ESTRO 2024 - Abstract Book

S4340

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

References:

[1 ] Bahadoer RR, Dijkstra EA, van Etten B, Marijnen CAM, Putter H, Kranenbarg EM, et al. RAPIDO collaborative investigators. Short-course radiotherapy followed by chemotherapy before total mesorectal excision (TME) versus preoperative chemoradiotherapy, TME, and optional adjuvant chemotherapy in locally advanced rectal cancer (RAPIDO): a randomised, open-label, phase 3 trial. Lancet Oncol 2021;22(1):29–42. https://doi.org/10.1016/S1470 2045(20)30555-6. [2]Valentini V, Gambacorta MA, Barbaro B, Chiloiro G, Coco C, Das P, Fanfani F, Joye I, Kachnic L, Maingon P, Marijnen C, Ngan S, Haustermans K. International consensus guidelines on Clinical Target Volume delineation in rectal cancer. Radiother Oncol. 2016 Aug;120(2):195-201. doi: 10.1016/j.radonc.2016.07.017. Epub 2016 Aug 12. PMID: 27528121. [3] Kavanagh BD, Pan CC, Dawson LA, Das SK, Li XA, Ten Haken RK, Miften M. Radiation dose-volume effects in the stomach and small bowel. Int J Radiat Oncol Biol Phys. 2010 Mar 1;76(3 Suppl):S101-7. doi: 10.1016/j.ijrobp.2009.05.071. PMID: 20171503.

2406

Digital Poster

A novel MR-guided treatment planning tool reduces accumulated critical organ dose in prostate cancer

Ellen H.A. Loeters 1 , Roel G.J. Kierkels 2

1 Radiotherapiegroep, Department of Radiation Oncology, Deventer/Arnhem, Netherlands. 2 Radiotherapiegroep, Department of Radiation Onology, Deventer/Arnhem, Netherlands

Purpose/Objective:

The 1.5 T MR-guided linear accelerator (MR-linac) has been designed and introduced to account for geometrical and anatomical changes throughout the radiation therapy treatment course. At each fraction, MR-guided adaptive radiotherapy is applied to assure target coverage and optimal organ at risk (OAR) sparing in the presence of these changes. Even though personalized radiotherapy requires adaptation to correct for accumulated over- or underdosage over fractions [1] , this is not part of the current clinical workflow. The aim of this study was to develop and evaluate a dose accumulation pipeline to estimate and compare the accumulated given dose (D Acc ) with the pre treatment planned dose for hypofractionated prostate cancer patients treated with the 1.5 T MR-Linac. In addition, we developed a novel, adaptive, treatment planning strategy as an alternative to the current clinical system.

Material/Methods:

The clinical treatment fractions of six palliative prostate cancer patients, treated with a prescribed dose of 35 Gy, 7 Gy in 5 fractions (2 weeks), were retrospectively evaluated using the dose accumulation pipeline. During each fraction, delineations of the clinical target volume (CTV) and the OARs within 2 cm from the target, were corrected on a T2-