Does Methotrexate Use Confer Risk for Developing Melanoma?

Some small or poorly controlled studies have suggested a possible association of methotrexate with excess risk for developing melanoma. In this meta-analysis, researchers identified 6 randomized trials and 6 observational studies with data on low-dose methotrexate exposure (5–30 mg/week) and melanoma outcomes; the 17,000 melanoma cases were nearly all from large cohort and case-control studies. In 10 studies, follow-up was at least 2 years.

The combined data resulted in a barely significant excess risk for melanoma (relative risk, 1.15). When one study that accounted for >3000 melanoma cases was removed, the RR became insignificant (1.11). Based on melanoma incidence rates for Australia (a high melanoma-risk country) and North America, the n…