Nicotinamide reduces photodynamic therapy-induced immunosuppression in humans.
BACKGROUND
The immune suppressive effects of topical photodynamic therapy (PDT) are potential contributors to treatment failure after PDT for nonmelanoma skin cancer. Nicotinamide (vitamin B(3) ) prevents immune suppression by ultraviolet radiation, but its effects on PDT-induced immunosuppression are unknown.


OBJECTIVE
To determine the effects of topical and oral nicotinamide on PDT-induced immunosuppression in humans.


METHODS
Twenty healthy Mantoux-positive volunteers received 5% nicotinamide lotion or vehicle to either side of the back daily for 3 days. Another group of 30 volunteers received 500 mg oral nicotinamide or placebo twice daily for 1 week in a randomized, double-blinded, crossover design. In each study, methylaminolaevulinate cream was applied to discrete areas on the back, followed by narrowband red light irradiation (37 J cm(-2) ) delivered at high (75 mW cm(-2) ) or low (15 mW cm(-2) ) irradiance rates. Adjacent, nonirradiated sites served as controls. Delayed-type hypersensitivity (Mantoux) reactions were assessed at treatment and control sites to determine immunosuppression.


RESULTS
High irradiance rate PDT with vehicle or with placebo caused significant immunosuppression (equivalent to 48% and 50% immunosuppression, respectively; both P < 0·0001); topical and oral nicotinamide reduced this immunosuppression by 59% and 66%, respectively (both P < 0·0001). Low irradiance rate PDT was not significantly immunosuppressive in the topical nicotinamide study (15% immunosuppression, not significant), but caused 22% immunosuppression in the oral study (placebo arm; P = 0·006); nicotinamide reduced this immunosuppression by 69% (P = 0·045).


CONCLUSIONS
While the clinical relevance of these findings is currently unknown, nicotinamide may provide an inexpensive means of preventing PDT-induced immune suppression and enhancing PDT cure rates.
Discipline of Dermatology, Bosch Institute, The University of Sydney at Sydney Cancer Centre, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.
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Thanos
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Halliday
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Damian
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000328:Adult; D000368:Aged; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007154:Immune System Diseases / Q000517:prevention & control*; D007108:Immune Tolerance / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D009536:Niacinamide / Q000008:administration & dosage*; D010778:Photochemotherapy / Q000009:adverse effects*; D012621:Seasons; D013607:Tablets; D014374:Tuberculin Test; D014803:Vitamin B Complex / Q000008:administration & dosage*
D013607:Tablets; D014803:Vitamin B Complex; D009536:Niacinamide