• Age 18 or older

• Any patient with a preliminary diagnosis of stage I Non-Small Cell Lung Cancer (NSCLC), whether pathologically proven by biopsy, or highly suspicious by radiographic imaging. \[Participants will ultimately need biopsy confirmation before enrolling\]

• Primary tumor size less than or equal to 5 cm by CT (may include CT images from PET/CT)

• Karnofsky performance status greater than or equal to 70

• Participant has willingness and ability to provided informed consent for participation

• Biopsy proven non-small cell lung cancer

• Participant's case reviewed at multidisciplinary conference

• Tumor size less than or equal to 5cm (measured on the most recent CT images available, and may include PET/CT images)

• Tumor is equal to or greater than 1.0cm from the trachea, esophagus, brachial plexus, 1st bifurcation of the proximal bronchial tree, or spinal cord (measured on the most recent CT images available, and may include PET/CT images).

• Mandatory FDG-PET/CT within 60 days of the randomization date (note: FDG-PET/CT may need to be repeated prior to treatment if outside of this requirement)

• Mandatory pathological assessment of any lymph nodes \>10mm with a SUV \>2.5 seen on FDG- PET/CT

• Mandatory biopsy of any additional concerning lesions seen on FDG-PET/CT, to make better determination that the patient is not harboring metastatic disease or a secondary primary malignancy.

• Pre-operative FEV1 greater than or equal to 40% of predicted value and pre-operative DLCO greater than or equal to 40% of predicted value.

• Formally evaluated and documented by a local thoracic surgeon to be medically fit to undergo a complete anatomic pulmonary resection (wedge resection not allowed)

• Formally evaluated and documented by a local radiation oncologist to be eligible to receive protocol-defined stereotactic radiotherapy

• Participant willingness to be randomized