Prognosis of connective tissue disease related interstitial lung disease after initiation of long-term oxygen therapy: comparison with idiopathic pulmonary fibrosis

Background 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 investigate the prognosis of patients with CTD-ILD after the initiation of LTOT, compared to those with idiopathic pulmonary fibrosis (IPF). Methods We retrospectively investigated 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. 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 interstitial lung disease (ILD) diagnosis to LTOT initiation for patients with CTD-ILD was significantly longer than for patients with IPF (36.0 vs 23.5 months, p = 0.028). Log-rank tests showed that patients with CTD-ILD 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.