Prognosis of Connective Tissue Disease Related Interstitial Lung Disease after Initiation of Long-Term Oxygen Therapy: Comparison with Idiopathic Pulmonary Fibrosis

Objective: The studies of long-term oxygen therapy (LTOT) for patents with connective tissue disease-related interstitial lung disease (CTD-ILD) are limited. This study aimed to evaluate the prognosis of CTD-ILD patients following the initiation of LTOT, compared to those with idiopathic pulmonary fibrosis (IPF). Methods: We conducted a retrospective analysis of patients with CTD-ILD and IPF who were introduced to LTOT between January 2014 and December 2020. Results: The study included 24 patients with CTD-ILD and 55 patients with IPF. At the initiation of LTOT, female gender, never-smoking history, higher body mass index (BMI), higher lactate dehydrogenase (LDH) level, lower pulmonary Surfactant Protein-D (SP-D) level and lower Gender-Age-Physiology (GAP) scores were more common in the CTD-ILD group (all < 0.05). The time from ILD diagnosis to LTOT initiation in CTD-ILD patients was significantly longer than IPF patients (36.0 vs 23.5 months, p = 0.028). Log-rank tests showed that CTD-ILD patients had significantly longer survival compared to IPF patients after the diagnosis of ILD (p < 0.001). However, no significant difference in survival after the initiation of LTOT was noted between patients with CTD-ILD and IPF (p = 0.276). Conclusion: Although patients with CTD-ILD had longer overall survival than those with IPF, there was no significant difference in prognosis after the initiation of LTOT between the two groups. Early intervention including treatment and management will be needed in CTD-ILD as in IPF.