In the phase II KEYNOTE-021 open-label trial, 123 patients with stage IIIB or IV NSCLC who did not demonstrate targetable EGFR mutations or ALK translocations received either pembrolizumab 200 mg plus pemetrexed 500 mg/m2 and carboplatin area under the curve (AUC) 5 mg/mL/min every 3 weeks for 4 cycles follow by pembrolizumab 200 mg for 24 months and indefinite pemetrexed maintenance therapy, or pemetrexed 500 mg/m2 and carboplatin AUC 5 mg/mL/min followed by indefinite pemetrexed maintenance therapy alone. Here, ALK is linked to non-small cell lung carcinoma.