ESTRO 2024 - Abstract Book

S3672

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

ESTRO 2024

Figure 2: Correlation of ΔCI and ΔBD (bridging dose) with distance to isocenter, geometric depth and distance to closest metastase.

Conclusion:

Adding the option for a VMAT optimization may be a promising approach to counter some of the more challenging situations (e.g. small distance between metastases) when treating patients with multiple lesions. Nevertheless, this work shows that there are also plans that can be improved by using DCA (e.g. for very small or nearly round shaped lesions). The development of a prediction model allows us to anticipate in advance which planning strategy (DCA or VMAT) will yield the best results. This can be further automated and refined in the future, paving the way for the development of a model-based approach built upon it.

Keywords: SRS, VMAT, prediction model

2481

Digital Poster

Subcentimetric Lung Metastases and Stereotactic Body Radiotherapy: Analysis and Clinical Outcomes

Santiago Velázquez 1 , Isabela Gaztelu-Blanco 2 , Sara Estrella-Marquez 2 , Maria Gonzalez-Vizuete 1 , Elena Montero Perea 3 1 HUVR, Medical Physics Departament, Sevilla, Spain. 2 HUVR, Radiotherapy Departament, Sevilla, Spain. 3 HUVR, Radiotherapy Departament, Sevilla, Spain

Purpose/Objective:

Subcentimetric lung metastases, defined as tumors smaller than the maximum range of 6MV radiation beams in the tissue-to-tumor rebuild-up region, present a unique challenge in radiation therapy. These tumors lack electronic equilibrium, making accurate dose calculation and verification difficult. Furthermore, their limited visibility on cone-beam computed tomography (CBCT) complicates image guide radiotherapy (IGRT). When the Gross Target Volume (GTV) closely resembles the Multi-Leaf Collimator (MLC) width, the risk of interplay effects is heightened. As a result, the development of a specialized treatment approach for Subcentimetric Lung Metastases is imperative. This study aims to address these challenges.

Material/Methods:

Thirteen patients with Subcentimetric Lung Metastases underwent Stereotactic Body Radiotherapy (SBRT). Treatment schemes varied based on topographical criteria such as M. Scorsetti and F. Alongi (1). All patients had a performance status of 0-2. Immobilization was achieved using the ExaCradle multidampening stereotactic system (Anatge) and the MoldCareBR-3 (ALCARE CO., Ltd). Dose calculations were carried out using Eclipse version 16.1 Acuros XB, and treatments were administered with a TrueBeam linear accelerator equipped with 5mm MLC.