Biomarkers of fibrotic interstitial pneumonia with antifibrotic agent treatment

<bold>Background:</bold> Thymus and activation-regulated chemokine (TARC)/CC chemokine ligand 17 levels were elevated in patients with fibrotic hypersensitivity pneumonitis and dermatomyositis, suggesting its potential as an indicator of fibrotic interstitial pneumonia. <bold>Objective:</bold> This study aimed to examine the utility of blood TARC levels in predicting the prognosis of interstitial pneumonia in the context of antifibrotic agent treatment. <bold>Methods:</bold> Clinical data from patients diagnosed with interstitial pneumonia and initiated on antifibrotic agents were retrospectively analyzed at our hospital between April 23, 2009 and May 11, 2022. The relation between blood TARC concentration and survival after antifibrotic initiation (commencing with either pirfenidone or nintedanib) was analyzed. Additionally, clinically relevant cutoff values were evaluated and discussed. <bold>Results:</bold> Of the 136 patients diagnosed with interstitial pneumonia during the specified period, 52 individuals with analyzable blood TARC levels were included. The median age was 75 years (36–91) with 46 males. Logistic regression analysis revealed a significant association between mortality and blood TARC levels 3 years after antifibrotic initiation (p = 0.0312). The TARC cutoff value indicated by the ROC curve was 603 pg/mL. The high-level group (22 patients) and the low-level group (30 patients) showed significant differences (p = 0.0004 and 0.0010) according to the log-rank and generalized Wilcoxon tests. <bold>Conclusion:</bold> Blood TARC levels are a potential prognostic factor in patients undergoing antifibrotic treatment, indicating their utility in predicting outcomes.