Carcinogenic effects of prolonged daily low-emission phototherapy in psoriasis

Background: Low-dose UV treatment has been shown to be effective in mild psoriasis. However, the prolonged use of this treatment modality may raise concerns about its safety. These concerns are mainly focused on potential carcinogenic risks and overuse of this treatment modality. Objectives: This study was set out to evaluate possible carcinogenic risks of prolonged low-dose phototherapy. Methods: Three groups of psoriasis patients were evaluated: patients with local treatment only (n = 15); low-dose UV treatment at home for at least 18 months (n = 39); and patients with conventional NB-UVB (n = 8). Patients underwent visual inspection for signs of photoageing, and p53, CPDs and γH2AX were measured in skin biopsies. Patients undergoing low-dose phototherapy answered a survey about their recent patterns of use in a survey. Results: In the skin biopsies, low-dose UV treatment caused a lower amount of CPDs (p =.016) and p53 (p =.015) than NB-UVB. γH2AX did not show a significant difference. Self-report in patients undergoing low-dose phototherapy showed only one case of overuse (2.7%). Visual skin inspection showed no difference in signs of photoageing in the three groups. Conclusion: Prolonged treatment with low-dose UV for 18 months appears at least as safe as a course of conventional NB-UVB.