Clinical Features and Determinants of Disease Severity of Immune Checkpoint Inhibitor-Related Pneumonitis: A Retrospective Study

Background Immune checkpoint inhibitor associated pneumonia(CIP) is the most dangerous adverse reaction of immunecheckpoint inhibitors. Howerer,research on the factors affecting its severity is limited. Methods This retrospective study analyzed 2673 patients who underwent immune checkpoint inhibitor(ICI)treatment at the First Affiliated Hospital of Zhejiang University between 2019 and 2023. Of these, 106 cases of i mmune checkpoint inhibitor associated pneumonia(CIP) were identified, all of which were associated with lung cancer. The clinical manifestations and diagnostic and therapeutic approaches used for these 106 patients were summarized. The patients were also classified into four types based on clinical characteristics and imaging findings, and a detailed analysis was conducted. Results It was found that i mmune checkpoint inhibitor associated pneumonia(CIP) occurred at a median of 5.17 months (95%CI 4.61‒5.72) after the start of immune checkpoint inhibitor(ICI) therapy.Grade 4 was usually the earliest to be identified and had the poorest prognosis, with a median onset of 2.47 months after treatment (95%CI 0, 5.12 months), an incidence rate of 4.7%, a median progression-free survival (mPFS) of 3.83 months, and a median overall survival (mOS) of 4.03 months. The PFS curves for Grades 1–2 and Grades 3–4 CIP showed separation but without statistical significance (mPFS 8.47 m vs. 6.50 m, HR = 3.36, log-rank P = 0.07), while the difference in OS was significant OS (mOS 23.15 m vs. 11.20 m, HR = 8.97, log-rank P = 0.003). Multivariate logistic regression showed that forced vital capacity (FVC) was the only predictive factor linked to 3–4 grades occurrence (OR = 1.00, 95% CI 0.01–0.80, P = 0.03), with decreased forced vital capacity (FVC) an independent risk factor for the grade 3–4 CIP (OR = 1.00, 95% CI 0.01–0.80, P = 0.03). Conclusions Forced vital capacity(FVC) was observed to be the only independent risk factor for grade 3–4 i mmune checkpoint inhibitor associated pneumonia( CIP), reminding us of the importance of assessing baseline pulmonary function testing before immune checkpoint inhibitor use. In addition to forced vital capacity(FVC), active monitoring of radiological examinations and clinical manifestations remains meaningful.