Pemetrexed Disodium, Carboplatin, and Radiation Therapy With or Without Cetuximab in Treating Patients With Stage III Non-Small Cell Lung Cancer

1. Histologically or cytologically documented NSCLC, including squamous cell carcinoma, adenocarcinoma including bronchoalveolar cell, and large cell anaplastic carcinoma (including giant and clear cell carcinomas) 2. Eligible Disease Stages: Inoperable IIIA and Selected IIIB - Patients entered must be considered unresectable or inoperable. Patients do not need to have a mediastinoscopy. A size of 2 cm or greater by CT is a sufficient criterion for the diagnosis of mediastinal lymph node (N2 or N3) involvement by malignancy. If the largest mediastinal lymph node is less than 2 cm in diameter, a biopsy confirmation of mediastinal nodal involvement is required. 1. The following patients are eligible: * Patients must be M0 * Patients with any T with N2 or N3 are eligible * Patients with T3, N1-N3 disease are eligible if deemed unresectable * Patients with T4, any N are eligible provided the T4 status is not determined because of malignant effusion * Patients with contralateral mediastinal disease (N3) are eligible if all gross disease can be encompassed in the radiation field in accordance with the homogeneity criteria * Patients with a pleural effusion, which is a transudate, cytologically negative and non-bloody, are eligible if the radiation oncologist feels the tumor can be encompassed within a reasonable field of radiotherapy * If a pleural effusion can be seen on the chest CT but not on CXR and is too small to tap, the patient will be eligible. Patients who develop a new pleural effusion after thoracotomy or other invasive thoracic procedure will be eligible. 2. The following patients are NOT eligible: * Patients with T3, N0 disease * Patients with M1 disease * Patients with atelectasis of the entire lung * Patients with direct invasion of vertebral body * Patients with scalene, supraclavicular, or contralateral hilar node involvement * Patients with exudative, bloody, or cytologically malignant effusions 3. Patients must have Measurable Disease: Lesions that can be accurately measured in at least one dimension (longest diameter to be recorded) as ≥ 20 mm with conventional techniques or as ≥10 mm with spiral CT scan. Lesions that are not considered measurable include bone lesions, leptomeningeal disease, ascites, pleural/pericardial effusion, abdominal masses that are not confirmed and followed by imaging techniques, cystic lesions and tumor lesions situated in a previously irradiated area. 4. Prior Therapy: ≥ 2 weeks since formal exploratory thoracotomy. No prior chemotherapy for NSCLC, chest radiation therapy or therapy that specifically and directly targets the EGFR pathway 5. ECOG performance status 0-1 6. Positron Emission Tomography (PET) using 18 fluorodeoxyglucose (FDG) must be negative for distant metastasis. PET imaging is mandatory. 7. Weight loss of ≤ 10% in the past 3 months 8. No "currently active" second malignancy other than non-melanoma skin cancers. Patients are not considered to have a "currently active" malignancy if they have completed therapy and are considered by their physician to be at less than 30% risk of relapse. 9. Non-pregnant and non-nursing because of significant risk to the fetus/infant 10. Age ≥ 18 years 11. No patients with uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness. 12. No HIV-positive patients receiving combination anti-retroviral therapy because patients with immune deficiency are at increased risk of lethal infections when treated with marrow-suppressive therapy 13. No known history of hypersensitivity to carboplatin, pemetrexed or a monoclonal antibody 14. Required Initial Laboratory Values: 1. Granulocytes ≥ 1,500/mcl 2. Platelets ≥ 100,000/mcl 3. Calculated Creatinine Clearance ≥ 45 ml/min 4. Bilirubin \< 1.5 x ULN 5. AST/ALT \< 3 x ULN 6. Alkaline Phosphatase \< 3 x ULN