ESTRO 2025 - Abstract Book

S4389

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

3742

Proffered Paper Reduced Heart and Lung dose of Rapid Arc Dynamic versus IMRT Holds Potential for Toxicity Reduction for Esophageal Cancer Pieter Populaire 1,2 , Karel Aerts 1 , Truus Reynders 1 , Wout Piot 1 , Bianca Vanstraelen 1 , Karin Haustermans 1,2 , Wouter Crijns 1,2 1 Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium. 2 Department of Oncology, KU Leuven, Leuven, Belgium Purpose/Objective: Patients with esophageal cancer (EC) that undergo neoadjuvant chemoradiotherapy followed by surgery are at risk for developing multiple complications. Mean lung dose (MLD) has previously been associated with increased risk for postoperative pulmonary complications (PPCs), shaping NTCP models. Therefore, treatment planning should aim to reduce MLD, warranting technological advances such as Rapid Arc Dynamic (RAD) (Varian), which leverages both the advantages of intensity modulated radiotherapy (IMRT) and Volumetric Arc Therapy while also allowing collimator rotation. Here, we compared dose and NTCP of clinical IMRT-plans versus RAD-plans. Material/Methods: Ten EC-patients (7 adenocarcinoma, 3 squamous cell carcinoma) that underwent clinical planning with IMRT were selected based for comparative planning with RAD. Dose prescription was 50.4Gy in 28 fractions, using a PTV margin of 7mm (relevant clinical goals displayed in Table 1). Clinical IMRT-plans were developed with a class solution for Halcyon (Varian), with fixed beam angles at 220 ◦ , 300 ◦ , 330 ◦ , 0 ◦ , 30 ◦ , 60 ◦ , 155 ◦ and calculated with ACUROS, photon optimizer 16.1. RAD-plans were designed as one arc, 5 static ports (205 ◦ ,330 ◦ ,0 ◦ ,30 ◦ ,155 ◦ ), free TPS-based collimator optimisation and balanced preference between arc section and static ports (26 control points per static port). Calculation was performed using ACUROS, photon optimizer 18.1. Clinical goals were compared between IMRT and RAD using two-sided paired t-tests. Corresponding NTCP for PPCs (Thomas et al. [1]) of IMRT was compared to RAD. Results: RAD-plans yielded lower doses of all clinical goals of heart and lungs when compared to IMRT plans (Figure 1, Table 1). There was a modest increase (2.2 Gy) in SpinalCord_D 0.035cc when using RAD. On average the relative MLD decrease of the RAD-plan was 20.2% (SD: 6.3%). Corresponding NTCP was on average 33.5% for the IMRT-plan and 26.0% for the RAD-plan, resulting in an average ΔNTCP of 7.5% (SD: 4.9%).