Stereotactic Body Radiotherapy (SBRT) Versus Stereotactic Body Proton Therapy (SBPT)

Inclusion Criteria: 1. Histological confirmation (by biopsy or cytology) or clinically diagnosed primary non-small cell lung cancer (NSCLC). The following primary cancer types are eligible: squamous cell carcinoma, adenocarcinoma, large cell carcinoma, bronchioloalveolar cell carcinoma, or non-small cell carcinoma not otherwise specified 2. Centrally located, defined as located within 2 cm of the central bronchial tree (carina, right and left main bronchi, right and left upper lobe bronchi, bronchus intermedius, right middle lobe bronchus, lingular bronchus, right and left lower lobe bronchi), major vessels (aorta, pulmonary artery trunk, left/right pulmonary artery/vein main branches, superior/inferior vena cava, brachiocephalic artery trunk or left/right brachiocephalic vein, left/right subclavian artery/vein), esophagus, heart, tracheal, pericardium, mediastinal pleural and brachial plexus, chest wall and vertebral body, but no direct invasion, Stage I (T1-T2a \<= 5 cm without main bronchus involvement), selective stage II ( selective T3 with involvement of mediastinal pleura, parietal pericardium,) based upon the following minimum diagnostic workup: 3. continued from criteria #2) History/physical examination including weight and assessment of Zubrod performance status within 2 months prior to registration; Evaluation by an experienced thoracic cancer clinician within 2 months prior to registration; computed tomography (CT) scan with intravenous contrast (unless medically contraindicated) of the entirety of both lungs and the mediastinum, most part of liver, and adrenal glands acquired within 2 months prior to registration must be available. The primary tumor dimension will be measured on the CT in lung window. If PET/CT is performed within 2 month prior to registration, CT of chest is recommended but nor required. Whole body fluorodeoxyglucose positron emission tomography (FDG-PET) within 3 months prior to registration with adequate visualization of the primary tumor and draining lymph node basins in the hilar and mediastinal regions and adrenal glands; Pulmonary function tests (PFTs): 4. continued from inclusion #3) Routine spirometry, lung volumes, diffusion capacity (within 3 months prior to registration). Patients with hilar or mediastinal lymph nodes \</= 1cm and no abnormal hilar or mediastinal uptake on PET will be considered N0. Patients with \> 1 cm hilar or mediastinal lymph nodes on CT or abnormal PET (including suspicious but non-diagnostic uptake) may still be eligible if directed tissue biopsy of all abnormally identified areas are negative for cancer. The primary tumor should be considered medically inoperable by an experienced thoracic cancer clinician for a standard lobectomy and mediastinal lymph node dissection/sampling procedure or patient refuses surgery. The patient may have underlying physiological medical problems that would prohibit a surgery due to a low probability of tolerating general anesthesia, the operation, the postoperative recovery period, or the removal of adjacent functioning lung. 5. continued from inclusion #4) These types of patients with severe underlying health problems are deemed "medically inoperable." Standard justification for deeming a patient medically inoperable based on pulmonary function for surgical resection of NSCLC may include any of the following: Baseline forced expiratory volume in 1 second (FEV1) \< 50% predicted, postoperative FEV1 \< 30% predicted, severely reduced diffusion capacity, baseline hypoxemia and/or hypercapnia, exercise oxygen consumption \< 50% predicted, severe pulmonary hypertension, diabetes mellitus with severe end organ damage, severe cerebral, cardiac, or peripheral vascular disease, or severe chronic heart disease. If the patient has medically resectable/operable disease but declines surgery after consulting with a thoracic surgeon, he/she will be considered eligible. 6. History of NSCLC treated with surgery and/or radiotherapy previously and disease has been cured or clinically no disease progression for more than 6 months, now isolated recurrent disease in lung parenchyma and without involvement of main bronchus, chest wall, hilar/mediastinal lymph nodes and critical mediastinal structures. Biopsy of recurrent disease is recommended. 7. Zubrod Performance Status 0-2; 8. Age \>/= 18 9. Women of childbearing potential and male participants must agree to use a medically effective means of birth control, such as condom/diaphragm and spermicidal foam, intrauterine device (IUD), or prescription birth control pills, throughout their participation in the treatment phase of the study. 10. The patient must provide study specific informed consent prior to study entry. Exclusion Criteria: 1. Direct evidence of hilar or mediastinal lymph nodes or distant metastases after appropriate staging studies. 2. Patients with active pulmonary or pericardial infection. 3. Pregnant or lactating women, as treatment involves unforeseeable risks to the embryo or fetus. 4. Patient pulmonary function showed that pre-bronchial dilator FEV1 \<25% or DLCO\<25%. 5. Patient currently requiring supplemental oxygen for his/her daily life. 6. Patient is pacemaker dependent. 7. Patients \</= 18 years of age.