Abstract
PURPOSE: Leveraging the distinct properties of X-rays and γ-rays, a novel radiation therapy platform integrating both modalities has been implemented in clinical practice (NMPA: 20223050973; FDA: K210921). This study investigates the application of this integrated approach in spatially fractionated radiotherapy, systematically evaluating its feasibility and therapeutic potential. METHODS: In this retrospective study, lattice radiotherapy (LRT) was designed for 10 NSCLC cases with gross tumor volumes (GTV) ranging from 572 to 1367 cm³ (mean 862.9 ± 285.4 cm³), incorporating the number of high-dose vertices per case ranged from 6 to 13, with a median of 8.5, respectively. Each LRT plan consisted of a single 12 Gy dose to the intratumoral vertices, followed by conventional external beam radiotherapy (cEBRT) delivering 25 daily fractions of 1.8 Gy to the Planning Target Volume (PTV). Treatment plans were developed using the Varian Eclipse 13.5 Treatment Planning System (TPS) for Linac plans, while TaiChiB system plans were generated using the RT PRO TPS: a focused gamma plan was created to target the vertices, and a Linac plan was optimized to cover the PTV. A comparative analysis of D0.5 cc, D10/D90, EQD2, and Dmean was performed to evaluate the ability of dual-modality to optimize high-dose vertices while reducing doses to GTV margins and organs at risk (OARs). RESULTS: The LRT plan involved the placement of a median of 8.5 high-dose vertices (range, 6 to13), each with a diameter of 1.5 cm and spaced 3-3.5 cm apart within the GTV. The average vertices volume was 17.2 ± 4.5 cm³, corresponding to 2.05% ± 0.34% of the GTV. Compared to the Linac plans, the TaiChiB system plans demonstrated significantly increased D0.5 cc, Dmean, and EQD2 within the GTV (P < 0.01), improved peak/valley dose ratio (PVDR, D10/D90, P < 0.01), and reduced marginal GTV dose. Additionally, the TaiChiB system plans significantly reduced doses to OARs, including right lung Dmean (P = 0.031), heart Dmean (P = 0.024), esophagus Dmax (P < 0.01), and spinal cord Dmax (P = 0.042). All plans complied with the OARs dose constraints, thereby ensuring clinical feasibility and patient safety. CONCLUSION: By integrating X-ray and γ-ray technologies, this platform enhances the vertex dose within the GTV while reducing doses to the GTV margins and OARs, offering a promising and feasible approach for the treatment of LRT in patients with large-volume lung tumors.