ESTRO 2025 - Abstract Book

S2863

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

3211

Proffered Paper Study of biologically guided lattice spatially fractionated radiation therapy based on diffusion-weighted imaging Ke Yuan 1 , Xinxiang Zhou 2,1 , Peng Xu 1 , Yiling Wang 1 , Zengyi Fang 2,1 , Meihua Chen 1 , Xianliang Wang 1 , Jinyi Lang 1 , Lucia Clara Orlandini 1 1 Department of Radiation Oncology, Radiation Oncology Key Laboratory of Sichuan Province, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China. 2 School of Medicine, University of Electronic Science and Technology of China, Chengdu, China Purpose/Objective: Lattice Radiotherapy (LRT) demonstrates efficacy in enhancing therapeutic effects while reducing toxicity; however, current LRT lattices are arranged in fixed geometric patterns without accounting for tumor heterogeneity. Parallelly, diffusion-weighted imaging (DWI) enables the derivation of apparent diffusion coefficient (ADC), and dose escalation to low-ADC regions (which represent high-density and proliferating) is proven to achieve lower biological toxicity and improved tumor control. However, there are currently no biologically guided strategies available for LRT. This study aims to design a lattice arrangement strategy and achieve biologically guided lattice radiotherapy (Bg-LRT).

Material/Methods:

This study included 10 patients with large chest tumors (TNM: T4 or N3). The ADC maps were derived from DWIs. Two steps of spherical filtering were applied to seek low-ADC voxels. A linear function incorporating ADC values and the minimum allowable spacing between lattice centers was established to avoid the decrease of the peak-to-valley dose ratio (PVDR) within the gross tumor volume (GTV). GTV lattice regions (GTV-Lattice) were generated from a predefined radius around the filtered voxels. Comparisons involved hexagonal close-packed LRT (HCP-LRT). Both methods prescribed a lattice dose of 60 Gy and a baseline GTV of 12 Gy, delivered over five fractions (Figure 1). The evaluation was based on the therapeutic ratio (TR) within the GTV (TR GTV ) and in subregions characterized by low ADC values (ADC10%-ADC50%). Additional metrics included PVDR within the GTV (PVDR GTV ) and the mean dose (Dmean) to organs at risk (OARs).