ALK and non-small cell lung carcinoma: Pembrolizumab (a PD-1 inhibitor) is the first immunotherapy that was approved by the FDA for the treatment of patients with metastatic NSCLC, whose tumors express PD-L1 and requires confirmation of PD-L1 overexpression [16,50,51] (defined as expression in at least 50% of tumor cells), and no activating mutations of EGFR or ALK rearrangements in NSCLC patients with either squamous or nonsquamous histology.