Inclusion Criteria:

- Pathologically (histologically or cytologically) proven diagnosis of Stage I NSCLC
(AJCC, 7th ed.), T1N0M0; note: T1N0 disease must be confirmed by FDG-PET/CT

The following primary cancer types are eligible: squamous cell carcinoma; adenocarcinoma;
large cell carcinoma/ large cell neuroendocrine carcinoma; non-small cell carcinoma not
otherwise specified.

- Patients with hilar or mediastinal lymph nodes ≤ 1 cm and no abnormal hilar or
mediastinal uptake on PET and CT will be considered N0. Mediastinal lymph node
biopsy is required for patients with visible nodes: patients with > 1 cm hilar or
mediastinal lymph nodes on CT or with nodes appearing as abnormal on PET (including
suspicious but nondiagnostic uptake). Such patients will not be eligible unless
directed biopsies of all abnormal lymph nodes are negative for cancer or these nodes
demonstrate a lack of change during the prior 6 months and thus are considered to be
non-malignant.

- The patient must be considered a reasonable candidate for surgical resection using a
lobectomy or pneumonectomy of the primary tumor within 6 weeks prior to registration,
according to the following criteria based on the American College of Chest Physicians
guidelines [165]:

- A qualified thoracic surgeon should make the determination that there would be a
high likelihood of negative surgical margins;

- Baseline FEV1 >60% predicted, postoperative predicted FEV1 >40% predicted;

- Diffusion capacity of the lung for carbon monoxide (DLCO) >60% predicted,
postoperative predicted DLCO > 40 % predicted;

- No baseline hypoxemia and/or hypercapnia;

- If the estimated postoperative FEV1 or DLCO <40% predicted indicates an
increased risk for perioperative complications, including death, from a standard
lung cancer resection (lobectomy or greater removal of lung tissue), then
cardiopulmonary exercise testing to measure maximal oxygen consumption (VO2max)
must be >60%;

- No severe pulmonary hypertension;

- No severe cerebral, acute or chronic cardiac, or peripheral vascular disease;

- Pleural effusion, if present, must be deemed too small to tap under CT guidance and
must not be evident on chest x-ray. Pleural effusion that appears on chest x-ray will
be permitted only if there is no evidence of malignancy after invasive cytologic
assessment.

- Appropriate stage for protocol entry, including no distant metastases, based upon the
following minimum diagnostic workup:

- History/physical examination, including documentation of weight within 6 weeks
prior to registration;;

- Evaluation by an experienced thoracic surgeon within 6 weeks prior to
registration;

- FDG-PET/CT scan for staging and RT plan within 4 weeks prior to registration;

- CT scan (preferably with intravenous contrast, unless medically contraindicated)
within 4 weeks prior to registration to include the entirety of both lungs, the
mediastinum, liver, and adrenal glands; primary tumor dimension will be measured
on CT scan.

- Zubrod Performance Status 0-1 within 6 weeks prior to registration;

- Age ≥ 18;

- For women of childbearing potential, a serum or urine pregnancy test must be negative
within 72 hours prior to registration;

- Women of childbearing potential and male participants who are sexually active must
practice adequate contraception during treatment if assigned to treatment with SBRT.

- Patients must provide study specific informed consent prior to study entry.

Exclusion Criteria:

- Direct evidence of regional or distant metastases after PET and surgical staging
studies, or synchronous primary malignancy or prior invasive malignancy in the past 3
years, with the following exceptions:

- carcinoma in situ;

- early stage skin cancer that has been definitively treated;

- when an invasive malignancy has been treated definitively and the patient has
remained disease free for ≥ 3 years;

- Primary tumors >3 cm;

- Prior systemic chemotherapy or thoracic surgery involving lobectomy or pneumonectomy;

- Prior radiotherapy to the region of the study cancer that would result in overlap of
radiation therapy fields;

- Pure bronchioloalveolar carcinoma subtype of non-small cell lung cancer;

- Active systemic, pulmonary, or pleural pericardial infection;

- Pregnancy or women of childbearing potential and men who are sexually active and not
willing/able to use medically acceptable forms of contraception; this exclusion is
necessary because the treatment involved in this study may be significantly
teratogenic.