New Australian research spanning three decades provides “conclusive” evidence linking methotrexate with an increased risk of non-melanoma skin cancer.

The role of methotrexate and anti-TNFS used to treat RA in elevated skin cancer risk have been the subject of much debate, but the large study published in Rheumatology should put the speculation to rest, said co-author, Professor Graeme Jones.

“I think it’s pretty conclusive,” he told the limbic. “I’m pretty sure that methotrexate’s the culprit.”

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Professor Jones, Head of the Musculoskeletal Research Group at the Menzies Institute for Medical Research, University of Tasmania, and fellow researchers collected medication information on 405 patients with RA or PsA in two private rheumatology practices and was matched to comprehensive histologically confirmed cancer registry data for the years 1978–2005.

And it’s the decades of data that give this verdict its teeth.

“Methotrexate and concurrent methotrexate Ciclosporin-A and D-penicillamine use is associated with an increased risk of NMSC,” the authors wrote. “These results should encourage greater clinical vigilance for NMSC in treated patients with RA and PsA.”

Professor Jones agreed, and said it was important to point out that NMSC was the only cancer that seems to be “more common with methotrexate.”

“I think it reinforces the need to be more careful if you’re on methotrexate, in relation to sun exposure,” he said.

Interestingly, he said he believed the link – while speculation has been around for a while – is not widely appreciated. In fact he said he and his co-authors had found it difficult getting their study published.

But he cautioned against panicking or abandoning methotrexate, which remains an effective treatment and co-treatment for RA. This should continue he said, although patients already at risk of skin cancer might benefit from alternative medication, if it is effective.

“Methotrexate is still a cornerstone drug for RA, and that shouldn’t change,” he said. “What it does mean is patients need to be more vigilant.

He recommends annual visits to a skin cancer clinic or GP for skin checks. It was also something for specialists to put on their radar to follow up with patients.

“It’s pretty easy to just go and have an annual check,” he said.