Randomised, double-blind, placebo controlled study to assess efficacy of oral nicotinamide (500mg daily) in the treatment and prevention of actinic keratoses.

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More than 50% of all Caucasian Australians will develop non-melanoma skin cancer (NMSC) during their lifetime, and more than one in 30 will develop melanoma. Ultraviolet radiation (UVR) from sunlight is the major cause of NMSC. In humans, both the ultraviolet A (UVA) and ultraviolet B (UVB) wavebands cause immunosuppression and DNA damage and therefore both UVA and UVB are likely to contribute to induction and development of NMSC. Broad-spectrum sunscreens, which filter both UVB and UVA can reduce UV immunosuppression, but sunscreens are generally much better at preventing sunburn than immunosuppression. As immunosuppression can occur with less than half the amount of UV needed to cause sunburn, the immune protection afforded by sunscreens “in the field” is likely to be low. Oral nicotinamide (vitamin B3) is available as an over-the-counter vitamin supplement and has been effective for over 50 years in the treatment of autoimmune and inflammatory skin disorders including bullous pemphigoid and rosacea. Unlike nicotinic acid, nicotinamide does not cause significant vasodilation or flushing and has few or no potential side effects. The most commonly used dose in autoimmune blistering disorders is 1500mg daily, with these patients often taking nicotinamide for several months. Adverse effects are exceptionally rare at these doses. In mice, nicotinamide reduces skin cancer numbers by 60% when applied as a 2.5% lotion. Our group has demonstrated that nicotinamide lotion completely prevents UV immunosuppression when applied in a double-blinded placebo-controlled manner to the backs of healthy human volunteers. We subsequently found that oral nicotinamide was also immune protective in healthy, Mantoux-positive volunteers, without adverse effects, at doses of either 500mg daily or 1500mg daily. Recently, we tested topical 1% nicotinamide on numbers of actinic keratoses, and found a significant reduction in numbers of keratoses at 3 months compared to placebo. We now plan to assess the effects of oral nicotinamide at an intermediate dose (500mg daily) on AK numbers. We hypothesise that nicotinamide will be well-tolerated, and could be used together with sunscreens to reduce UV immunosuppression and potentially treat or prevent actinic keratosis, premalignant lesions which act as a surrogate marker for squamous cell skin cancers.

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