High mortality and poor treatment efficacy of immune checkpoint inhibitors in patients with severe grade checkpoint inhibitor pneumonitis in non‐small cell lung cancer

BACKGROUND: The treatment efficacy of immune checkpoint inhibitor (ICI) and clinical outcomes in patients with non‐small cell lung cancer (NSCLC) who develop severe grade checkpoint inhibitor pneumonitis (CIP) are unclear. Here, we report on the treatment efficacy of ICI and prognosis in NSCLC patients with severe grade CIP. METHODS: In this retrospective cohort study, CIP severity, CIP‐related mortality, and ICI efficacy in 71 patients with advanced NSCLC treated with ICIs were evaluated. Data was obtained from the patients’ medical charts. RESULTS: All grade and severe grade CIP were observed in 22 and 11 patients, respectively. The CIP‐related mortality rate was 22.7% (N = 5). An Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) score of ≥2 and pre‐existing interstitial lung disease (ILD) were significantly associated with the development of severe grade CIP (P = 0.001 and P = 0.035, respectively). The median progression‐free survival (PFS) and overall survival (OS) were significantly shorter in patients with severe grade CIP than in those without severe grade CIP (PFS 1.0 month, 95% confidence interval [CI] 0.5–2.0 vs. 3.5 months, 95% CI 2.0–5.0 months, P = 0.003; OS 3.0 months, 95% CI 0.5–13 vs. 12.7 months, 95% CI 8.0–21.0 months, P = 0.011). CONCLUSION: CIP is a serious complication with a poor prognosis associated with high mortality. The efficacy of ICI is significantly worse in patients with severe grade CIP than in those without severe grade CIP. Whether ICIs should be administered to patients with CIP risk factors, such as an ECOG PS score of ≥2 or pre‐existing ILD, should be carefully assessed.