S12
Track-Topic
ESTRO 2026
to establish the role of adjuvant multicatheter interstitial high-dose-rate brachytherapy (HDR-BT) in a doubly accelerated and radiobiologically equivalent irradiation scheme of 5 x 5,4 Gy delivered in 3 days of treatment (High Five, HiFi-APBI) compared to a 4-5-day standard in selected women with low-risk invasive breast cancer or DCIS. This report presents 2-year toxicity profiles, cosmetic outcome results, and local control data. Material/Methods: Early low-risk breast cancer patients (pTis-2N0) were recruited between October 2021 and December 2023. Postoperative adjuvant treatment with interstitial HDR-BT was administered on an outpatient basis over three days (5 x 5.4 Gy, 6 hours apart; total 27.0 Gy). Follow-up (FU) was continued for one month post- treatment, then at three-month intervals up to 2 years, and at six-month intervals up to 5 years. At 2 years, the incidence of late toxicity (skin, subcutaneous tissue) was assessed according to RTOG scales, as well as Harvard scale-based cosmetic outcomes and patients’ feedback based on a four-grade subjective breast appearance scale (excellent, good, satisfactory, poor). Regular photographic documentation, control mammography, and ultrasonography findings were secured. Results: 147 women aged 65 (51-85) were enrolled. At the time of analysis (October 2025), patients reached 30,9 months FU (range 1,2-46,1), and 128 (87,1%) reached full 2-year FU by protocol (two patients withdrew consent, one died of comorbidities 20 months post treatment). Late toxicity at 2-year FU: RTOG skin G0 – 124 (96.9%), G1 – 4 (3.1%); RTOG subcutaneous tissue G0 – 125 (97.7%), G1 – 2 (1.5%), G2 – 1 (0.8%) [Fig.1]. Asymptomatic fatty tissue necrosis (mostly single 5-20 mm foci) identified on mammograms or ultrasound occurred in 13 (10.2%) and 29 (22.87%) cases, respectively. Patients subjectively assessed their cosmetic outcome after two years post-treatment as excellent (73.4%), good (22.7%), satisfying (3.1%), and poor (0.8%). Clinicians assessed cosmesis (Harvard scale) after two years as grade I (excellent; 45.3%), II (good; 50.8%), III (satisfactory; 3.1%), and IV (poor; 0.8%) [Fig. 2]. Two-year local control was 100%, and disease-free survival was 97.7% (two patients developed new primaries in the contralateral breast, and one patient developed a new primary in another quadrant).
Conclusion: The incidence of 2-year late toxicity was extremely low. Subjectively (patient-based) and objectively (Harvard scale) assessed cosmesis was predominantly excellent/good. Two-year local control was 100%. In the analysis, the HiFi-APBI regimen appeared to be highly effective and well-tolerated, particularly in terms of patient compliance, late toxicity, and cosmesis. Keywords: High Five APBI, late toxicity, cosmesis Mini-Oral 3016 Dosimetric evaluation of the perioperative concept in interstitial HDR breast brachytherapy Georgina Fröhlich 1,2 , Zsófia Mészáros 2 , Viktor Smanykó 1 , Norbert Mészáros 1 , Tibor Major 1,3 , Zoltán Takácsi-Nagy 1,3 1 Centre of Radiotherapy, National Institute of Oncology, Budapest, Hungary. 2 Department of Biophysics, Eötvös Loránd University, Budapest, Hungary. 3 Department of Radiotherapy, Semmelweis University, Budapest, Hungary Purpose/Objective: To investigate the dosimetric impact of perioperative concept in interstitial high-dose-rate second breast- conserving brachytherapy (BT). Material/Methods: Treatment plans of the consecutive 30 postoperative and 30 perioperative interstitial breast-conserving BT were selected. The postoperative implantation is based on a preimplant CT, and planning of the catheter positions in the template is guided by the contoured target volume. During perioperative BT, the surgical margin around the lumpectomy cavity is only
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