 Phase II of this trial will consist of 26 patients who will undergo a specialized form of SABR radiotherapy specifically designed to take full advantage of the real-time tumor tracking ability of the transponder beacons. Specifically, SABR in phase II will consist of smaller radiotherapy treatment volumes employing respiratory gating and smaller planning target volume expansion margins given the superior tumor location telemetry afforded by the beacons. Comparative dosimetric analyses contrasting the traditional ITVPTV style treatments to those with reduced ITVPTV margins achieved via Calypso guided SABR will be performed. Patient self-reported quality of life and toxicity assessments will be collected with the goal of facilitating power and sample size calculations for the design of a larger phase III randomized controlled trial of Calypso guided SABR treatment in the future 