Clinical Summary

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What was studied

Retrospective cohort of VA patients (1999-2024) comparing those prescribed oral nicotinamide 500 mg twice daily for >30 days (n=12,287) with matched unexposed patients (n=21,479); outcome was time to next skin cancer, including a solid organ transplant subgroup (n=1,334).

Key findings

Overall, nicotinamide was associated with a 14% reduction in skin cancer risk; when started after the first skin cancer, the reduction was 54%, with diminishing benefit when started after later cancers. Within the matched dataset there were 10,994 basal cell carcinomas and 12,551 cutaneous squamous cell carcinomas; the risk reduction was seen for both (greatest for cSCC). Among transplant recipients, no overall significant reduction was observed, though early use was linked to lower cSCC incidence.

Study limitations

Observational EHR-based design from a predominantly older, White, male veteran population (about 2% women) limits generalizability and leaves room for residual confounding despite matching. The abstract does not report absolute rates, hazard ratios, or confidence intervals, and event attribution across exposure groups is not fully clear.

Clinical implications

In this large VA cohort, nicotinamide 500 mg twice daily was associated with lower risk of subsequent skin cancers, especially when initiated after the first skin cancer, with the largest effect in cSCC. Evidence of benefit was not significant overall in solid organ transplant recipients, except for a signal with early initiation for cSCC.