The impact of metformin on survival in patients with melanoma-national cohort study.

Purpose: The primary study outcome was melanoma-specific mortality in patients with type 2 diabetes mellitus (T2DM) using metformin.

Methods: Data regarding patients were provided by the Lithuanian Cancer Registry and were linked with National Health Insurance Fund in accordance with unique personal identification numbers during the period of thirteen years.

Results: About 2817 patients met eligibility criteria and were included in the retrospective cohort study. About 163 patients had pre-existing T2DM and 103 of them were treated with metformin. In the multivariable analysis, there was significant risk difference in melanoma-specific survival between diabetic, metformin-using patients, and nondiabetic patients (P=0.02) in favor of metformin users.

Conclusion: Melanoma patients with T2DM treated with metformin had lower risk of melanoma-specific mortality; however, prospective controlled studies are mandatory to confirm this finding.