Specialized Radiation Therapy and Chemotherapy in Treating Patients With Stage III Non-Small Cell Lung Cancer That Cannot Be Removed by Surgery

1. Histologically or cytologically documented non-small cell lung cancer 2. Stage IIIA or IIIB non-small cell lung cancer (NSCLC) per American Joint Committee on Cancer (AJCC) version 7; patients who present with N2 or N3 disease and an undetectable primary tumor are also eligible 3. Thoracic disease without supraclavicular or contralateral hilar involvement 4. When pleural fluid is visible on both computed tomography (CT) scan and on a chest x-ray, a pleuracentesis is required to confirm that the pleural fluid is cytologically negative; exudative pleural effusions are excluded regardless of cytology; patients with effusions that are minimal (i.e., not visible on chest x-ray) and too small to safely tap are eligible 5. No prior radiotherapy or chemotherapy for NSCLC 6. No prior mediastinal or thoracic radiotherapy 7. Patients with complete surgical resection of disease are not eligible, however; patients with surgical resection and measurable gross residual disease present on imaging are considered eligible 8. Patients must have measurable disease * Lesions that can be accurately measured in at least one dimension (longest diameter to be recorded) as \>= 2 cm with conventional techniques or as \>= 1 cm with spiral CT scan * Patients with non-measurable disease are not eligible; all other lesions, including small lesions (longest diameter \< 20 mm with conventional techniques or \< 10 mm with spiral CT scan) and truly nonmeasurable lesions; lesions that are considered non-measurable include the following: * Bone lesions * Leptomeningeal disease * Ascites * Pleural/pericardial effusion * Inflammatory breast disease * Lymphangitis cutis/pulmonis * Abdominal masses that are not confirmed and followed by imaging techniques * Cystic lesions 9. Eastern Cooperative Oncology Group (ECOG) performance status 0-1 10. No patients that are known to be pregnant or nursing 11. Granulocytes ≥ 1,500/μl Platelet count ≥ 100,000/μl Bilirubin ≤ 1.5 times upper limit of normal (ULN) Aspartate aminotransferase (AST) (serum glutamic oxalo-acetic transaminase \[SGOT\]) ≤ 2.0 times ULN Serum creatinine ≤ 1.5 times ULN OR calculated creatinine clearance \>= 70 mL/min FEV-1 ≥ 1.2 L/sec or 50% predicted