Comparing Photon Therapy To Proton Therapy To Treat Patients With Lung Cancer

Inclusion Criteria: * Histologically or cytologically proven diagnosis of non-small cell lung cancer * Clinical American Joint Committee on Cancer (AJCC) (AJCC, 7th ed.) II, IIIA or IIIB (with non-operable disease; non-operable disease will be determined by a multi-disciplinary treatment team within 60 days prior to registration; note: for patients who are clearly nonresectable, the case can be determined by the treating radiation oncologist and/or a medical oncologist or pulmonologist * Patients who present with N2 or N3 disease and an undetectable NSCLC primary tumor are eligible * Patients who refuse surgery are eligible * Patients who develop local recurrence after surgery and rendered candidate for definitive concurrent chemoradiation are also eligible * Patients who have received systemic treatment (up to 4 cycles of induction chemotherapy, or up to 6 months of targeted therapy) are eligible * Appropriate stage for protocol entry, including no distant metastases, based upon the following minimum diagnostic workup: * History/physical examination within 30 days prior to registration including resting heart rate; * Fludeoxyglucose F 18 (FDG)-positron emission tomography (PET)/computed tomography (CT) scan for staging within 60 days prior to registration * Magnetic resonance imaging (MRI) scan with contrast of the brain (preferred) or CT scan of the brain with contrast within 60 days prior to registration; * Forced expiratory volume in one second (FEV1) \…