ESTRO 2025 - Abstract Book

S2936

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

ESTRO 2025

In our center a different approach, called Mixed Technique (MT), which combines conformational fields with VMAT, using two fixed fields and one arc, is employed. This approach leverages the advantages of both techniques. The aim of this study is to compare the MT with VMAT and IMRT in terms of dosimetric outcomes and treatment time. Material/Methods: Ten patients with left breast cancer treated using the breath-hold (BH) technique were included. Treatment plans involved a total dose of 40.5Gy\15fz, (48Gy\15fz with simultaneous boost). Each patient was planned using the MT and subsequently replanned using VMAT and IMRT. Metrics assessed included dose to organs at risk (OARs) — heart, left anterior descending artery (LAD), lungs, and contralateral breast — as well as planning target volume (PTV) coverage, homogeneity index (HI), conformity index (CI) and delivered monitor units (MU). Results: Analyzing DVH’s data with paired T-tests, significant dose reduction (p<0.05) was found in D1% of contralateral breast (38.46% reduction compared to VMAT and 37.69% reduction compared to IMRT), V5Gy of ipsilateral lung (12.26% reduction compared to VMAT) and contralateral lung (100% reduction with both VMAT and IMRT). Regarding the heart, there is a reduction in mean dose (23.12% reduction compared to VMAT) and V5Gy (29.24% reduction compared to VMAT and 72.78% reduction compared to IMRT). In addition, a significant reduction in MU delivered was found (23.71% less than VMAT and 68.76% less than IMRT) implying shorter treatment length and significantly better coverage of PTV D95% (2.43% increase than VMAT and 2.23% than IMRT), D98% (4.23% increase regarding VMAT and 3.29%) and boost D98% (1.11% increase regarding VMAT and 2.45% regarding IMRT). There’s a decrease in HI for both PTV (16.76% decrease compared to VMAT and 20.75% decrease compared to IMRT) and boost (8.30% decrease compared to VMAT and 45.32% decrease compared to IMRT), while an average CI of 0.40 for MT versus 0.40 IMRT and 0.51 VMAT is found for PTV and a CI of 0.58 for MT versus 0.87 IMRT and 0.59 VMAT. Conclusion: The MT achieves significant dose reductions to OARs while maintaining excellent target coverage and dose homogeneity. Its efficiency in terms of MU and shorter treatment duration makes it particularly advantageous for breath-hold treatments. Further studies are planned to expand the patient cohort and validate these findings.

Keywords: Treatment planning, breast, dose reduction

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Digital Poster Radiotherapy treatment planning for brain metastases over 2016-2021 and reflections on future machine and software renewal. Tomas Kazda 1,2 , Katerina Polachova 1,2 , Tomas Prochazka 1,2 , Lucie Hnidakova 1,2 , Petr Pospisil 1,2 , Ludmila Hynkova 1,2 , Jana Maistryszinova 1,2 , Petr Burkon 1,2 , Marek Slavik 1,2 , Ivana Kolouskova 3,4 , Andrea Pagacova 5 , Sarka Kristkova 5 , Radek Minarik 1 , Jan Svancara 6 , Jan Garcic 1 , Pavel Slampa 1,2 1 Department of Radiation Oncology, Masaryk Memorial Cancer Institute, Brno, Czech Republic. 2 Department of Radiation Oncology, Faculty of Medicine, Masaryk University, Brno, Czech Republic. 3 Department of Comprehensive Cancer Care, Masaryk Memorial Cancer Institute, Brno, Czech Republic. 4 Department of Comprehensive Cancer C, Faculty of Medicine, Masaryk University, Brno, Czech Republic. 5 Faculty of Medicine, Masaryk University, Brno, Czech Republic. 6 Medical Information Unit, Masaryk Memorial Cancer Institute, Brno, Czech Republic