Testing the Addition of the Drug Atezolizumab to the Usual Radiation Treatment for Patients With Early Non-small Cell Lung Cancer

Inclusion Criteria: * Patient must have histologically or cytologically proven stage I-IIA or limited T3N0M0 non-small cell lung cancer (NSCLC), without radiographic evidence of nodal or distant involvement (N0M0). Patient may have T3 disease with the exclusion of pericardial involvement. Patients with multifocal tumors with no more than two lesions confirmed or suspected to be synchronous early stage NSCLCs are eligible provided at least one lesion is histologically or cytologically proven to be NSCLC and meets one or more high-risk features * Disease must have one or more of the following high-risk features: * Tumor diameter \>= 2 cm (inclusive of any non-solid, ground glass component) as assessed by diagnostic CT * Tumor standard uptake value (SUV) max \>= 6.2 as assessed by FDG PET/CT * Moderately differentiated, poorly differentiated, or undifferentiated histology * Patient must have undergone diagnostic chest CT with or without contrast (IV contrast preferred) within 42 days prior to randomization. PET-CT may be used if the CT portion is of comparable diagnostic quality to a stand-alone CT. All disease must be assessed within 42 days prior to randomization * Patient must have undergone FDG PET/CT of chest within 90 days prior to randomization * Patient must not have evidence of hilar or mediastinal nodal involvement. Any patient with radiographically suspicious hilar or mediastinal nodes (including features such as non-calcified nodes with a short axis diameter …