This clinical trial is focused on studying treatments for Limited Stage Small-Cell Lung Cancer (LS-SCLC). The study will explore the effectiveness of two medications, Durvalumab and Tremelimumab, either used together or with a placebo. Durvalumab is also known by its code name MEDI4736. The purpose of the study is to evaluate how well these treatments work in patients who have not experienced disease progression after receiving a combination of chemotherapy and radiation therapy.

Participants in the study will receive one of the following treatments: Durvalumab alone, a combination of Durvalumab and Tremelimumab, or a placebo. The medications are administered as a solution for infusion, which means they are given directly into the bloodstream through a vein. The study will last for a period of up to 24 months, during which the effects of the treatments will be monitored and compared.

The trial aims to provide valuable information on the potential benefits of these treatments for patients with Limited Stage Small-Cell Lung Cancer. By participating in this study, researchers hope to determine if these medications can help improve the outcomes for patients who have already undergone initial treatment with chemotherapy and radiation. The study is conducted in a double-blind manner, meaning neither the participants nor the researchers know who is receiving which treatment, to ensure unbiased results.