Narrow-band UV-B (TL-01) Phototherapy Exposure and Skin Cancer Risk: A Nested Case-control Study

Narrow-band TL-01 ultraviolet B phototherapy (TL-01) is generally considered a relatively safe treatment for skin diseases, although conflicting findings have also been reported. This study aimed to evaluate the association between TL-01 exposure and skin cancer risk using a nested case-control design within a Finnish cohort of 4,815 patients treated with TL-01 monotherapy, with subsequent 38 cases of basal cell carcinoma, 13 cases of cutaneous melanoma, and 9 cases of cutaneous squamous cell carcinoma. Four matched controls were selected for each skin cancer case. Personal TL-01 exposure data were obtained from hospital records. Conditional logistic regression was used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs). An increased risk for basal cell carcinoma was observed with higher TL-01 exposure (OR per 20 sessions 1.36, 95% CI 1.08-1.72), whereas no association was found for cutaneous melanoma or cutaneous squamous cell carcinoma. In a categorical analysis, with category of 1-29 TL-01 sessions as the reference, the risk of basal cell carcinoma was markedly elevated among patients who received ≥60 sessions (OR 4.16, 95% CI 1.49-11.6). Occupational outdoor work was considered a potential confounder, but it had no effect. Further studies with larger cohorts and longer follow-up are needed to confirm these findings.