To explore the clinical characteristics of immune checkpoint inhibitor-related pneumonitis (CIP) caused by pembrolizumab.

We reported a case of CIP caused by pembrolizumab admitted in Peking Union Medical College Hospital and searched case reports on CIP caused by pembrolizumab in PubMed, Embase, ScienceDirect, CNKI, VIP, and Wanfang databases (as of October 1, 2019). The main clinical data (gender, age, primary diseases, use of pembrolizumab, combination drugs, time to onset of CIP, symptoms, imaging results, CIP grade, and treatment and outcome) in all reported cases were collected and analyzed.

A total of 33 patients were enrolled, including 23 males and 10 females, aged from 44 to 91 years with a median age of 64 years. The primary diseases in 11 cases were melanoma, in 9 cases were lung adenocarcinoma, in 4 cases were lymphoma, in 3 cases were colon cancer, and in 6 patients were esophageal cancer, breast cancer, nasopharyngeal cancer, pulmonary pleomorphic carcinoma, pulmonary large-cell neuroendocrine carcinoma, and lung squamous cell cancer, respectively. Thirty patients received pembrolizumab as monotherapy, 1 patient received combination therapy of pembrolizumab with carboplatin and pemetrexed, and 2 patients received pembrolizumab combined with radiation therapy. Time to onset of CIP in the 33 patients was 1 day at the shortest and 2 years at the longest with a median time of 12(4, 16) weeks. The symptoms of CIP mainly were dyspnea in 19 cases, cough and expectoration in 15 cases, and fever in 9 cases. The common radiological features were ground glass opacities in 17 cases, consolidations in 11 cases, and grid-like high-density shadow in 8 cases. After the diagnosis of CIP, all patients stopped using pembrolizumab. Twenty-nine patients were treated with glucocorticoids, 19 patients received antibacterial therapy, 2 patients received human immunoglobulin, 1 patient received infliximab, and 2 patients did not receive any intervention. Of the 30 patients with known clinical outcomes, 24 patients were improved and 6 died. Among the improved patients, 6 patients underwent rechallenge with pembrolizumab and 1 of them developed CIP again.

The clinical symptoms and radiologic features of CIP caused by pembrolizumab are lack of specificity. Constant vigilance for the presences of fever and respiratory symptoms within 12 weeks after pembrolizumab treatment is required. The CIP in most patients can be improved after drug withdrawal and additional use of glucocorticoids, but the potential fatal risk of CIP is still need to be alert to.

Antineoplastic agents, immunological; Pneumonia; Drug-related side effects and adverse reactions; Pembrolizumab