SBRT combined with concurrent chemoradiation in stage III NSCLC: Feasibility study of the phase I Hybrid trial.

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).

CONCLUSIONS

SBRT and FRT could be combined within the given OAR constraints. Safety will be assessed in the Hybrid trial.

RESULTS

The Hybrid plans revealed a significant decrease of esophagus EUD n = 0.13, lung V5 and V20 and a significant increase in D_max of the PRV of the mediastinal envelope. Plans were robust against differential motion of 5 mm 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.

MATERIALS AND METHODS

Ten patients with stage III NSCLC with a peripheral PT < 5 cm were prospectively selected. The EQD₂ corrected normal tissue dose parameters of the FRT plan of 24×2.75 Gy to PT and 24×2.42 Gy to LN (IMRT) was compared with 3×18 Gy on the PT and 24×2.42 Gy 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.