Niacinamide supplementation reduces actinic keratoses in adults with sun damage, studies shows

Summary

Researchers at the University of Sydney, Australia, completed two phase II clinical trials to investigate whether oral nicotinamide (niacinamide), at two different dosages, reduces actinic keratoses (AK) in adults with sun damage. AK is reported to be a strong predictor of non-melanoma skin cancer.

For these studies, researchers recruited healthy, immune-competent adults with 4 or more palpable AK lesions (face, scalp and upper limbs) from dermatology clinics in Sydney. Participants were randomly assigned to take nicotinamide (500 mg) or a placebo twice daily (Study 1) or once daily (Study 2) for 4 months. Participants underwent complete skin examination before randomization, were encouraged to use daily sunscreen, and remained blinded throughout the study. At baseline, 2 and 4 months, palpable AK lesions were identified visually and by touch by a blinded observer, counted and documented on a body grid chart. At baseline and 2 months, full blood count, creatinine, and liver function were assessed.

Study 1 sample size (n=36) was based on clinical judgment as it was the first pilot trial of oral nicotinamide. Study 2 sample size (n=41) was selected to ensure a power of 80% for an effect size of 0.4 (significance level of 0.05; two-sided), allowing for 5% withdrawal. The primary endpoint was the AK count at 4 months. Efficacy was based on intent-to-treat analysis.

Compliance was 94-98%, as measured by number of returned tablets.

Results from Study 1 indicate that, compared to placebo, niacinamide supplementation resulted in a 35% relative reduction in AK count at 4 months (95% CI: 18-48%; P=.0006) with similar results at 2 months. Results from Study 2 indicate niacinamide supplementation resulted a 29% relative reduction in AK count at 4 months (95% CI: 11-44%; P=.005) with smaller but significant differences observed at 2 months. There was no evidence that the relative effect of nicotinamide was modified by baseline AK count (treatment-by-baseline interaction).

The researchers note the mechanism(s) by which nicotinamide might prevent skin cancer or reduce progression of subclinical lesions is unclear, but suggest a role in DNA repair and/or immune protection. Nicotinamide is a substrate and inhibitor of the nuclear enzyme poly-ADP-ribose polymerase, which is centrally involved in DNA repair. Nicotinamide is also reported to be highly immune protective, and immunosuppression plays a key role in the malignant transformation of AK lesions.

These findings suggest nicotinamide (500 mg, once or twice daily, for 4 months) is effective in reducing AK count and shows promise for the prevention of skin cancer in adults with sun damage.