ESTRO 2024 - Abstract Book

S4251

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

ESTRO 2024

Keywords: Rectum motion, Pelvic radiotherapy

References:

1. Nijkamp, J., et al., Target volume shape variation during irradiation of rectal cancer patients in supine position: comparison with prone position. Radiother Oncol, 2009. 93(2): p. 285-92.

2. Chong, I., et al., Quantification of organ motion during chemoradiotherapy of rectal cancer using cone-beam computed tomography. Int J Radiat Oncol Biol Phys, 2011. 81(4): p. e431-8.

3. de Jong, R., et al., Feasibility of Conebeam CT-based online adaptive radiotherapy for neoadjuvant treatment of rectal cancer. Radiation Oncology, 2021. 16(1): p. 136.

1356

Digital Poster

Population-based PTV for rectal boost radiotherapy: non-adaptive versus online-adaptive strategies.

Julien Pierrard 1,2 , Edmond Sterpin 1,3 , David Dechambre 2 , Geneviève Van Ooteghem 2,1

1 UCLouvain, Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Brussels, Belgium. 2 Cliniques Universitaires Saint-Luc, Department of Radiation Oncology, Brussels, Belgium. 3 KU Leuven, Laboratory of Experimental Radiotherapy, Leuven, Belgium

Purpose/Objective:

A radiotherapy boost to the primary tumour can be considered for long-course radiochemotherapy for the treatment of locally advanced rectal cancer [1]. Cone-beam computed tomography (CBCT)-guided online-adaptive RT (ART) has the potential to reduce the planning target volume (PTV) margin in this setting [2]. We computed a population-based PTV for the non-adaptive RT and compared it with that calculated for CBCT-guided online-ART to assess ART potential benefits.

Material/Methods:

We prospectively included 11 patients treated by rectal RT. Three CBCTs per RT session were acquired during the five first treatment days and, then, at the first session of each following week (total = 285 CBCTs). The GTVboost volume was defined as the circumferential rectal wall of the rectum involved by the tumour.