[Clinical and chest CT features of immune checkpoint inhibitor-related pneumonitis]

Objective: To explore the clinical and chest computed tomography (CT) features and the outcome of immune checkpoint inhibitor-related pneumonitis (CIP). Methods: Clinical and chest CT data of 38 CIP patients with malignant tumors from the Cancer Hospital, Chinese Academy of Medical Sciences between August 2017 and April 2021 were retrospectively reviewed, and the outcomes of pneumonitis were followed up. Results: The median time from the administration of immune checkpoint inhibitors (ICIs) to the onset of CIP was 72.5 days in 38 patients with CIP, and 22 patients developed CIP within 3 months after the administration of ICIs. The median occurrence time of CIP in 24 lung cancer patients was 54.5 days, earlier than 119.0 days of non-lung cancer patients (P=0.138), with no significant statistical difference. 34 patients (89.5%) were accompanied by symptoms when CIP occurred. The common clinical symptoms were cough (29 cases) and dyspnea (27 cases). The distribution of CIP on chest CT was asymmetric in 31 cases and symmetrical in 7 cases. Among the 24 lung cancer patients, inflammation was mainly distributed ipsilateral to the primary lung cancer site in 16 cases and diffusely distributed throughout the lung in 8 cases. Ground glass opacities (37 cases) and consolidation (30 cases) were the common imaging manifestations, and organizing pneumonia (OP) pattern (15 cases) was the most common pattern. In 30 CIP patients who were followed up for longer than one month, 17 cases had complete absorption (complete absorption group), and 13 cases had partial absorption or kept stable (incomplete absorption group). The median occurrence time of CIP in the complete absorption group was 55 days, shorter than 128 days of the incomplete absorption group (P=0.022). Compared with the incomplete absorption group, there were less consolidation(P=0.010) and CIP were all classified as hypersensitivity pneumonitis (HP) pattern (P=0.004) in the complete absorption group. Conclusions: CIP often occurs within 3 months after ICIs treatment, and the clinical and CT findings are lack of specificity. Radiologic features may have a profound value in predicting the outcome of CIP.