A Study of [177Lu]Lu-DOTA-TATE in Newly Diagnosed ES-SCLC Patients in Combination With Carboplatin, Etoposide and Atezolizumab

Key Inclusion Criteria: * Participant is \>= 18 years on the day of signing informed consent form * Histologically or cytologically confirmed ES-SCLC * Presence of measurable disease * No prior systemic treatment for ES-SCLC (except the first cycle of chemotherapy with or without atezolizumab of the induction period * ECOG status =\< 1 * Provision of tumor tissue to support exploratory biomarker analysis * Life expectancy of \>= 6 months Key Exclusion Criteria: * Participant has received prior therapy with an antibody or drug against immune checkpoint pathways * Active autoimmune diseases or history of autoimmune diseases that may relapse * Severe chronic or active infections (including active tuberculosis, HBV, or HCV infection) requiring systemic antibacterial, antifungal or antiviral therapy within 2 weeks before Cycle 1 Day 1 * Any major surgical procedure requiring general anesthesia =\< 28 days before Cycle 1 Day 1 * History or current diagnosis of electrocardiogram (ECG) abnormalities indicating significant risk of safety for participants participating in the study * Known hypersensitivity to the active substances or any of the excipients of the study drugs * Concurrent participation in another therapeutic clinical study