Immune-related organizing pneumonitis in non-small cell lung cancer receiving PD-1 inhibitor treatment: A case report and literature review

Immune checkpoint blockade with programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) inhibitors has been standard care for metastatic nonsmall cell lung cancer (NSCLC) and after progression using first-line platinum-containing chemotherapy. Although several management guidelines exist for immune checkpoint inhibitor-induced toxicities, uncommon, complicated, and life-threatening immune-related adverse events remain challenging for oncologists. In this report, we presented a male patient with NSCLC who received pembrolizumab during disease progression. He developed interstitial pembrolizumab-induced organizing pneumonia (OP). The patient received 9 months of anti-PD-1 pembrolizumab when he presented with dry cough and fatigue. The patient developed a solitary nodular lung lesion mimicking a newly occurred metastatic lesion in the lung without a significant circulating tumor marker increase. Sputum analysis was negative for acid-fast bacilli and fungi. A computed tomography-guided percutaneous lung biopsy was conducted and showed alveolar fibrous thickness and various lymphocyte infiltration. Immunotherapy-related OP was identified, and he subsequently responded well to corticosteroids. This case describes a clinical situation, where PD-1-induced OP is radiologically similar to NSCLC disease progression in the lungs. Oncologists should be aware of uncommon pulmonary PD-1/PD-L1 inhibitor toxicity. Lung biopsy may help to distinguish immune-related pneumonitis, lung infections, and progressive nodular lesions.