Metformin is associated with decreased risk of basal cell carcinoma: A whole-population case-control study from Iceland.

Abstract Background Metformin has anti-carcinogenic properties and is also known to inhibit the Sonic hedgehog pathway, but no population-based studies exist analyzing the potential protective effect for basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Objectives To delineate the association between metformin use and invasive SCC, SCC in situ (SCCis) and BCC. Methods A population-based case-control study design was employed using all 6,880 patients diagnosed in Iceland between 2003-2017 with first-time BCC, SCCis and invasive SCC, and 69,620 population controls. Multivariate odds ratios (ORs) were calculated using conditional logistic regression. Conclusion Metformin is associated with decreased risk of BCC development, even at low doses. Metformin might have potential as a chemoprotective agent for patients at high risk of BCC, although this will need confirmation in future studies.