ESTRO 2025 - Abstract Book

S2728

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

ESTRO 2025

2. Grefve J , et al. Histopathology-validated gross tumor volume delineations of intraprostatic lesions using PSMA positron emission tomography/multiparametric magnetic resonance imaging. Physics and Imaging in Radiation Oncology 31 , 100633 (2024).

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Digital Poster Clinical Study of VMAT vs. 3DCRT for Breast Cancer with Lymph Node Involvement: Better Coverage, Faster Treatment, and No Increased Organ Dose Karina Lindberg Gottlieb 1 , Kenni Højsgaard Engstrøm 1 , Irene Hazell 1 , Lars Johnsen 1 , Martin Kjellgren 1 , Mette Holck Nielsen 2 , Carsten Brink 1 , Ebbe Laugaard Lorenzen 1 1 Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense, Denmark. 2 Department of Oncology, Odense University Hospital, Odense, Denmark Purpose/Objective: Coverage of lymph node regions in breast cancer radiotherapy, especially internal mammary nodes (IMN), is critical given emerging clinical evidence [1]. Volumetric Modulated Arc Therapy (VMAT) has been shown in planning studies to offer advantages over 3D Conformal Radiotherapy (3DCRT) in breast cancer treatment involving lymph nodes including IMN [2]. Several studies have however also shown an increased low-dose bath to both contra and ipsi lateral organs with VMAT. In spite of these planning studies, there is very limited clinical data directly comparing VMAT with 3DCRT. This study aims to assess clinical data, including target coverage, treatment time, and dose to organs at risk (OARs) in patients treated with either technique. Material/Methods: In a clinical study, VMAT was introduced for locoregional breast cancer radiotherapy, including IMN, at our institution on June 2023, following a pilot study [2]. The study included 203 patients: 105 received 3DCRT (June 2022 May 2023) and 98 received VMAT (June 2023-May 2024). Of these, 175 were treated with gating (92 in the 3DCRT group and 83 in the VMAT group). Target volume and OAR contouring followed ESTRO guidelines [3]. All patients underwent daily IGRT with CBCT, and plans were recalculated if external contour variations exceeded 8 mm. Treatment planning was done using Pinnacle with auto-planning, using a skin-flash of 10mm and Elekta linacs were used for delivery. Treatment times, recorded in the MOSAIQ system, were measured from beam-on to beam-off. All patients received 40 Gy in 15 fractions, with three in the 3DCRT group and four patients in the VMAT group receiving a simultaneous integrated boost. The 3DCRT utilized a tangential field-in-field technique, while VMAT used a "butterfly" technique with two arcs (Figure 1).