Journal of the American Academy of Dermatology ( IF 13.8 ) Pub Date : 2017-12-13 , DOI: 10.1016/j.jaad.2017.12.016 Chin-Hsiao Tseng
Background
Metformin, an antidiabetic drug, is associated with decreased cancer risk, but its effect on skin cancer is unknown.
Objective
To evaluate skin cancer risk associated with metformin use.
Methods
In total, 16,237 matched pairs of ever and never metformin users with new-onset type 2 diabetes diagnosed during 1999-2005 were retrospectively enrolled and followed until December 31, 2011, using Taiwan’s National Health Insurance database. Hazard ratios (HRs) were estimated using Cox regression weighted for propensity scores.
Results
Skin cancer incidence was 45.59 and 83.90 per 100,000 person-years among ever and never users, respectively (HR 0.540, 95% confidence interval [CI] 0.357-0.819). Among ever users, the HRs (95% CIs) for the first (<21.00 months), second (21.00-45.83 months), and third (>45.83 months) cumulative duration tertiles were 0.817 (0.448-1.489), 0.844 (0.504-1.412), and 0.114 (0.036-0.364), respectively, and the HRs (95% CIs) for the first, second, and third cumulative dose tertiles were 1.006 (0.579-1.748), 0.578 (0.317-1.051), and 0.229 (0.099-0.530), respectively. HRs (95% CIs) were 0.523 (0.175-1.562) for melanoma and 0.496 (0.319-0.772) for nonmelanoma skin cancer.
Limitations
Few patients had skin cancer and information on ultraviolet light exposure and tumor histopathology was lacking.
Conclusion
Metformin use is associated with a decreased skin cancer risk.