Inclusion Criteria:
* Histological confirmation of non-small cell cancer will not be required as primary goal of this phase II trial is to look at toxicity. However, all primary non-small cell lung cancers otherwise of following types are eligible: squamous cell carcinoma, adenocarcinoma, large cell carcinoma, bronchioalveolar cell carcinoma, or non-small cell carcinoma not otherwise specified.
* Eligible patients must have appropriate staging studies identifying them as specific subsets of AJCC stage I or II based on only one of the following combinations of TNM staging:
* T1, N0, M0
* T2 (≤ 5 cm), N0, M0
* Patients with hilar or mediastinal lymph nodes ≤ 1cm and no abnormal hilar or mediastinal uptake on PET will be considered N0. Patients with \> 1 cm hilar or mediastinal lymph nodes on CT or abnormal PET (including suspicious but non-diagnostic uptake) may still be eligible if directed tissue biopsy of all abnormally identified areas are negative for cancer. All patients with suspicious nodes will be evaluated for mediastinal and hilar staging with bronchoscopy and (if amenable) bronchoscopic biopsy (preferably navigational biopsy and/or endobronchial US guided biopsy).
* Zubrod performance status 0-2 within 4 weeks of study entry.
* Women of childbearing potential and male participants must use an effective contraceptive method.
* Evaluations required at time of study entry:
* History \& Physical by a radiation oncologist within 4 weeks of study entry;
* Vitals within 4 weeks of study entry;
* Evaluation by a thoracic surgeon (either via clinical examination and/or input at multidisciplinary tumor board) prior to study entry;
* PFTs: Routine spirometry, lung volumes, diffusion capacity, and arterial blood gases within 8 weeks prior to study entry;
* CT Chest within 6 weeks of study entry (preferably with intravenous contrast, unless medically contraindicated) - to include the entirety of both lungs, the mediastinum, liver, and adrenal glands; primary tumor dimension will be measured on this CT;
* Whole body positron emission tomography (PET) scan using FDG with adequate visualization of the primary tumor and draining lymph node basins in the hilar and mediastinal regions within 6 weeks prior to study entry.
* Informed consent signed by the subject and a member of the study team.
Exclusion Criteria:
* Patients with central tumors. Specifically; central location implies a tumor inside the zone of the proximal bronchial tree defined as a volume 2 cm in all directions around the proximal bronchial tree (carina, right and left main bronchi, right and left upper lobe bronchi, intermedius bronchus, right middle lobe bronchus, lingular bronchus, right and left lower lobe bronchi
* Evidence of regional or distant metastases after appropriate staging studies.
* Synchronous primary NSCLC.
* Those with prior malignancy in the past 2 years other than non-melanomatous skin cancer or in situ cancer or thyroid cancer.
* Previous lung or mediastinal radiotherapy.
* Plans for the patient to receive concomitant antineoplastic therapy (including standard fractionated radiotherapy, chemotherapy, biological therapy, vaccine therapy, and surgery) while on this protocol.
* Patients with active systemic, pulmonary or pericardial infection.
* Pregnant or lactating women, as treatment involves unforeseeable risks to the embryo or fetus.
