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
• Biopsy confirmed non-small cell lung cancer
• Tumor ≤ 4 cm maximum diameter, including clinical stage IA and selected IB by PET/CT scan of the chest and upper abdomen performed within 60 days prior to registration
• 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
• Tumor verified by a thoracic surgeon to be in a location that will permit sublobar resection
• Tumor located peripherally within the lung
  • Peripheral is defined as not touching any surface within 2 cm of the proximal bronchial tree in all directions
• No evidence of distant metastases
• Availability of pulmonary function tests (PFTs - spirometry, DLCO, +/- arterial blood gases) within 90 days prior to registration
• Patients with tracheotomy, etc, who are physically unable to perform PFTs (and therefore cannot be tested for the Major criteria ) 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)
• At high-risk for surgery by meeting a minimum of one major criteria or two minor criteria
• No prior intra-thoracic radiation therapy
• 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 within 60 days 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
  • 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 
• 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)