Inclusion Criteria:

          -  Age > 18 years.

          -  ECOG performance status (PS) 0, 1, or 2.

          -  Radiographic findings consistent with non-small cell lung cancer, including lesions
             with ground glass opacities with a solid component of 50% or greater. Those with
             ground glass opacities and <50% solid component will be excluded.

          -  The primary tumor in the lung must be biopsy confirmed non-small cell lung cancer
             within 180 days prior to randomization.

          -  Tumor ≤ 4 cm maximum diameter, including clinical stage IA and selected IB by PET/CT
             scan of the chest and upper abdomen performed within 180 days prior to randomization.
             Repeat imaging within 90 days prior to randomization is recommended for re-staging but
             is not required based on institutional norms.

          -  All clinically suspicious mediastinal N1, N2, or N3 lymph nodes (> 1 cm short-axis
             dimension on CT scan and/or positive on PET scan) confirmed negative for involvement
             with NSCLC by one of the following methods: mediastinoscopy, anterior mediastinotomy,
             EUS/EBUS guided needle aspiration, CT-guided, video-assisted thoracoscopic or open
             lymph node biopsy within 180 days of randomization.

          -  Tumor verified by a thoracic surgeon to be in a location that will permit sublobar
             resection.

          -  Tumor located peripherally within the lung. NOTE: Peripheral is defined as not
             touching any surface within 2 cm of the proximal bronchial tree in all directions. See
             below. Patients with non-peripheral (central) tumors are NOT eligible.

          -  No evidence of distant metastases.

          -  Availability of pulmonary function tests (PFTs - spirometry, DLCO, +/- arterial blood
             gases) within 180 days prior to registration. Patients with tracheotomy, etc, who are
             physically unable to perform PFTs (and therefore cannot be tested for the Major
             criteria in 3.1.11 below) are potentially still eligible if a study credentialed
             thoracic surgeon documents that the patient's health characteristics would otherwise
             have been acceptable for eligibility as a high risk but nonetheless operable patient
             (in particular be eligible for sublobar resection).

          -  Patient at high-risk for surgery by meeting a minimum of one major criteria or two
             minor criteria

          -  Major Criteria

               -  FEV1 ≤ 50% predicted (pre-bronchodilator value)

               -  DLCO ≤ 50% predicted (pre-bronchodilator value)

          -  Minor Criteria

               -  Age ≥75

               -  FEV1 51-60% predicted (pre-bronchodilator value)

               -  DLCO 51-60% predicted (pre-bronchodilator value)

               -  Pulmonary hypertension (defined as a pulmonary artery systolic pressure greater
                  than 40mm Hg) as estimated by echocardiography or right heart catheterization

               -  Study credentialed thoracic surgeon believes the patient is potentially operable
                  but that a lobectomy or pneumonectomy would be poorly tolerated by the patient
                  for tangible or intangible reasons. The belief must be declared and documented in
                  the medical record prior to randomization.

               -  Poor left ventricular function (defined as an ejection fraction of 40% or less)

               -  Resting or Exercise Arterial pO2 ≤ 55 mm Hg or SpO2 ≤ 88%

               -  pCO2 > 45 mm Hg

               -  Modified Medical Research Council (MMRC) Dyspnea Scale ≥ 3.

          -  No prior intra-thoracic radiation therapy for previously identified intra-thoracic
             primary tumor (e.g. previous lung cancer) on the ipsilateral side. NOTE: Previous
             radiotherapy as part of treatment for head and neck, breast, or other non-thoracic
             cancer is permitted so long as possible radiation fields would not overlap. Previous
             chemotherapy or surgical resection specifically for the lung cancer being treated on
             this protocol is NOT permitted.

          -  No prior lung resection on the ipsilateral side.

          -  Non-pregnant and non-lactating. Women of child-bearing potential must have a negative
             urine or serum pregnancy test prior to registration. Peri-menopausal women must be
             amenorrheic > 12 months prior to registration to be considered not of childbearing
             potential.

          -  No prior invasive malignancy, unless disease-free for ≥ 3 years prior to registration
             (exceptions: non-melanoma skin cancer, in-situ cancers).

          -  Ability to understand and the willingness to sign a written informed consent.

        Exclusion Criteria:

          -  evidence of distant metastases

          -  prior intra-thoracic radiation therapy. NOTE: Previous radiotherapy as part of
             treatment for head and neck, breast, or other non-thoracic cancer is permitted so long
             as possible radiation fields would not overlap. Previous chemotherapy or surgical
             resection specifically for the lung cancer being treated on this protocol is NOT
             permitted. No prior lung resection on the ipsilateral side.

          -  pregnant and lactating women

          -  prior invasive malignancy, unless disease-free for ≥ 3 years prior to registration
             (exceptions: non-melanoma skin cancer, in-situ cancers).