FLARE RT for Patients With Stage IIB-IIIB Non-small Cell Lung Cancer: Personalizing Radiation Therapy Using PET/CT and SPECT/CT Imaging

Inclusion Criteria: * Pathologically proven (either histologic or cytologic) diagnosis of stage IIB-IIIB non-small cell lung cancer (NSCLC); according to American Joint Committee on Cancer (AJCC) staging, 7th edition * Staging workup must include: brain imaging (CT head or magnetic resonance imaging \[MRI\] brain) and PET/CT * Pleural effusions must have cytology to rule out malignant involvement unless too small to undergo thoracentesis per radiology * Patients must be considered unresectable or inoperable * Patient must not have received prior radiation for this lung cancer * Patients must be having concurrent chemotherapy * Nodal recurrences can be treated on this protocol but prior curative surgery for lung cancer must have been at least 6 months prior to the nodal recurrence * Patients must have measurable or evaluable disease that is FDG avid with standardized uptake value (SUV) \> 3 on PET/CT * Zubrod performance status 0-1 * PFTs including forced expiratory volume in 1 second (FEV1) within 26 weeks prior to registration; for FEV1, the best value obtained pre- or post-bronchodilator must be \>= 0.8 liters/second or \>= 50% predicted * Blood cell count (CBC)/differential obtained within 8 weeks prior to registration on study * Absolute neutrophil count (ANC) \>= 1,800 cells/mm\^3 * Platelets \>= 100,000 cells/mm\^3 * Hemoglobin \>= 10.0 g/dl (Note: The use of transfusion or other intervention to achieve hemoglobin (Hgb) \>= 10.0 g/dl is acceptable) * Serum creatinine within normal institutional limits or creatinine clearance \>= 40 ml/min * Bilirubin must be within or below normal institutional limits * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 2.5 x the institutional upper limit of normal (IULN) * Patient must sign study specific informed consent prior to study entry Exclusion Criteria: * \> 10% unintentional weight loss within the past month * Prior invasive malignancy (except non-melanomatous skin cancer) unless disease free for a minimum of 3 years; non-invasive conditions such as carcinoma in situ of the breast, oral cavity, or cervix are all permissible * Prior radiotherapy to the region of the study cancer that would result in overlap of radiation therapy fields * Pregnancy or women of childbearing potential and men who are sexually active and not willing/able to use medically acceptable forms of contraception