ALK and non-small cell lung carcinoma: Pembrolizumab monotherapy was approved in January 2017 for the first-line treatment of patients with metastatic NSCLC whose tumors have high PD-L1 expression (≥ 50%) and no EGFR or ALK positive tumor mutations [17, 22], and pembrolizumab in combination with chemotherapy was approved in September 2018 and March 2019 for patients with NSQ and SQ NSCLC, respectively [23, 24].