Clinical implications of bronchoscopy for immune checkpoint inhibitor-related pneumonitis in patients with non-small cell lung cancer

Background The utility of bronchoscopy for patients with suspected immune checkpoint inhibitor (ICI)-related pneumonitis is currently debatable. The purpose of this study was to examine the findings of bronchoalveolar lavage (BAL) analysis and transbronchial lung biopsy (TBLB) in non-small cell lung cancer (NSCLC) patients with ICI-related pneumonitis, and to elucidate the clinical significance of bronchoscopy for this health condition. Patients and methods Consecutive NSCLC patients treated with ICIs, diagnosed with ICI-related pneumonitis after undergoing bronchoscopy between October 2015 and March 2019 were retrospectively screened. Findings of BAL fluid analysis and/or TBLB specimen histology were reviewed. Results Twelve patients underwent bronchoscopy for the diagnosis of ICI-related pneumonitis, ten of whom underwent BAL. An increase in the proportion of lymphocytes higher than 20% was observed in all ten patients. An increase in the proportion of neutrophils (> 10%) and eosinophils (> 10%) was observed in two and one patient, respectively. TBLB specimens were analyzed for eight patients. Major histologic findings included alveolitis in seven (87.5%) and organizing pneumonia (OP) in five (62.5%) patients. Other findings included acute lung injury and fibrosis. All twelve patients demonstrated favorable outcomes. Conclusion A major characteristic of BAL analysis in ICI-related pneumonitis with NSCLC was an increased proportion of lymphocytes. The histologic features of lung tissue included alveolitis and/or OP. Acute lung injury and fibrosis were observed. Although the necessity of bronchoscopy should be determined on a case-by-case basis, it is necessary to assess these parameters when proper differential diagnosis is needed.