A phase I dose escalation trial has been completed at Indiana University for treatment of medically inoperable patients with stage I NSCLC.26, 27 SBRT was administered with large doses per fraction in an extracranial stereotactic body frame, which includes a system for decreasing breathing motion. The starting dose was 8 Gy times 3 (24 Gy total), and fraction dose was escalated by 2 Gy per fraction for each cohort. The target lesion was outlined by a physician and designated as the gross tumor volume (GTV). An additional 0.5 cm in the axial plane and 1.0 cm in the longitudinal plane was added to the GTV to constitute the PTV based on validation measurements for this commercially available system.23, 28, 29 Typically, 7 to 10 non-coplanar beams were used to encompass the PTV. Dose was prescribed to the 80% isodose line. However, higher isodoses occurred within the center of the target mimicking the heterogeneous dose profile common to intracranial stereotactic radiosurgery. The treatment isocenter was identified with 3-D coordinates defined stereotactically and localized on verniers attached to the frame. No skin or bony landmarks were used to set the treatment isocenter; however, orthogonal port films were used on a daily basis for isocenter verification.30 Separate dose escalations were carried out independently for patients with T1 versus T2 small (≤ 5 cm) versus T2 large (5-7 cm) tumors at diagnosis.