This clinical trial is focused on studying treatments for patients with early-stage non-small cell lung cancer (NSCLC), a type of lung cancer that is not small cell in nature. The study involves two main treatments. The first treatment is with a medication called durvalumab, also known by its code name MEDI4736, which is given alongside a type of radiation therapy called stereotactic body radiation therapy (SBRT). The second treatment involves a medication called osimertinib, also known as AZD9291, which is given after radiation therapy to patients whose cancer has a specific change in the EGFR gene, making it more sensitive to this treatment.

The purpose of the study is to evaluate how effective these treatments are in managing early-stage NSCLC. For the durvalumab group, the study will compare the effects of durvalumab combined with SBRT to a placebo combined with SBRT. For the osimertinib group, the study will assess the effects of osimertinib following SBRT in patients with an EGFR mutation. The study will follow participants over a period to observe the progression of the disease and overall survival rates.

Participants in the study will receive either the active treatment or a placebo, depending on the group they are in. The study will involve regular monitoring and assessments to track the progress of the disease and any side effects from the treatments. The study aims to provide valuable information on the effectiveness of these treatments in improving outcomes for patients with early-stage NSCLC.