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

This study aims to establish a safe and well tolerated dose of \[177Lu\]Lu-DOTA-TATE in combination with carboplatin, etoposide and atezolizumab in this setting and to assess preliminary efficacy of this combination treatment versus the combination of carboplatin, etoposide, and atezolizumab.The study will be essential to assess a new potential therapeutic option in participants with this aggressive cancer type.

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