Atezolizumab and Rechallenge Chemotherapy in Relapsed Patients With Extensive-stage Small Cell Lung Cancer (ES-SCLC).

This study is testing whether adding the immunotherapy drug atezolizumab to a second round of platinum-based chemotherapy (the same type used initially) can help people with extensive-stage small cell lung cancer (SCLC) whose cancer has returned after a period of at least 60 days following initial treatment. **You may be eligible if...** - You are 18 or older and have been diagnosed with small cell lung cancer (confirmed by biopsy) - Your cancer progressed or came back at least 60 days after finishing your first round of platinum-etoposide chemotherapy plus immunotherapy (atezolizumab or durvalumab) - You have not received any other cancer treatment between your first-line treatment and now (maintenance immunotherapy is OK) - Your general health allows you to be active and care for yourself (ECOG score 2 or less) - Brain metastases are allowed if they have been treated and are stable **You may NOT be eligible if...** - Your cancer progressed within 60 days of your first-line chemotherapy ending - You have received any additional cancer treatment (other than maintenance immunotherapy) since finishing first-line therapy - You are pregnant or breastfeeding - You have serious immune system disorders or conditions that would make immunotherapy unsafe Talk to your doctor to see if this trial is right for you.