Stereotactic Body Radiotherapy (SBRT) Versus Sublobar Resection for High-Risk Patients Non-Small Lung Cancer

Inclusion Criteria * Patients must have a suspicious lung nodule for clinical stage I NSCLC. * Pathologic confirmation at the time of surgery is acceptable. Patients randomized to SBRT require core biopsy for diagnosis prior to treatment. * Patient must have a mass ≤ 5 cm maximum diameter by CT size estimate that is clinical stage I (T1N0, T2N0) * Patient must have a CT scan of the chest and upper abdomen and PET-scan within 60 days prior to date of registration. * Patient must have an Eastern Cooperative Oncology Group (ECOG) or Zubrod performance status 0, 1, or 2. * Patient must meet at least one major criteria or meet a minimum of two minor criteria as described below: Major Criteria: * Forced expiratory volume in one second (FEV1) ≤ 50% predicted * Carbon monoxide diffusing capacity (DLCO) ≤ 50% predicted Minor Criteria: * Age ≥75 * FEV1 51-60% predicted * DLCO 51-60% predicted * Pulmonary hypertension (defined as a pulmonary artery systolic pressure greater than 40 mmHg) as estimated by echocardiography or right heart catheterization * Poor left ventricular function (defined as an ejection fraction of 40% or less) * Resting or Exercise Arterial oxygen partial pressure (pO2) ≤ 55 mm Hg or blood oxygen saturation (SpO2) ≤ 88% * pCO2 \> 45 mm Hg * Modified Medical Research Council (MMRC) Dyspnea Scale ≥ 3. Exclusion Criteria * Patient must not have had previous intra-thoracic radiation therapy. * No prior malignancy except adequately treated non-melanoma skin cancer, in situ cervical cancer, localized prostate cancer, stage 0 Chronic lymphocytic leukemia (CLL), or other cancer disease-free \> 3 yrs.