The application of bronchoscopy in the assessment of immune checkpoint inhibitor-related pneumonitis severity and recurrence

Abstract Purpose: To explore the role of bronchoscopy for the assessment of checkpoint inhibitor pneumonitis (CIP). Method： A retrospective single-center study was conducted to assess patients diagnosed with CIP at grade 2 or above and also underwent bronchoscopy between January 2020 and December 2022. Clinical data and bronchoscopic findings were recorded. The treatment data and prognosis information were collected. Results: Twenty-one patients who underwent bronchoscopy and were diagnosed with CIP were enrolled in this study. All patients underwent bronchoalveolar lavage fluid (BALF) analysis. Of them, T lymphocyte subsets of BALF were tested in 15 cases. Transbronchial cryobiopsywas performed in 8 patients, and transbronchial lung biopsy was performed in 5 patients. 14 patients experienced grade 2 CIP, while 7 patients ≥ grade 3 CIP. Symptoms were improved in 19 (90.5%) patients after standard treatment adhering to CIP guidelines. However, 5 patients relapsed during steroid tapering. Factors related to the severity and recurrence of CIP were analyzed. Patients with previous interstitial lung disease (ILD) were more likely to develop high grade CIP than those without [83.3% (5/6) versus 15.4% (3/15), P=0.011].The odds ratio (OR) was 32.5 (95%CI 2.284-443.145, P=0.009). Increased BALF lymphocyte percentage was associated with high grade CIP, OR 1.095 (95%CI 1.001-1.197, P=0.047), and higher possibility of CIP relapse, OR 1.123 (95%CI, 1.005-1.225, P=0.040). Lymphocyte subsets were tested in 15 patients. CD4/CD8 >1 was found in 80%(4/5) of relapsed patients and 20%(2/10) of patients without relapse (P=0.047). The OR was 16.00 (95%CI 1.093-234.24, P=0.043). Conclusion： In this retrospective study, patients with previous ILD was more likely to develop high grade CIP. Higher lymphocyte percentage in BALF was associated with high grade CIP and susceptibility to relapse during treatment of CIP. A CD4/CD8 ratio greater than 1 in lymphocyte subsets of BALF was associated with higher possibility of CIP relapse.