How common is methotrexate pneumonitis? A large prospective study investigates

Abstract

The current literature states the prevalence of methotrexate pneumonitis (MTX-P) to be 3.5-7.6%. This is based on retrospective data. Consequently, clinicians remain cautious in using methotrexate especially in patients with pre-existing lung disease. To get a true idea of the incidence of MTX-P we designed an ongoing prospective study, which is the largest to date. We recruited all patients starting low-dose methotrexate in our department, and followed them up for 2 years or until development of MTX-P. All patients had their pulmonary spirometry checked at baseline. Patients were excluded if they did not give consent for methotrexate therapy, or had a forced expiratory volume in 1 s (fev1) or full vital capacity (FVC) of less than 1 l. So far, 223 patients have been recruited of whom 223 have completed 6 months and 185 have finished 2 years of follow-up from commencing methotrexate. Only two patients developed MTX-P. This gave an incidence of one case every 192 patient years of MTX-P. The results of this ongoing prospective study suggest that MTX-P when diagnosed using Carson's criteria and Chest HRCT scanning, does not occur as often as previously thought. Also it would appear from our data that baseline spirometry rather than full pulmonary function tests can be used routinely as an immediate screening of lung function prior to commencement of methotrexate. Interestingly the patients who developed MTX-P did not have any specific abnormalities at baseline.

High-resolution CT and pulmonary function tests in rheumatoid arthritis patients with subclinical interstitial lung disease in Kuwait

“…Interestingly, in patients with pulmonary fibrosis, MTX did not cause any deterioration in pulmonary function over a 2-yr period. In another study of Sathi et al [30], MTX has not been shown to accelerate the progression of underlying ILD in RA [15].…”

Methotrexate induced pneumonitis

“…16 In a recent study (2012) Sathi et al reported an incidence of one case every 192 patient years. 17 The same group in 2008 had reported a prevalence of 1%(2/211). According to them MTX-P is rare.…”

“…25 Sathi et al (2012) suggest that baseline spirometry rather than full pulmonary function tests can be used routinely, prior to starting MTX. However in their study they did not find any specific base-line abnormalities in patients who developed MTX-P. 17 The role of preexisting lung disease on the development of MTX-pulmonary toxicity has been debated. Golden et al (1995) studied 93 women and 32 men with RA treated with MTX.…”

“…HRCT with its better sensitivity is becoming the imaging modality of choice. 17 There are bilateral patchy ground glass opacities, distributed throughout the lungs. Presence of centrilobular opacities suggests the possibility of MTX-P. Honey-combing is not a feature.…”

“…According to Sathi et al, rather than full PFTs, spirometry can be employed for pre-screening. 17 Evidence-based guidelines have been developed for the use of methotrexate in rheumatic disorders by Visser et al 37 Implementation of these recommendations in clinical practice largely helps to prevent and/or monitor the patients on MTX.…”