Phase IB/II Trial Of Dose-Deescalated 3-Fraction Stereotactic Body Radiotherapy For Centrally Located Lung Cancer

Inclusion Criteria: 1. Lung tumors will be ≤ 5 cm and centrally located, meaning any portion of gross tumor volume located within 2 cm of (but not abutting) the proximal bronchial tree (trachea, carina, right and left main bronchi, right and left upper lobe bronchi, bronchus intermedius, right middle lobe bronchus, lingular bronchus, right and left lower lobe bronchi), or within 2 cm of (whether abutting or not) major vessels, esophagus, or heart (based on RTOG and MD Anderson Cancer Center definitions 33,34). Multiple concurrent isocenters are allowed if at least one tumor meets the above criteria, and if all dose constraints for the plan summation can be met. These concurrent tumors other than study target lesion can be treated as per SOC and does not necessarily have to meet the above size limit. The PI will review and prospectively approve any lesions abutting these organs. 2. ECOG Performance Status of 0-2 3. Age \> 18 4. Patients must sign a study-specific consent form. Exclusion Criteria: 1. Prior history of radiotherapy near target lesion resulting in overlapping treatment fields. Previously irradiated will be defined as OAR structures receiving the following doses (in \<3Gy per fraction): * Spinal cord previously irradiated to \> 40 Gy * Brachial plexus previously irradiated to \> 50 Gy * Small intestine, large intestine, or stomach previously irradiated to \> 45Gy * Brainstem previously irradiated to \> 50 Gy * Lung previously irradiated with prior V20Gy \> 35% 2. Active systemic, pulmonary, or pericardial infection 3. Interstitial pneumonia or extensive and symptomatic interstitial fibrosis of the lung 4. Pregnant or lactating 5. Any other medical condition or reason that, in the opinion of the investigator, would preclude study participation