ESTRO 2025 - Abstract Book

S2916

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

ESTRO 2025

References: WINKEL, Dennis, et al. Adaptive radiotherapy: the Elekta Unity MR-linac concept. Clinical and translational radiation oncology , 2019, 18: 54-59.

4062

Digital Poster Could proton pencil beam scanning arc therapy improve the sparing of circulating blood cells in Glioblastoma patients? Abdelkhalek Hammi 1 , Peilin Liu 2 , Sebastian Tattenberg 3,4 , Cong Xiaoda 2 , Xuanfeng Ding 2 1 Physics, TU Dortmund, Dortmund, Germany. 2 Department of Radiation Oncology, William Beaumont University Hospital, MI, USA. 3 Life Sciences Division, TRIUMF, Vancouver, Canada. 4 School of Natural Sciences, Laurentian University, Sudbury, Canada Purpose/Objective: Background: Radiation therapy reduces circulating lymphocytes (CL), the most radiation-sensitive cells, leading to radiation-induced lymphopenia, which is associated with poorer overall survival in glioblastoma patients [1]. Purpose: To compare the dosimetric impact of spot-scanning proton arc (SPArc) therapy versus standard intensity modulated proton therapy (IMPT) on CL dose and organ-at-risk (OAR) sparing in glioblastoma radiotherapy. Material/Methods: Ten glioblastoma cases were retrospectively analyzed. For each case, a cerebrovascular model was developed (Fig a b), along with a cardiovascular model to simulate the continuous blood flow through the brain and entire body during radiation delivery [2]. The circulatory system, comprising 32 organs, was based on hemodynamic data from ICRP Publication 89 [3]. Treatment planning included IMPT and alternative SPArc plans, each delivering a total dose of 50 Gy in 2 Gy fractions. A dynamic beam delivery model simulated the spatially varying instantaneous dose rates within the patient, based on a published machine-specific delivery system controller from Beaumont Proton Therapy Center with upstream and downstream energy-layer-switching times of 5s and 0.7s, respectively. Dosimetric comparisons included V30 for the brainstem and chiasm, CL exposure volume V >0Gy , the D 2% index (maximum dose to the last 2% blood volume), and the fraction of CL depleted post-treatment.