OBJECTIVES Immune checkpoint inhibitors (ICIs) can cause pneumonitis in lung cancer patients. We aimed to identify the clinical and radiologic characteristics, incidence, and risk factors of ICI-related pneumonitis in patients with non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS Medical records and chest computed tomography scans of NSCLC patients treated with an ICI over a 5-year period at a tertiary hospital were retrospectively analyzed. Clinical characteristics were compared between patients with and without ICI-related pneumonitis to identify risk factors.

RESULTS Data from 167 eligible patients were analyzed. The incidences of all-grade and grade 3-4 pneumonitis were 13.2% and 4.2%, respectively. The presence of preexisting interstitial lung disease [odd ratio (OR), 6.03; 95% confidence interval (CI), 1.19-30.45; P = 0.030] was associated with a higher incidence of ICI-related pneumonitis. The presence of extrathoracic metastasis [OR, 0.34; 95% CI, 0.13-0.92; P = 0.034] was associated with a lower incidence of ICI-related pneumonitis. The dominant radiologic pattern (72.7%) of ICI-related pneumonitis was organizing pneumonia. Half of the patients with pneumonitis completely recovered or improved; however, the mortality rate was 18.2%.

CONCLUSION ICIs should be used with caution when treating lung cancer patients who have underlying chronic lung disease, especially interstitial lung disease.