2267 - Dosimetric Advantage of Lattice Radiotherapy for Locally Advanced Bulky Head and Neck Cancer Using a Novel X-Ray and ?-Ray Combination Technique
Presenter(s)
Z. Wang, L. N. Zhao, W. Wang, Y. Gao, T. Zhang, Z. An, J. Duan, X. Sun, and L. Chen; Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China
Purpose/Objective(s): A novel radiotherapy platform integrating linear accelerator (linac) and gamma knife technologies has received clinical approval. This innovative system combines X-ray and ?-ray modalities to deliver a unique radiation therapy approach. This study aims to evaluate the dosimetric advantages of this hybrid technique for lattice radiotherapy (LRT) in patients with locally advanced bulky head and neck (H&N) cancer.
Materials/Methods: Retrospective treatment plans from three H&N cancer patients were analyzed, comparing conventional plans with combined X-ray/?-ray plans. The treatment strategy included two components: (1) an LRT plan delivering 15 Gy in a single fraction (15 Gy/1F) and (2) conventionally fractionated external beam radiation therapy (cERT). Conventional linac plans were generated using the treatment planning system (TPS) with volumetric-modulated arc therapy (VMAT), while combined plans were developed using the RT PRO TPS (OUR United Corp., Xi’an, China). The combined plans consisted of a gamma knife plan targeting high-dose vertices and a linac plan optimized for cERT. Dosimetric comparisons between conventional and combined plans were performed to assess the system’s ability to deliver high doses to vertices while minimizing dose to non-lattice target volumes within the gross tumor volume (GTV).
Results: The LRT plans included (8, 7, 10) high-dose vertices with a 1.2 cm diameter and 3–3.5 cm spacing within the GTV, respectively. Compared to conventional plans, the combined plans demonstrated significantly higher doses to vertices: D0.5cc (25.9 vs. 17.9, 25.1 vs. 18.9, 24.9 vs. 18.3 Gy), Dmean (20.1 vs. 16.4, 19.5 vs. 16.8, 19.9 vs. 16.7 Gy), and EQD2 (for D0.5cc, LRT plan: 77.5 vs. 41.6, 73.4 vs. 45.5, 72.4 vs. 43.2 Gy; total plan: 147.6 vs. 114.2, 141.5 vs. 115.2, 144.5 vs. 118.3 Gy). Additionally, the combined plans achieved lower doses to the GTV margin (3.6 vs. 4.8, 4.2 vs. 4.7, 4.0 vs. 4.9 Gy) and higher D10/D90 values for the GTV (5.6 vs. 2.4, 3.9 vs. 2.6, 5.5 vs. 3.0), demonstrating superior dose fall-off characteristics within the GTV. All organ-at-risk (OAR) dose constraints were met, confirming clinical feasibility.
Conclusion: The hybrid X-ray/?-ray radiotherapy platform leverages the complementary physical properties of both radiation modalities to achieve significant dosimetric advantages in LRT for locally advanced bulky H&N cancer. This technique enables precise delivery of high doses to vertices while maintaining steep dose gradients and sparing surrounding tissues, making it a promising treatment option for LRT in patients with locally advanced bulky H&N cancer. NMPA: 20223050973; FDA: K210921