ESTRO 2024 - Abstract Book

S153

Brachytherapy - Breast

ESTRO 2024

0.33 in those without late complications compared to 0.37. The optimal cut-point value for CTV was 39cc, 15cc for V150, 5cc for V200 and 0.38 for DNR.

Oncological outcomes revealed a 5-year overall survival rate of 95% and favourable rates for 3 rd IBTE-free survival (96%), regional relapse-free survival (100%), cancer-specific survival (98%), and distant metastatic disease-free survival (95%). Patients with V100 less than 97% showed increased risk of relapse (p = 0.01).

Conclusion:

CT for 2 nd IBTE shows favourable oncological outcomes and survival rates. Larger CTV, in addition to larger absolute volumes of V100, V150 and V200 were associated with increased risk of late toxicity. Treatment plans with more needles and lower DNR were associated with less complications, emphasizing the need for careful treatment planning and optimization in MIB based APBrI. Guidelines for dosimetry in 2 nd IBTE should be established to ensure optimal oncological and toxicity outcomes for patients seeking breast conservation. This study provides valuable insights for clinicians in risk stratification and treatment optimisation for CT in 2 nd IBTE, and supports the use of CT in this setting as an option for breast preservation.

Keywords: salvage, late, toxicity

References:

1. Walstra C, Schipper RJ, Poodt IGM, van Riet YE, Voogd AC, van der Sangen MJC, et al. Repeat breast-conserving therapy for ipsilateral breast cancer recurrence: A systematic review. Eur J Surg Oncol. 2019;45(8):1317-27.

1273

Mini-Oral

APBI with multicatheter high-dose-rate brachytherapy: 25-year results of a phase 2 clinical trial

Csaba Polgar 1,2 , Tibor Major 1,2 , Zoltan Takacsi-Nagy 1,2 , Janos Fodor 1

1 National Institute of Oncology, Center of Radiotherapy, Budapest, Hungary. 2 Semmelweis University, Department of Oncology, Budapest, Hungary

Purpose/Objective:

To report the 25-year updated results of accelerated partial breast irradiation (APBI) using multicatheter interstitial high-dose-rate (HDR) brachytherapy (BT).

Material/Methods:

Forty-five prospectively selected patients with T1N0-N1mi, nonlobular breast cancer without the presence of an extensive intraductal component and with negative surgical margins were treated with APBI after breast conserving surgery (BCS) using interstitial HDR BT. A total dose of 30.3 Gy (n=8) and 36.4 Gy (n=37) in seven