BP10 Presentation Time: 5:21 PM

Abstract

Purpose

Accelerated partial breast irradiation (APBI) with multicatheter technique is a standard treatment in patients with low-risk breast cancer. In our institution it has been performed perioperatively for the last 10 years. We report our experience and results with this technique, with the different treatment schemes used as a result of the evidence available at the time.

Materials and Methods

Data from patients treated with APBI with perioperative HDR brachytherapy were evaluated. Inclusion criteria were: age ≥ 50 years, tumor size ≤3 cm, cN0, no evidence of distant metastases, hormone sensitive invasive tumors, her2 negative, ki67<25% and negative margins after lumpectomy. In situ tumors < 25 mm were eligible. Patients with tumors close to the skin (≤5mm), a known BRCA mutation, linfovascular invasion, extensive intraductal carcinoma, or multifocal disease were not included. All cases were presented to a multidisciplinary committee and evaluated by a radiation oncologist prior to surgery, and all patients had a pre-surgical functional imaging test (MRI or contrast enhaced spectral mammography). The tumor bed was marked with radiopaque markers. Catheters were implanted intraoperatively using a freehand technique after the pathologist ruled out axillary involvement and confirmed negative margins. Forty-eight hours after surgery, a CT scan and 3D planning were performed and a final pathology report was obtained. The fractionation used was either 34 Gy in 10 fractions, 30.1 Gy in 7 fractions, or 22.35 Gy in 3 fractions. Clinical and dosimetric data were collected (acute and late toxicity according to CTCAE, cosmetic assessment with De Wazer scale). Data were collected retrospectively in patients treated with 10 and 7 fractions and prospectively in patients treated with the ultra-accelerated technique.

Results

Between 2014 and 2024, 169 implants were evaluated in 166 patients. The median follow-up was 20 months. Patient, tumor and implant characteristics are shown in Table 1. Ipsilateral recurrence has been reported in one patient at 47 months post-treatment, and disease-free and cancer-specific survival rates were 99.4% and 100%, respectively. There were no acute or late grade 3 or greater toxicities. Acute and late grade 1-2 toxicities were observed in 9.6% and 10.8% of patients, respectively.

Conclusions

Perioperative accelerated partial breast irradiation using the multicatheter technique is a safe and time-efficient treatment option for selected patients. Long-term tumor control results will be reported with further follow-up. Because toxicity data were collected retrospectively in some patients and prospectively in others, toxicity rates have not been compared; however, overall data are favorable with approximately 10% grade 1 and 2 toxicity rates.