Study generates hypothesis but leaves incidence unknown
MAUI, HAWAII – The incidence of methotrexate pneumonitis has been reported as ranging from 3.5% to 7.6% among patients taking the disease-modifying antirheumatic drug. It’s an estimate that Aryeh Fischer, MD, counters with a one-word response: “Nonsense!”
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Dr. Aryeh Fischer
“There’s just no way that methotrexate is causing that much lung disease,” he declared at the 2019 Rheumatology Winter Clinical Symposium.
Dr. Fischer, a rheumatologist with joint appointments to the divisions of rheumatology and pulmonary sciences and critical care medicine at the University of Colorado at Denver, Aurora, noted that his opinion is considered controversial in the pulmonology world.
“I’m not allowed to talk about methotrexate at lung conferences. They stop you at the gate. They’re convinced in lung circles that methotrexate is the worst drug known to mankind,” he said.
“My take home on methotrexate lung toxicity is this: I would just say, yes, it can occur, but it’s super rare and most often we’re not really sure that it was methotrexate pneumonitis. The diagnosis is not definitive, it’s exclusionary. We know that patients with interstitial lung disease of all types get acute exacerbations, and in idiopathic pulmonary fibrosis it’s actually the leading cause of mortality,” the rheumatologist said.
He highlighted a meta-analysis of 22 randomized, double-blind clinical trials published in 1990-2013 of methotrexate versus placebo or active comparators in 8,584 RA patients. The Irish investigators of that meta-analysis found that methotrexate was associated with a small albeit statistically significant 10% increase in the risk of all adverse respiratory events and an 11% increase in the risk of respiratory infection. However, patients on methotrexate were not at increased risk of mortality because of lung disease. And not a single case of methotrexate pneumonitis was reported after 2002 (Arthritis Rheumatol. 2014 Apr;66[4]:803-12).
Methotrexate pneumonitis is not dose dependent, nor is it related to treatment duration.
“Just because your patient has been on methotrexate for years does not mean they won’t get methotrexate lung toxicity,” he cautioned. “But this is not a chronic fibrotic interstitial lung disease, this is an acute onset of peripheral infiltrates and ground glass opacifications on chest imaging.”
Bronchoalveolar lavage classically shows a hypersensitivity pneumonitis with lymphocytosis. Transbronchial or surgical lung biopsy may show an organizing pneumonia or airway-based nonnecrotizing granulomas, again indicative of a hypersensitivity reaction.
Because the diagnostic picture is so often cloudy, Dr. Fischer generally tries to avoid methotrexate in patients with moderate or severe interstitial lung disease. “I have the luxury of avoiding it because we have so many great arthritis drugs these days,” he noted.
“That being said, the notion that we’re going to stop methotrexate in an 80-year-old who’s been on it for years and has mild bibasilar fibrotic interstitial lung disease so that her lung doc can sleep better at night is not very helpful for our patients. If the patient is doing well on methotrexate and the interstitial lung disease is mild, I continue [the methotrexate],” Dr. Fischer said.
He reported receiving research grants from Boehringer Ingelheim and Corbus Pharmaceuticals and serving as a consultant to Boehringer Ingelheim and other pharmaceutical companies.