18F-FDG PET/CT-Guided Dose Escalation In Small Cell Lung Cancer Using a Novel Combined X-Ray and γ-Ray Radiotherapy Technique
Abstract
Purpose
This study evaluates the dosimetric advantages of TaiChi, a novel radiotherapy platform that integrates 6 MV linacbased volumetric modulated arc therapy (VMAT) with γray stereotactic radiotherapy, for the treatment of small cell lung cancer (SCLC).
Methods
Twelve SCLC cases were retrospectively analyzed. TaiChi plans were compared with conventional VMAT plans. Prescription doses were standardized at 60 Gy to the planning target volume (PTV) and 6 Gy to the boost volumes (PGTV and PGTVLn), which were delineated using 18F-FDG PET/CT imaging. Conventional plans were generated using the Varian Eclipse 13.5 treatment planning system (TPS) with VMAT. TaiChi plans were created using the RTPRO TPS (OUR United Corp., China), leveraging its dualmodality capability: a 6 MV VMAT plan was optimized for PTV coverage, while a gamma knife technique was used to escalate dose to PGTV and PGTVLn. A comprehensive dosimetric comparison assessed the ability to simultaneously achieve boostvolume dose escalation and organsatrisk (OARs) sparing.
Results
TaiChi achieved comparable target conformity (CI: 0.87±0.05 vs. 0.86±0.04, p=0.239) but a steeper dose gradient (GI: 2.01±0.25 vs. 2.31±0.35, p<0.001). Significant dose escalation was observed with TaiChi for both PGTV (mean dose 80.58±1.52 Gy vs. 66.55±2.01 Gy, p<0.001) and PGTVLn (80.98±1.82 Gy vs. 65.53±1.61 Gy, p<0.001). PTV mean dose was moderately higher with TaiChi (67.11±3.21 Gy vs. 64.27±2.38 Gy, p=0.02). OAR sparing was significantly improved, with reductions in dose to the lung, spinal cord, heart, and esophagus.
Conclusion
The synergistic Xray/γray approach of the TaiChi platform enables safe and significant dose escalation to PETdefined boost volumes while reducing exposure to OARs. This technique holds promise for improving tumor control and reducing toxicity in SCLC radiotherapy.