Copper vapor laser and photocarcinogenesis in hairless mice

Background and Objective: Port wine stains are commonly located on UV-exposed skin areas. We therefore examined the longterm interaction between UV radiation and copper vapor laser light (578 nm, yellow light) and whether the thermal influence from laser light had a carcinogenic potential itself. Study Design/Materials and Methods: The study was conducted in lightly pigmented hairless hr/hr C3H/Tif mice and included 8 groups of 17-20 mice. Intensities of 0.5, 1.0, and 1.4 W were used, corresponding to calibrated Hexascan fluences of 15.9, 31.8, and 44.6 J/cm(2). Beam diameter was 1 mm and pulse duration 250 msec. UV irradiation of the mice was performed 4 days weekly and started the day after laser treatment. The UV simulated solar ultraviolet radiation came from one Phillips TL 12 and five Bellarium-S SA-1-12 tubes. The daily dose was 1.3 J/cm(2), equivalent to 2.1 B-MED. Results: No tumors appeared in groups receiving laser light only. The time to first (P < 0.01), second (P < 0.01), and third (P < 0.02) tumor was significantly delayed in the group treated with 1.4 W before UV irradiation (P < 0.01) compared with those receiving UV radiation only. No significant differences could be demonstrated for the groups treated with 0.5 and 1.0 W. Conclusion: One laser treatment with the copper vapor laser did not accelerate UV-induced photocarcinogenesis, and the laser exposure did not have a malignant potential itself. (C) 1996 Wiley-Liss, Inc.