Case Report: Serplulimab-induced checkpoint inhibitor pneumonitis in extensive-stage small cell lung cancer with underlying COPD: a case report and literature review.

Background: Serplulimab, a first-line therapy for extensive-stage small cell lung cancer (ES-SCLC), can cause checkpoint inhibitor pneumonitis (CIP). The clinical features and outcomes of serplulimab-induced CIP in patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage IV chronic obstructive pulmonary disease (COPD) remain unclear. Case description: An 80-year-old man with ES-SCLC and preexisting GOLD stage IV COPD received first-line serplulimab plus chemotherapy. After achieving an initial partial response, chemotherapy was discontinued due to reduced tolerance following bacterial pneumonia, and he was continued on serplulimab monotherapy. Three days after the first maintenance dose of serplulimab, he presented with acute severe chest tightness, dyspnea, and hypoxemia and was admitted to the hospital 4 days later. Chest CT revealed new bilateral pulmonary infiltrates. Extensive workup for infection, acute exacerbation of COPD, and tumor progression was negative; the case was ultimately classified as grade 4 serplulimab-induced CIP. He was treated with high-dose methylprednisolone, intravenous immunoglobulin, and empiric anti-infective therapy, with significant clinical improvement. Follow-up CT at 2 months post-discharge showed significant resolution of pulmonary infiltrates. Conclusions: Severe, life-threatening CIP can occur in elderly patients with ES-SCLC and preexisting GOLD stage IV COPD. In this patient, prompt recognition, intensive immunosuppression, and permanent programmed death-1 (PD-1) inhibitor discontinuation contributed to a favorable outcome. Whether preexisting GOLD stage IV COPD confers an increased risk of severe CIP in this understudied population warrants further investigation.