ESTRO 2025 - Abstract Book

S3345

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

ESTRO 2025

4144

Digital Poster Breast surface-guided-radiotherapy/image-guided-radiotherapy (SGRT/IGRT) during deep inspiration breath hold (DIBH):is what you plan what you deliver? Anna Delana 1 , Fiorenza De Rose 2 , Sara Lucidi 2 , Loris Menegotti 1 , Maria Andolina 2 , Laura Bandera 2 , Lucia Di Brina 2 , Patrizia Ferrazza 2 , Sergio Fersino 2 , Elena Magri 2 , Salvatore Mussari 2 , Dea Veshaj 2 , Francesco Ziglio 1 , Andrea Martignano 1 , Annalisa Trianni 1 , Valentina Vanoni 2 1 Medical Physics, APSS, Trento, Italy. 2 Radiation Oncology, APSS, Trento, Italy Purpose/Objective: To evaluate the impact of residual error on target coverage and dose delivered to Organs at Risk (OAR) during IGRT with surface guided DIBH. Material/Methods: Patients with early stage left breast cancer after conservative surgery underwent moderately hypofractionated whole breast irradiation (WBI). Radiotherapy was performed on an Elekta Versa linac as Volumetric Modulated Arc Therapy (VMAT) with the CRAD-Catalyst HD+ system for DIBH. Daily cone-beam CTs (CBCTs) were acquired and retrospectively analyzed: CBCTs were sent to the TPS (Elekta Monaco) and co-registered with the DIBH-CT in order to reproduce the patient positioning during the RT session. OAR contours (heart and ipsilateral lung) and the clinical target volume (CTV) were automatically adapted to the CBCT and evaluated by two experienced radiation oncologists and – if necessary – re-contoured on the CBCT. CBCT-Synthesized-CTs (SynCT) were created from daily CBCTs by assigning the mean densities retrieved from the planning CT for each region of interest (ROI), such as Body, Target and OARs to the respective adapted ROIs in the CBCT and the applied dose was re-calculated. PTV coverage and OAR doses calculated on the DIBH-CT and SynCTs were compared to verify the agreement between planned and delivered dose. PTV V95% (planning/delivery objective: > 98% ), mean heart dose (objective: < 4Gy), heart V17Gy (objective < 1 cc) and ipsilateral lung V17Gy (objective: < 25 %) were evaluated as dosimetric parameters. For one patient (Pt4), we accepted heart constraints that were higher (mean heart dose 5Gy and heart V17Gy 2cc) than our standard constraints as those could not be met due to her unfavorable anatomy.

Results:

Fig 1a