Metformin, in addition to being the first-line therapy for the treatment of diabetes mellitus 2, also has anti-carcinogenic properties, including direct action on tumor cells by targeting their AMPK pathway (which controls metabolism, angiogenesis, inflammation, and stem cells) and inhibition of cancer growth and proliferation secondary to decreasing insulinemia and glycemia. A recent population-based case-control study was conducted in Iceland involving all 6880 people diagnosed between 2003 and 2017 with first-time basal cell carcinoma, invasive squamous cell carcinoma, and squamous cell carcinoma in situ compared to 69,620 population controls. Data analysis showed that use of metformin was associated with a lower risk of developing basal cell carcinoma, even at low doses: OR 0.71%, 95% confidence interval 0.61-0.83. There was no effect demonstrated with regard to invasive squamous cell carcinoma. Risk of squamous cell carcinoma in situ was mildly elevated in the cohort receiving 501-1500mg daily dose of metformin (OR 1.40; 95% CI 1.00-1.96), although the study did not adjust for ultraviolet exposure, skin type, and other comorbidities. This study suggests that metformin may be a useful agent in preventing basal cell carcinoma in people at high risk of developing this malignancy, but additional studies are needed for confirmation.
References: Metformin is associated with decreased risk of basal cell carcinoma