Risk of skin cancer in psoriasis patients receiving long‐term narrowband ultraviolet phototherapy: Results from a Taiwanese population‐based cohort study

Background Narrowband ultraviolet B (NB-UVB) phototherapy is a widely used treatment for various dermatoses. The risk of skin cancer following long-term NB-UVB phototherapy has rarely been explored in skin phototypes III-V. Methods We conducted a nationwide-matched cohort study and identified a total of 22 891 psoriasis patients starting NB-UVB phototherapy from the Taiwan National Health Insurance Database during the period 2000-2013. Cumulative incidences of skin cancers were compared between subjects receiving less than 90 UVB treatments (S-cohort, N = 13 260) and age- as well as propensity score-matched subjects receiving more than or equal to 90 UVB treatments (L-cohort, N = 3315). Results There were no significant differences in the overall cumulative incidences of skin cancers between the two cohorts (log-rank t test, P = 0.691) during the follow-up periods. The S-cohort had a significantly lower prevalence of actinic keratosis when compared with the L-cohort (0.54% vs 1.00%, P = 0.005). Conclusion Long-term NB-UVB phototherapy does not increase skin cancer risk compared with short-term NB-UVB phototherapy in psoriasis patients with skin phototypes III-V.