ESTRO 2024 - Abstract Book

S462

Clinical - Breast

ESTRO 2024

Results:

The relative difference of D 95 in the PTV high-dose area and the PTV low-dose area using synthetic CT are up to 1.64% and 6.74%. The relative difference of the Dmax of heart and spinal cord, esophagus, and contralateral breast were up to 6.25%, 4.95%, 4.13%, and 6.98%, and the relative difference of D mean , Dmax , V 5 and V 10 of ipsilateral lung were up to 1.82%, 3.21%, 0%and 0%, respectively.

Conclusion:

The method presented in this paper to generate composite CT images from CBCT scans taken during each treatment session suggests that a quantitative dose difference index useful for determining the timing of adaptive treatment can be rapidly and conveniently assessed. The results of this study are believed to provide a reliable basis for recognizing dose-volume histogram factors and adjusting patient treatment plans in the context of inter fractional treatment evaluation and adaptive radiotherapy. Future studies will attempt to establish standards in larger numbers of patients and explore other areas, such as the head, neck, and abdomen, where prominent anatomical changes make the role of adaptive radiotherapy important.

Keywords: Synthetic CT, Adaptive therapy

286

Digital Poster

Internal mammary node irradiation using arc technique in patients with node-positive breast cancer

Yu-Hsuan Chuang 1 , Pei-Yu Hou 1 , Pei-Wei Shueng 1,2 , Chen-Hsi Hsieh 1,2 , Chen-Xiong Hsu 1 , Deng- Yu Kuo 1 , Yueh-Feng Lu 1 1 Far Eastern Memorial Hospital, Department of Radiation Oncology, New Taipei City, Taiwan. 2 National Yang Ming Chiao Tung University,, School of Medicine, Taipei, Taiwan

Purpose/Objective:

Despite prospering development of treatment in breast cancer, internal mammary node irradiation (IMNI) remains a controversial subject with yet well-defined guidelines compared to other regional nodal irradiation (RNI) following MA.20 criteria. Upon reviewing the treatment plans established in the past 15 years, usage of arc devices with heart sparing techniques provided favorable target volume coverage under recommended OAR constraints. We therefore aim to evaluate the survival benefits of IMNI using arc-based radiation therapy in node-positive breast cancer patients and identify factors that may support clinical decision making.

Material/Methods: