Methotrexate Use for Patients with Psoriasis and Risk of Cutaneous Squamous Cell Carcinoma: A Nested Case-control Study

An association between methotrexate use and risk of cutaneous squamous cell carcinoma has been reported in patients with rheumatoid and psoriatic arthritis. A nested case-control study was performed to investigate if methotrexate use among patients with psoriasis was associated with increased risk of cutaneous squamous cell carcinoma. Data were obtained from Swedish registers and included 623 patients with psoriasis and a first cutaneous squamous cell carcinoma from 2010 to 2016. Ten randomly selected patients with psoriasis were matched on age and sex to each case. Among cases, 160 (26%) were ever-users of methotrexate. The corresponding number among the controls was 1,370 (22%), yielding an unadjusted odds ratio (OR) of 1.23 (95% confidence interval (95% CI) 1.02–1.49); p = 0.034. After adjusting for use of other immuno-suppressive drugs the association was close to unity (OR 1.09; 95% CI 0.89–1.34); p = 0.39. The slightly increased risk of cutaneous squamous cell carcinoma associated with methotrexate-exposure in patients with psoriasis does not seem to be associated with methotrexate, but rather with disease severity, other antipsoriatic treatments, and ultraviolet exposure.