A Study of Concurrent Chemoradiation With Atezolizumab in Participants With Untreated Extensive-Stage (ES) Small Cell Lung Cancer (SCLC)

Etoposide-cisplatin/ -carboplatin in combination with PD-L1 inhibitor for 4 cycles followed by maintenance therapy with PD-L1 inhibitor is currently the world-wide first-line treatment for extensive-stage small cell lung cancer. When 4 cycles of EC/EP chemotherapy combined with PD-L1 inhibitor are effective, guidelines recommend additional thoracic radiotherapy. In our study, the investigators bring radiotherapy forward, which means that after 2 cycles of EC/EP chemotherapy plus Atezolizumab, participants with response（PR/CR/SD）will receive concurrent radiotherapy and 2 cycles of EC/EP chemotherapy plus Atezolizumab, then maintenance therapy with Atezolizumab （Q3W）. The purpose of this study is to explore the safety and efficacy of Atezolizumab combined with concurrent chemoradiotherapy in untreated participants with extensive-stage small cell lung cancer.