Carcinogenesis related to intense pulsed light and UV exposure: an experimental animal study

This study examines whether intense pulsed light (IPL) treatment has a carcinogenic potential itself or may influence ultraviolet (UV)-induced carcinogenesis. Secondly, it evaluates whether UV exposure may influence IPL-induced side effects. Hairless, lightly pigmented mice (n=144) received three IPL treatments at 2-week intervals. Simulated solar radiation was administered preoperatively [six standard erythema doses (SED) four times weekly for 11 weeks] as well as pre- and postoperatively (six SED four times weekly up to 26 weeks). Skin tumors were assessed weekly during a 12-month observation period. Side effects were evaluated clinically. No tumors appeared in untreated control mice or in just IPL-treated mice. Skin tumors developed in UV-exposed mice independently of IPL treatments. The time it took for 50% of the mice to first develop skin tumor ranged from 47 to 49 weeks in preoperative UV-exposed mice (p=0.94) and from 22 to 23 weeks in pre- and postoperative UV-exposed mice (p=0.11). IPL rejuvenation of lightly pigmented skin did not induce pigmentary changes (p=1.00). IPL rejuvenation of UV-pigmented skin resulted in an immediate increased skin pigmentation and a subsequent short-term reduced skin pigmentation (p<0.002). Postoperative UV radiation resulted in re-pigmentation of IPL-induced pigment reduction (p=0.12). No texture changes were observed. Postoperative edema and erythema were increased by preoperative UV exposure (p<0.002). IPL rejuvenation has no carcinogenic potential itself and does not influence UV-induced carcinogenesis. UV exposure influences the occurrence of side effects after IPL rejuvenation in an animal model.