Nicotinamide, a form of vitamin B3, was associated with fewer new keratinocyte skin cancers in veterans with a history of the disease. The strongest effect was observed when treatment began following the first cancer, with subsequent cancers occurring at about half the rate compared with unexposed patients. The treatment was linked with fewer squamous cell carcinomas but did not reduce basal cell carcinomas overall.
The analysis included 12,287 veterans who filled a prescription for nicotinamide 500 mg twice daily for more than 30 days. They were compared with 21,535 unexposed veterans matched by the number and timing of prior cancers, as well as demographic and clinical factors. The hazard ratio (HR) for any new skin cancer was 0.86. For squamous cell carcinoma, the HR was 0.78 overall and 0.44 when therapy began after the first cancer. For basal cell carcinoma, the HR was 1.00, showing no overall difference.
Among solid organ transplant recipients, no overall reduction was observed. However, in those with one or two prior cancers, nicotinamide was associated with fewer squamous cell carcinomas. Veterans without other chemopreventive treatments, such as acitretin or field therapy, also showed lower cancer rates with nicotinamide.
Shorter treatment courses were still associated with benefit. Patients prescribed 30 to 90 days of therapy had lower cancer rates, and differences were detectable within the first month of use.
“Timing of treatment was a crucial variable in our study, with patients experiencing benefit only when initiated after the first few skin cancers and then a gradual attenuation of the protective effect," noted lead author, Kimberly F. Breglio, MD, DPhil, of Harvard Medical School and the Veterans Affairs Boston Healthcare System and colleagues.
The study was a retrospective cohort analysis using Veterans Affairs health system data from 1999 to 2024. Patients with at least one prior skin cancer were identified through diagnostic and procedural codes. The primary outcome was time to the next skin cancer, excluding cases within 90 days of baseline to prevent counting preexisting lesions. Propensity score matching balanced exposed and unexposed groups by number and timing of prior cancers, age, sex, race, and other risk factors.
Limitations included reliance on administrative codes for cancer classification, exclusion of events during the first 90 days that created a period of immortal time, and a predominantly older White male cohort, which may limit generalizability. Over-the-counter nicotinamide use outside the health system was not captured, creating potential exposure misclassification. As an observational study, causality cannot be established.
Full disclosures can be found in the study.
Source: JAMA Dermatology
