ESTRO 2024 - Abstract Book

S460

Clinical - Breast

ESTRO 2024

grade 1-2 late toxicities (> 3 months) included fibrosis in 14 (41%), breast asymmetry in 12 (41%), and chest wall pain in 6 (18%).

Conclusion:

Repeat breast conservation utilizing a hyperfractionated partial breast RT regimen as defined by RTOG 1014 (45 Gy administered in 30 1.5 Gy twice-daily fractions) appears effective and well tolerated. No grade 3 or higher toxicities were observed, and local control was excellent. Longer-term follow-up among larger cohorts will define whether salvage mastectomy should remain the preferred standard.

Keywords: re-irradiation, breast conservation, salvage

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Digital Poster

Adaptive therapy dose evaluation study for breast cancer patients using synthetic CT

Bo Bae Lee 1 , Min Seok Cho 2 , Jun Young Son 2 , jeong heon kim 3 , Dong Hyeok Choi 3 , So Hyun Ahn 1,4 , Hwa Kyung Byun 2,5 , Kwang Woo Park 6,5 1 Ewha Womans University, Department of Medicine, Seoul, Korea, Republic of. 2 Yong-in Severance Hospital, Department of Radiation Oncology, Yong-in, Korea, Republic of. 3 Yonsei University College of Medicine, Department of Medicine, Seoul, Korea, Republic of. 4 Ewha Medical Research Institute, Ewha Womans University, Department of Medicine, Seoul, Korea, Republic of. 5 Yonsei University College of Medicine, Department of Radiation Oncology, Seoul, Korea, Republic of. 6 Yong-in Severance Hospital, Department of Radiation Oncology, Seoul, Korea, Republic of

Purpose/Objective:

The purpose of this study is to create a synthetic CT using cone beam CT and obtain quantitative indicators of dose in order to determine the timing of treatment plan modification for breast cancer patients receiving adaptive radiation therapy.

Material/Methods:

•The subjects are 20 breast cancer patients treated with Tangential volumetric modulated arc therapy technique at the Department of Radiation Oncology at Yong-in Severance Hospital from March 2020 to July 2023. The total number of fractionated irradiations is from a minimum of 15 to a maximum of 18, and the prescribed dose is 320 cGy at PTV high and 267 cGy at PTV low.