Abstract
PURPOSE: To assess the technical and clinical feasibility of the phase I Hybrid trial (NCT01933568), combining SBRT of the primary tumor (PT) and fractionated radiotherapy (FRT) to the lymph nodes (LN). MATERIALS AND METHODS: Ten patients with stage III NSCLC with a peripheral PT<5cm were prospectively selected. The EQD2 corrected normal tissue dose parameters of the FRT plan of 24x2.75Gy to PT and 24x2.42Gy to LN (IMRT) was compared with 3x18Gy on the PT and 24x2.42Gy on the LN (VMAT) using a Wilcoxon signed-rank test. To anticipate differential motion between PT and LN, worst-case scenarios for OAR were calculated. Electronic portal imaging device (EPID) dosimetry analysis was performed to rule out dosimetric errors during delivery. RESULTS: The Hybrid plans revealed a significant decrease of esophagus EUD n=0.13, lung V5 and V20 and a significant increase in Dmax of the PRV of the mediastinal envelope. Plans were robust against differential motion of 5mm between PT and LN in 8 patients and failed in 2 patients due to spinal cord constraints. Average pass rates were >/=87% for EPID dosimetry. CONCLUSIONS: SBRT and FRT could be combined within the given OAR constraints. Safety will be assessed in the Hybrid trial.
