Immune checkpoint inhibitor-related pneumonitis following discontinuation of pembrolizumab in a patient with advanced lung adenocarcinoma: a case report and literature review.

BACKGROUND

Checkpoint inhibitor-related pneumonitis (CIP) is a rare but serious complication of immune checkpoint inhibitors (ICIs). While it typically occurs within the first few months of treatment, its onset after ICI discontinuation is relatively uncommon. This report presents a case of CIP occurring 2.5 months after cessation of pembrolizumab and reviews the existing literature on CIP after discontinuation of ICIs.

CASE PRESENTATION

A 77-year-old female with stage IV right lung adenocarcinoma (T4N2M1a) developed pneumonitis 2.5 months after discontinuation of pembrolizumab (following 26 months of initial treatment). Initially suspected as community-acquired pneumonia, the patient received antiviral and antibiotic therapy with progressive deterioration. Microbiological investigations yielded negative results, and consultation suggested lung cancer recurrence. PET-CT revealed heightened metabolic activity in the lungs. Percutaneous lung biopsy demonstrated organizing pneumonia, and NGS testing of biopsy tissue showed no pathogenic organisms. Combined with CT findings and the patient's history of pembrolizumab use, the diagnosis of checkpoint inhibitor-related pneumonitis (CIP) was established. Short-term steroid therapy resulted in significant improvement.

CONCLUSIONS

Integration of clinical presentation, imaging findings, and medication history is crucial for diagnosis. This case underscores the need for vigilance for CIP even after discontinuing ICI therapy. Although this report provides insights into CIP after discontinuation based on a single case and a literature review, further studies involving larger cohorts are warranted to better understand the post-treatment risk of CIP.