ESTRO 2024 - Abstract Book

S159

Brachytherapy - Breast

ESTRO 2024

but remain visible only in 12.3% at long term, and is considered skin G1 toxicity. Fibrosis or slight induration in the surgical bed (G1) was reported in 22% (n=18) and was considered moderate (G2) in 7 cases (9%). No case of telangiectasia has been described. Cosmetic outcome is considered good or excellent in 95% and fair in 5%. Several cases of asymptomatic fat necrosis can be seen in the mammograms at 4-5 years but without influence on the cosmesis. No relationship has been found between the cases of fibrosis or fat necrosis and dosimetry.

Conclusion:

VAPBI with MIBT using four fractions of 6.25Gy or three fractions of 7.45Gy in two or three days gets good local control as 7-8 fractions, with the same acute effects. Late effects show a small increase of fibrosis G2 at five years (8.6%), similar to GEC ESTRO phase III trial. VAPBI in two days can be a good choice to decrease the total time of treatment, which is beneficial for the patient and to reduce the workload.

Keywords: APBI, HDR, brachytherapy

2838

Digital Poster

Clinical accuracy evaluation of electromagnetic tracking enabled implant reconstruction in breast BT

Christopher Dürrbeck 1,2,3 , Birte Christina Sauer 1,2 , Michael Lotter 1,2 , Stephan Kreppner 1,2 , Rainer Fietkau 1,2 , Vratislav Strnad 1,2 , Christoph Bert 1,2,3 1 Universitätsklinikum Erlangen, Department of Radiation Oncology, Erlangen, Germany. 2 Universitätsklinikum Erlangen, Comprehensive Cancer Center, Erlangen, Germany. 3 Friedrich-Alexander-Universität Erlangen Nürnberg, Lehrstuhl für Strahlentherapie, Erlangen, Germany

Purpose/Objective:

Implant reconstruction in interstitial breast brachytherapy is time-consuming and associated with the risk of systematic human error. In view of the growing trend towards ultra-short fractionation schemes [1-3], reliable, accurate, and fast catheter implant reconstruction will become more important. Streamlining the reconstruction procedure through automation is key to an enhanced and more time-efficient treatment planning. In this study, we present an innovative approach to increase the accuracy and reduce the time required for implant reconstruction in interstitial breast brachytherapy by means of an electromagnetic tracking (EMT) system integrated into an afterloader.

Material/Methods:

An EMT-enabled prototype afterloader (Flexitron, Elekta Brachytherapy, Veenendaal, The Netherlands), whose check cable was fitted with an EMT sensor, was used to assess the geometry of the catheter implants of 72 patients, which together comprised more than 1200 catheters. The implant geometry was recorded immediately after the planning CT scan, while the patient was still lying on the CT couch. The EMT implant data were processed to remove breathing motion artefacts and were rigidly registered to the reference frame of the CT image using