Metformin may reduce basal cell carcinoma risk
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Metformin, even in low doses, may be associated with a decreased risk for basal cell carcinoma, according to a study.
“Metformin is an oral medication used mostly for type 2 diabetes mellitus,” Jonas A. Adalsteinsson, MD, of the University of Iceland, Reykjavik, and the University of Connecticut, Farmington, and colleagues wrote. “It has been shown to have potential when it comes to inhibiting cancer cell proliferation in animal models and, to a limited extent, has been linked with a lower risk of certain types of cancer in humans, such as breast, pancreatic and colon cancer.”
The whole-population case-control study used the Icelandic Cancer Registry and Icelandic Prescription Medicine Register to identify 6,880 patients diagnosed with first-time basal cell carcinoma (BCC), squamous cell carcinoma in situ (SCCis) or invasive squamous cell carcinoma (SCC) in Iceland between 2003 and 2017, as well as 69,620 population controls.
Subjects were considered exposed to metformin if they had filled at least one prescription more than 2 years before diagnosis.
Of those diagnosed with BCC, 4% were exposed to metformin compared with 5.3% of controls, showing a significant association for metformin use vs. non-use and lower BCC risk (adjusted OR = 0.71; 95% CI, 0.61-0.83).
SCCis and SCC diagnosis, however, was not lower in the metformin-exposed populations; 7.5% of those with SCCis and 6.2% of controls were exposed to metformin (adjusted OR = 1.06; 95% CI, 0.84-0.35), while 7.2% of those with invasive SCC and 6.6% of controls were exposed to metformin (adjusted OR = 1.01; 95% CI, 0.78-1.30).
There were no statistically significant dose-dependent relationships for any of the cancer diagnoses.
The study’s limitations included a lack of data on comorbidities, photodynamic therapy use, tanning bed use, UV exposure, smoking status, socioeconomic status or potential confounding medication use.
“While this study does not imply causation, it does suggest an association between metformin use and lower rates of first-time BCC,” the authors wrote. “Furthermore, randomized prospective trials are required to fully understand the effect metformin has on BCC and SCC risk.”