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B3 and skin cancers.

Oral nicotinamide reduced the number of nonmelanoma skin cancers in a high-risk population in a 2015, phase-3 study. Nicotinamide, a form of niacin (vitamin B3) that does not cause flushing, helps protect the skin from ultraviolet (UV) light damage. The vitamin prevents UV-caused ATP depletion so that cells have the energy to repair damaged DNA. It also lessens UV-caused immunosuppression. Ultraviolet radiation damage is the main cause of premalignant actinic keratoses as well as basal-cell carcinomas and squamous-cell carcinomas. In phase 2 trials, the number of actinic keratoses among Australians with sun-damaged skin was 29% lower when participants took 500 mg of nicotinamide once a day for 4 months compared with those taking a placebo and 35% lower when subjects took 500 mg twice a day.

To assess oral nicotinamide's protective effect against nonmelanoma skin cancers, Andrew C. Chen and Australian colleagues enrolled 386 people in their multicenter, double-blind trial (Oral Nicotinamide to Reduce Actinic Cancer [ONTRAC]). All participants were aged 18 years or older and had at least two confirmed nonmelanoma skin cancers in the previous 5 years. The subjects had a mean of 46 to 48 actinic keratoses at baseline. Participants were randomly assigned to take 500 mg twice a day (n = 193) or placebo (n = 193) for 12 months. Dermatologists who were blind to group assignments performed skin-cancer checks at baseline and every 3 months thereafter for 18 months.

At 12 months, the mean number of new nonmelanoma skin cancers was significantly lower in the nicotinamide group compared with the control: 1.8 (336 total cancers) vs. 2.4 (463 total cancers). As in previous studies, the number of actinic keratoses also declined in the nicotinamide group. "By chance, there was a lower rate of sunscreen use from baseline to 12 months in the nicotinamide group than in the placebo groups," say the authors. Consequently, the decreased incidence of skin cancers could not be attributed to a difference in sunscreen use. The authors also noticed a trend of increasing effectiveness in nicotinamide subjects who had greater numbers of skin cancers before the trial.

Nicotinamide has a good safety profile. Chen et al. report that it has been used for years at doses up to 3 g daily with minimal side effects. Unlike niacin, nicotinamide does not cause flushing, itching, hypotension, headaches, or other vasodilatory effects. The minimum and maximum effective doses are unknown, according to the authors; but they note that 1500 mg per day has shown no greater preventive effect on UV-induced immunosuppression that 500 mg per day in other studies.

Chen AC, Martin AJ, Choy B, et al. A Phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention. N Engl J Med. October 22, 2015; 373(17);1618-1626.

Hajdenberg J. In high-risk patients, oral nicotinamide reduced number of new nonmelanoma skin cancers during treatment. Annals Int Med. February 16, 2016;JC 18.

briefed by Jule Klotter

jule@townsendletter.com

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Title Annotation:Shorts; role of nicotinamide in preventing skin cancer
Author:Klotter, Jule
Publication:Townsend Letter
Date:Aug 1, 2016
Words:484
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