Computed Tomography-Guided Stereotactic Adaptive Radiotherapy (CT-STAR) for the Treatment of Central and Ultra-Central Early-Stage Non-Small Cell Lung Cancer

Inclusion Criteria: * Histologically or radiographically diagnosed stage I-IIA (AJCC, 8th ed.) non-small cell lung cancer or mediastinal recurrent non-small cell lung cancer with plans to be treated with definitive intent SBRT alone. * Clinical AJCC stage I defined as stage 1A1 (T1a1N0M0, T1a tumor less than or equal to 1 cm), stage 1A2 (T1bN0M0, T1b tumor between 1 and 2 cm), and stage 1A3 (T1cN0M0, T1c tumor between 2 and 3 cm). * Clinical AJCC stage IB defined as T2aN0M0, T2a tumor between 3 and 4 cm. * Clinical AJCC stage IIA defined as T2bN0M0, T2b tumor between 4 and 5 cm. * Lesions must be defined as central or ultra-central according to the Hilus-trial13 criteria: * Central lesions are defined as lesions 1 cm or less from the trachea, carina, main bronchi, bronchus intermedius, or lobar bronchi. * Ultra-central lesions are defined as lesions touching the trachea, carina, main bronchi, bronchus intermedius, or lobar bronchi. Lesions that touch the esophagus, great vessels, or heart may also be included as ultra-central. * Tumor coverage is deemed adequate in simulation treatment planning as determined by the treating and study physicians. Specifically, the dose to 98% of the GTV must be greater than 45 Gy. * Note: patients with inadequate tumor coverage at simulation will be considered screen-failures and treated off-protocol as per institutional standard-of-care. \*In a in silico analysis of these patients, only 1/6 patients screen-failed based on this inclusion criteria. * Patients should be able to hold their breath for 10 seconds. * Inoperable disease or patient has refused/declined surgery. * Deemed medically fit for SBRT by the treating physician. * At least 18 years of age. * Zubrod Performance Status 0-2 within 30 days prior to registration. * Appropriate stage for protocol entry based upon the following minimum diagnostic workup. * History/physical examination within 30 days prior to registration. * FDG-PET/CT scan and/or CT chest (with or without contrast) for staging within 60 days prior to registration. * Adequate bone marrow and hemostasis function determined no more than 30 days prior to registration, defined as follows: * Platelets ≥ 150,000 cells/mm3 * Hemoglobin ≥ 8 g/dl * Able to understand and willing to sign an IRB approved written informed consent. Exclusion Criteria: * Lesions appearing to extend through the bronchial or great vessel walls on CT imaging. * Prior or concurrent malignancies, unless the natural history of the prior or concurrent malignancy does not have the potential to interfere with the interpretation of the results of the study. * Patients with a pre-existing, active diagnosis of metastatic cancer. * Severe, active comorbidity, defined as follows: * Unstable angina, history of myocardial infarction and/or congestive heart failure requiring hospitalization within the last 6 months; * Acute bacterial or fungal infection requiring intravenous antibiotics at the time of registration; * Chronic Obstructive Pulmonary Disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of registration; * Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects; note, however, that laboratory tests for liver function and coagulation parameters are not required for entry into this protocol. * Past history of radiotherapy within the projected treatment field of any of the disease sites to be treated by CT-guided SBRT. * Pregnant and/or breastfeeding. Patient must have a negative pregnancy test within 14 days of the start of SBRT.