CD274 and small cell lung carcinoma: In IMpower133, investigators assessed the safety and efficacy of the addition of atezolizumab, an inhibitor of PD-L1, versus placebo to first-line carboplatin and etoposide in four 21-day cycles, followed by a maintenance of atezolizumab versus placebo based on the initial randomization, in a 1:1 double-blind randomization of 403 treatment-naive ES-SCLC.