Clinical Outcomes of Anti-programmed Death-1 Antibody–Related Pneumonitis in Patients with Non-Small Cell Lung Cancer

Immune checkpoint inhibitors have provided a breakthrough in cancer therapy. Pneumonitis related to immune checkpoint inhibitors is a serious immune-related adverse event that can be fatal. However, the response to corticosteroids and clinical course of pneumonitis remain poorly understood. We retrospectively reviewed the records of patients who received monotherapy with anti-programmed death 1 (PD-1) antibody, nivolumab, or pembrolizumab, and examined cases with anti-PD-1 antibody-related pneumonitis. The incidence, response to treatment, and recurrence of pneumonitis were investigated. Of 592 patients who received nivolumab or pembrolizumab, 79 developed anti-PD-1 antibody-related pneumonitis. The incidence of all-grade and grade 3–5 pneumonitis was 13.3% and 5.1%, respectively. Despite corticosteroid therapy, 16.5% of pneumonitis cases did not improve, which occurred significantly more frequently in patients with poor performance status, low serum albumin level, and pleural effusion. Among patients with improved pneumonitis, 12.3% experienced recurrence of pneumonitis without re-administration of anti-PD-1 antibody. Anti-PD-1 antibody was re-administered in 16 patients after initial clinical improvement, and five (31.2%) patients experienced a second recurrence of pneumonitis. The incidence of pneumonitis was not rare in real-world settings. Even after improvement of pneumonitis, pneumonitis flare can occur with and without PD-1 antibody re-administration.