ESTRO 2024 - Abstract Book

S164

Brachytherapy - Breast

ESTRO 2024

Kazuhiko Sato (1), Hiromi Fuchikami (2), Naoko Takeda (3), Takahiro Shimo (4), Masahiro Kato (5), Tomohiko Okawa (6)(1) Department of Breast Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan, Japan,(2) Department of Breast Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan, Japan,(3) Department of Breast Oncology, Tokyo West Tokushukai Hospital, Tokyo, Japan, Japan,(4) Department of Radiation Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan, Japan,(5) Department of Radiation Oncology, Tokyo-West Tokushukai Hospital, Tokyo, Japan, Japan,(6) Preventive Medical Center, Sano City Hospital, Tochigi, Japan, Japan. https://doi.org/10.32768/abc.202182149-155

3149

Proffered Paper

The toxicity and value of interstitial brachytherapy boost for high-risk breast cancer patients

Hong Linh Ha, Nikola Cihoric, Marcela Blatti, Elena Riggenbach, Kristina Lössl

University Hospital of Bern, Radio-Oncology, Bern, Switzerland

Purpose/Objective:

Adjuvant whole breast irradiation (WBI) and additional boost dose to the former tumor bed improve local control (LC) of breast cancer patients in all age groups with boost dose prescriptions varying from 8-16Gy/4-8 fractions, whereas 16 Gy is recommended for patients with high-risk factors such as young age, extensive intraductal component (EIC), positive surgical margins and triple negativity (TN) [1,2,3,4,5,7,8,9]. Large external boost volumes double the likelihood of late toxicities and leads to poor cosmetic outcomes [1,4,5,6]. Our hypothesis is that multicatheter interstitial HDR brachytherapy (BT) boost in patients with local high-risk factors results in an equivalent LC rate and no increase in late side effects on organs at risks (OARs), such as skin, subcutaneous tissue and also heart and lung, compared to the common EBRT approach [1]. Clinical trials vaguely present a consensus on BT boost treatment of patients with breast cancer after WBI. Therefore, we retrospectively examined the value and outcome of multicatheter BT as an equivalent option of boost delivery providing a foundation for further prospective studies.

Material/Methods:

A monocentric observational study with high-risk breast cancer patients who received WBI and sequential BT boost (6x2.5Gy, twice daily) from 03/2006 to 10/2018 was performed in our tertiary cancer centre to evaluate our institutional experience. Patients receiving BT boost as a re-irradiation were excluded. Local control (LC) ) and overall survival (OS) rates were determined using the Kaplan–Meier estimator. Univariate log-rank tests were performed to test the impact of risk factors on the likelihood of ipsilateral local recurrence and a Cox proportional hazard model to explore significant factors. Toxicity results were determined according to Common Terminology Criteria for Adverse Events version 5 (CTCAE v.05). Statistical analyses were performed using SPSS Version 29.0.

Results: