Methotrexate did not add skin cancer risk in patients with psoriasis receiving narrow-band ultraviolet B phototherapy: a nationwide retrospective cohort study.

BACKGROUND: In the era of biologic therapy, phototherapy and methotrexate (MTX) are still commonly employed for patients with moderate-to-severe psoriasis. However, the skin cancer risk following a combination of MTX and narrow-band ultraviolet B (NB-UVB) has rarely been explored.

OBJECTIVES: To investigate whether MTX plus NB-UVB increases skin cancer risk in patients with psoriasis.

METHODS: We conducted a retrospective cohort study of data in Taiwan National Health Insurance Research Database from 1997 to 2013. We performed cumulative incidences and multivariate analysis using competing risk regression model, comparing skin cancer risk between cohorts of combination therapy and using NB-UVB alone, matched by relative confounders. We further conducted sensitivity analysis for those receiving higher MTX dosage. Standardized incidence ratio (SIR) was calculated for skin cancer risk.

RESULTS: We enrolled 3203 subjects in each cohort. No significant differences in skin cancers were noted between the two cohorts in the cumulative incidences (log-rank test, p = 0.282) and hazard ratio (HR) (adjusted HR = 0.50, 95% CI 0.15, 1.63, p= 0.247) on the competing risk regression model. There were also no significant differences between those receiving higher dose MTX and UVB alone in the cumulative incidences of skin cancers (p = 0.227) and HR (adjusted HR = 0.29, 95% CI 0.04, 2.21, p = 0.231) in the multivariate analysis. There was no significant difference of SIR between the two cohorts compared to the general population.

CONCLUSIONS: MTX does not increase skin cancer risk in patients with moderate-to-severe psoriasis receiving NB-UVB in the Taiwanese population.