The goal of this clinical research study is to evaluate the outcome of a standard radiation treatment called stereotactic radiotherapy (SRT) for NSCLC.

Specifically, researchers want to learn if standard SRT has as good of an outcome at 3 years after the procedure. The safety of the study treatment will also be analyzed.

The Study Treatment:

The treatment being used in this study is considered standard, but researchers want to see its outcome in early-stage NSCLC.

The radiation (SRT) in this study is designed to kill tumor cells by using beams of radiation aimed directly at the tumor from different angles. The doctor uses computed tomography (CT) scans to plan exactly where to direct the beams to go. A computer is used to show the location, size, and shape of the tumor. SRT is designed to cause less damage to normal tissue than surgery, and it also may allow a higher dose of radiation to be given to the tumor than if other forms of radiation therapy were used.

The SRT in this study will be performed using a radiation machine called Linear Accelerator (Linac).

Study Group:

If you are found to be eligible to take part in this study, you will receive SRT (as an out-patient) once a day for 3-4 days in a row. You will be asked to hold still during the entire treatment (for about 1 to 1 1/2 hours each time). The machine will move around you, but you will not see or feel anything (similar to getting an x-ray).

Follow-Up Visits:

During the treatment period, you will be seen by a doctor and/or research nurse in order to check for any side effects. A physical exam will be performed, and your medical history will be recorded. These follow-up procedures will be done once on any day of your SRT.

A physical exam will be performed and your medical history will be recorded at 6 and 12 months, then at 1 1/2, 2, 3, 4, and 5 years after your SRT. If the doctor decides it is necessary, you will have a chest x-ray to check the status of the disease.

At 6 to 12 months after SRT, you will have either a PET-CT scan or CT scan to check the status of the disease.

At 1 year after SRT, you will have breathing tests to check your lung function. You will also have a CT scan to check the status of your disease.

At 1 1/2 year and then at 2, 3, 4, and 5 years after SRT, you will have a CT scan to check the status of your disease.

Possible Re-Treatment On Study:

If one of your follow-up CT scans shows that the tumor has come back in the same location or very close, you will have a PET scan and a tumor biopsy. The purpose is to confirm the status of the disease. To collect a tumor biopsy, the affected area is numbed with anesthetic, and a small amount of tissue is withdrawn through a large needle.

As soon as the results of the scan and biopsy come back, the study doctor will discuss with you the different treatment options. You may receive surgery, radiation therapy, or chemotherapy, depending on the status of the disease. You will receive a separate consent form that describes the treatment in more detail, as well as the risks.

After this "re-treatment", you will stay on the same schedule for study follow-up visits as you were following before.

Length of Study Participation:

Your participation in this study will be over after the 5-year follow-up visit.

This is an investigational study. The treatment is commercially available and considered standard for early-stage NSCLC. This includes the use of the Linac radiation machine, which is FDA approved and commercially available.

Up to 80 treated patients will take part in this study. All will be enrolled at MD Anderson.

Inclusion Criteria:

1. Histological confirmation of non-small cell cancer will be required by either biopsy or cytology. The following primary cancer types are eligible: squamous cell carcinoma, adenocarcinoma with or without BAC features, large cell carcinoma with or without neuroendocrine features, neuroendocrine carcinoma, bronchioloalveolar cell carcinoma, or non-small cell carcinoma not otherwise specified.
2. Eligible patients must have appropriate staging studies identifying them as specific subsets of the revised IASLC stage IA based on the following combination of TNM staging: T1a,N0,M0 or T1b,N0,M0
3. A PET/CT scan is required. Patients with hilar or mediastinal lymph nodes with short axis diameter </= 1cm and no abnormal hilar or mediastinal uptake on PET will be considered N0. Patients with > 1 cm short axis diameter of 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. Solitary pulmonary lesions </= 6mm will not be considered significant.
4. Patients must be considered a candidate for surgical resection of the primary tumor. Standard justification for deeming a patient medically operable based on pulmonary function for surgical resection of NSCLC may include any of the following: Baseline FEV1 > 40% predicted, post-operative predicted FEV1 > 30% predicted, diffusion capacity > 40% predicted, absent baseline hypoxemia and/or hypercapnia, exercise oxygen consumption > 50% predicted, absent severe pulmonary hypertension, absent severe cerebral, cardiac, or peripheral vascular disease, and absent severe chronic heart disease.
5. Patients must be >/= 18 years of age.
6. The patient's Zubrod performance status must be Zubrod 0-2.
7. PET/CT scan to include both lungs, the mediastinum, and adrenal glands; Primary tumor dimension will be measured on diagnostic CT and again on simulation CT. Must be done within 10 weeks prior to study entry.
8. Mediastinoscopy or endobronchial ultrasound (EBUS) guided biopsy of mediastinal lymph nodes is required for all patients. Must be done within 10 weeks of study entry.
9. MRI or CT scans of Brain if there are symptoms or signs suggesting brain metastases, must be done within 10 weeks prior to study entry.
10. Invasive Mediastinal Staging - All patients with CT and/or PET evidence of hilar (level 10) or mediastinal lymph nodes > 1.0 cm in the shortest diameter must be staged by either cervical mediastinoscopy, esophageal endoscopic ultrasound guided biopsy, or endobronchial ultrasound guided biopsy.
11. Patients must sign a study-specific consent form.
12. Patients (men and women) of child bearing potential should use an effective (for them) method of birth control throughout their participation in this study.

Exclusion Criteria:

1. Patients with primary tumors > 3 cm.
2. Patients with well-differentiated neuroendocrine carcinoma (carcinoid tumor).
3. Direct evidence of regional or distant metastases after appropriate staging studies, or synchronous primary or prior malignancy in the past 3 years other than nonmelanomatous skin cancer or in situ cancer.
4. Previous lung or mediastinal radiotherapy.
5. Plans for the patient to receive other concomitant local therapy (including standard fractionated radiotherapy and surgery) while on this protocol except at disease progression.
6. Pregnant or lactating women, as treatment involves unforeseeable risks to the embryo or fetus.
7. Cannot achieve acceptable SABR planning to meet minimal requirement of target coverage and dose-volume constraints of critical structures (see RT techniques).