ESTRO 2025 - Abstract Book

S3628

Physics - Quality assurance and auditing

ESTRO 2025

[2] Van Esch A, Kulmala A, Rochford R, Kauppinen J, Harju A. Testing of an enhanced leaf model for improved dose calculation in a commercial treatment planning system. Med Phys. 2022 Dec;49(12):7754-7765. doi: 10.1002/mp.16019. Epub 2022 Oct 17. PMID: 36190516.

1904

Digital Poster Preliminary dosimetric assessment of Hippocampal Avoidance PCI in the EORTC-1901 PRIMALung Study Luiza F Souza 1 , Romaana Mir 2 , Sarah Kelly 1,3 , Raquel Bar-Deroma 4 , Enrico Clementel 1 , Coreen Corning 1 , Daniel Portik 1,5 , Aicha Traore-Diallo 6 , Antonin Levy 6 , Corinne Faivre-Finn 7 1 Medical, EORTC, Brussels, Belgium. 2 Department of Radiotherapy, Mount Vernon Cancer Centre, Northwood, United Kingdom. 3 Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium. 4 Department of Radiotherapy, Rambam Health Care Campus, Haifa, Israel. 5 Department of Radiation Oncology, GROW Research Institute for Oncology and Reproduction, Maastricht, Netherlands. 6 Department of Radiation Oncology, Gustave Roussy, Villejuif, France. 7 Department of Radiotherapy, Mount Vernon Cancer Centre, Manchester, United Kingdom Purpose/Objective: The PRIMALung Study (NCT04790253) aims to determine the overall survival (OS) of brain MRI surveillance versus brain MRI surveillance with prophylactic cranial irradiation (PCI) delivered with 25 Gy in 10 fractions for patients with limited or extensive-stage SCLC [1]. Investigators may deliver PCI with conventional or Hippocampal Avoidance (HA PCI) techniques [2]. Here we report preliminary radiotherapy quality assurance of HA-PCI and dosimetry of the target and peri-hippocampal region. Material/Methods: The first HA-PCI plan per site was evaluated by an expert EORTC reviewer. Data analyses were performed using Velocity Version 4.1 for 15 pseudonymised HA-PCI plans. The mandatory dose objectives included D98% ≥95% for PTV_2500 and D98% ≤ 8.5Gy, D0.03cc≤ 15.0Gy to the hippocampi. The peri-hippocampal region was assessed using two methods: 1) D0.03cc for each 1mm isotropic expansion beyond Hippocampi_PRV05 (combined, bilateral hippocampi with a 5mm isotropic margin) to Hippocampi_PRV10 [Figure 1(a)] [2]; and 2) minimum distance (mm) from the hippocampi to the 25Gy isoline [Figure 1(b)].

Figure 1 (a) 1mm expansion from Hippocampi_PRV05 (yellow) to Hippocampi_PRV10 (pink) (b) Minimum distance (mm), from the Hippocampi (blue) to the 25 Gy isodose line (red).

Results: The mean D98% to the PTV_2500 was 93.5% (23.39Gy). The mean D98% and D0.03cc for the hippocampal structures were 7.55Gy and 13.46Gy, respectively. Three plans exceeded the mandatory Hippocampi dose constraints. Two