Immune Checkpoint Inhibitor-Related Pneumonitis in Lung Cancer Patients with Interstitial Lung Disease: Significance of Radiological Pleuroparenchymal Fibroelastosis

Pleuroparenchymal fibroelastosis (PPFE) findings are associated with poor prognosis in interstitial lung disease (ILD). However, the effect of PPFE findings on the development of immune checkpoint inhibitor-related pneumonitis (ICI-pneumonitis), a life-threatening adverse event, in lung cancer patients with ILD has not been elucidated. We aimed to determine whether PPFE findings are a risk factor for ICI-pneumonitis in lung cancer patients with ILD.We retrospectively examined 712 lung cancer patients, including 173 patients with background ILDs, who received ICI therapy in our institute between December 2015 and May 2021. Background ILDs were radiologically classified into three types: lone PPFE, other ILDs with PPFE, and other ILDs without PPFE. The cumulative ICI-pneumonitis incidence curves and median overall survival (mOS) were compared between the three radiological types, and risk factors for ICI-pneumonitis were evaluated.Of 173 eligible patients with ILD, 23 patients (13.3%) experienced ICI-pneumonitis. The Kaplan-Meier method and the log-rank test showed that lone PPFE patients had significantly lower incidence of ICI-pneumonitis (p = 0.024) and longer mOS (575 vs. 326 days; p = 0.0096) than other ILDs patients. ICI-pneumonitis (p = 0.35) and mOS (p = 0.29) were not significantly different between other ILDs with and without PPFE. A multivariate Cox proportional hazards regression analysis revealed that lone PPFE pattern was an independent predictive factor for ICI-pneumonitis (hazard ratio, 0.20; 95% confidence interval, 0.043-0.93; p = 0.040).ICI therapy could be safer in lone PPFE patients than in other ILDs patients with lung cancer.