findings.