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.