
This study analyzed the potential protective effects of metformin, a common diabetes medication, on non-melanoma skin cancers (NMSC) — basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) — using a large and diverse U.S. health database called All of Us. Skin cancer poses significant risks, particularly in patients with darker skin tones, due to delayed diagnosis and unique risk factors. For example, SCC in African American patients has a much higher metastasis risk (20-40%) compared to sun-induced SCCs in Caucasian populations (1-4%).
The researchers performed a retrospective case-control study with over 4,000 SCC cases and 8,000 BCC cases, each matched to controls of similar age, race, ethnicity, and sex. Propensity score matching and statistical analyses were used to account for confounding factors, such as other medications and health conditions.
Key Findings:
1. BCC Risk Reduction: Metformin significantly reduced the risk of BCC across all groups, boasting adjusted odds ratios (aOR) of 0.33 (95% CI: 0.29–0.36), meaning users were less likely to develop BCC.
2. SCC Risk Reduction: Metformin also reduced SCC risk, with an aOR of 0.45 (95% CI: 0.40–0.51). However, in African American patients, there was no significant reduction in SCC risk, which may be due to SCC’s different causes in this population, such as chronic scarring rather than sun exposure.
3. Protective Mechanisms: Metformin works through several pathways, including inhibiting tumor growth signals, reducing inflammation, regulating abnormal cell growth, and enhancing immune response against cancer cells.
The study emphasized that the results align with previous population-level research but provide new insights, particularly in individuals of different racial and ethnic backgrounds.
Limitations included potential inaccuracies in electronic health records and missing prescription information. Despite these drawbacks, the findings provide compelling support for metformin’s role as a potential preventive treatment against skin cancer, particularly BCC. Further research, particularly prospective studies, is needed to validate these findings, especially among groups with higher SCC risks. If confirmed, metformin might be a cost-effective and widely available preventive strategy for skin cancers.