Which biologic in rheumatoid arthritis with progressive lung fibrosis

Design

retrospective real-world comparative cohort with propensity-score-based inverse probability of treatment weighting

Population

135 patients with rheumatoid arthritis-associated progressive pulmonary fibrosis (TNF inhibitor 35, abatacept 45, IL-6 receptor inhibitor 55), drawn from 2,484 starting a biologic

Primary outcome

change in pulmonary function and visual CT score at week 52

Effect

lung function and CT scores stable overall; FVC +3.3% on IL-6 receptor inhibition versus -3.2% on TNF inhibition (p = 0.011, Cohen's d 0.63); fewest adverse events on abatacept

Of 2,484 patients with rheumatoid arthritis starting a biologic, 443 had interstitial lung disease and 135 met criteria for progressive pulmonary fibrosis. Those 135 — 35 on a TNF inhibitor, 45 on abatacept, 55 on an interleukin-6 receptor inhibitor — were followed for 52 weeks with lung function, visual CT scores and disease activity, compared using propensity-score-based inverse probability of treatment weighting.

The first finding is the reassuring one: on any of the three, joint disease improved substantially and lung function and CT scores stayed broadly stable over the year. Adjusted comparisons found no difference between classes in disease activity, CT score or drug retention. Forced vital capacity did differ, improving on interleukin-6 receptor inhibition and falling on TNF inhibition (+3.3% versus -3.2%, p = 0.011). Adverse events were less frequent on abatacept. Interleukin-6 receptor inhibition, a non-UIP pattern and lower disease activity at week 52 independently predicted FVC improvement.

With 35 to 55 patients per arm and treatment chosen by clinicians who knew the CT pattern, this cannot establish that one class protects the lung. The message that does survive is the one in the conclusion: controlling the joint disease tightly is associated with lung stability, and the finding that lower disease activity at 52 weeks predicted FVC improvement is the most actionable part of the paper. Where the pattern is non-UIP and a choice exists, an interleukin-6 receptor inhibitor is a defensible preference; where safety dominates, abatacept had the fewest events.

• Record the CT pattern — UIP versus non-UIP predicted who improved
• Repeat spirometry at 52 weeks rather than relying on symptoms to detect progression
• Treat the joints to target: lower disease activity at a year was linked to better FVC
• TNF inhibitors are not contraindicated here, but this cohort favoured other classes on lung outcomes
• Discuss the choice with the respiratory team where antifibrotic therapy is also being considered

The statistics, in plain English

A difference of 6.5 percentage points in FVC change between classes with a Cohen's d of 0.63 is a moderate effect, but it comes from arms of 35 and 55 patients, so the confidence interval around it is wide and a single outlying patient moves it. Propensity weighting balances the factors that were measured — it cannot balance the clinician's impression of how aggressive the lung disease looked, which is precisely what drove the prescribing decision. The predictors of FVC improvement come from a multivariable model in 135 patients, which is too few for the number of variables tested to be treated as confirmed.

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