Frequency of skin cancer among psoriasis, vitiligo, and mycosis fungoides patients treated with narrowband ultraviolet B phototherapy

Background: Narrowband ultraviolet B (NB-UVB) phototherapy is a popular and relatively contemporary treatment option. However, only a few studies to date have explored the potential risk of skin cancer following NB-UVB treatment. Objective: This study aimed to investigate the potential long-term risk of skin cancer in patients treated with NB-UVB. Methods: This cohort study included patients with psoriasis, vitiligo, and mycosis fungoides treated with NB-UVB at two university hospitals in Israel in 2000–2005. Patients were followed up for skin cancer for at least 10 years. Data were extracted from the hospital and community medical records. Results: A total of 767 patients were included in this study: 509 with psoriasis, 122 with vitiligo, and 136 with mycosis fungoides. The mean follow-up duration was 13 years. Among these patients, 4.43% developed skin cancer during the follow-up (3.93% had psoriasis, 2.46% had vitiligo, and 8.09% had mycosis fungoides). Old age and fair skin type were the only significant independent risk factors for skin cancer. There was no significant difference in the mean number of NB-UVB treatments among patients who developed skin cancer and those who did not (99.09 vs. 94.79, respectively). Conclusion: No association was observed between the number of NB-UVB treatments and carcinogenesis in any study group. Age is a significant risk factor, and older patients treated with NB-UVB should be followed up carefully.