CD274 and small cell lung carcinoma: Patients with previously treated recurrent/metastatic SCLC and PD-L1-positive expression received pembrolizumab monotherapy and achieved an ORR of 33.3% with median OS of 9.7 months.139 In a phase II, open-label and multi-cohort study (KEYNOTE-158), patients with recurrent/metastatic SCLC receiving pembrolizumab monotherapy had an ORR of 18.7% and an OS of 8.7 months.