This study checks if combining radiation therapy and atezolizumab helps people with stage II or III non-small cell lung cancer (NSCLC). Radiation therapy uses strong rays to kill cancer cells. Atezolizumab is a monoclonal antibody, a type of treatment that helps the immune system fight cancer. This study wants to see how safe these treatments are together and if they help patients.

• The study lasts up to 12 months, with treatment cycles every 21 days.
• Participants will undergo CT or MRI scans and give blood samples during the study.
• Follow-up visits occur at 6 weeks, then every 12 months for 1 year, and every 6 months up to 3 years.

Participants must have NSCLC and meet specific health criteria. They should not be able to have surgery or chemoradiation. They must have measurable disease through CT or MRI scans and fit certain health standards, like having good blood counts and organ function. People with certain health conditions or who are pregnant cannot join. Participants must use effective contraception during and after the study. The study also checks for infections like hepatitis or HIV before joining.