S324
Clinical - Breast
ESTRO 2026
Purpose/Objective: Breast cancer (BC) is the second cause of brain metastases (BM), with a CNS involvement of about 12.6%.Standard treatment for BM-BC is ablative Stereotactic Radiotherapy (SRT), both in terms of single session radiosurgery (RS) or fractionated stereotactic radiotherapy (FSRT). The association of SRT with novel systemic treatments (ST) may have a synergistic effect but might also increase the risk of severe toxicity. This study aims to evaluate the efficacy and the toxicity profile in this setting. Material/Methods: Clinical and dosimetric data regarding BM-BC patients treated with SRT and concurrent ST (within 28 days) from 2018 to 2024 were collected in this multicenter retrospective study (Table1).
patients (n=139) had ≤ 4 brain lesions. Table2 reports dosimetric data.
The median time interval SRT-ST administration was 5 days (range 0-28). Local control and freedom from new BM rates were 69.94% and 40.13%, respectively. The median PFS was 18.5months (range 1-86), median OS was 26.5months (range 3-120). The median DIC- free survival and median EC-free survival were 14.9months (range 1-73) and 17.6months (range 0-90), respectively. The factors significantly associated with poor OS were median volume (cc) of the largest lesion (p=0.002) and median cumulative intracranial BM volume (cc) (p=0.002). These factors were also significantly associated with and poor local control with p=0.037 and p=0.017, respectively.G3- radionecrosis (RN) was reported in 6 patients (2 NabPaclitaxel-Atezolizumab, 1 Trastuzumab- Pertuzumab, 1 TDM-1, 1 CDK4/6i), whereas a case of G4-RN was histologically proven in a patient under TDM-1 treatment after 26.6 months. The median RN- free survival was 14.4 months. No other ≥ G3 toxicity was recorded. The factor significantly associated with G2/G3-RN was the median cumulative intracranial BM volume (cc) (p=0.04). Conclusion: The addition of novel ST results to improve the CNS- efficacy of the treatment. The association novel ST-SRT seems to be safe, with an RN incidence consistent with literature data referred to exclusive SRT. Keywords: Brain metastases, Breast cancer, Systemic therapy
Results: One hundred forty-sevenpatients, aged between 30 and 91 (mean age 75), for a total of 338 BM-BC, treated in 12 different Radiation Oncology Centers with SRT, were included. BM were diagnosed after a mean time interval of 5.4 years from the diagnosis of primary BC. Most patients (n=116) had previously received systemic therapy for metastatic BC. Estrogen receptors were positive in 58 patients, 72 patients were HER-2+; 17 patients had triple-negative BC. At BM diagnosis, 56.46% of patients had controlled extra- cranial disease, 91 patients had KPS ≥ 90, 102 patients had no neurological symptoms. The majority of
Digital Poster 4322 Positional Changes of Axillary
Contents:Implications for defining the residual axillary nodal basin for radiotherapy after ALND for breast cancer Jill T Nicholson 1,2 , Sinead Cleary 1 , Ciaran Malone 1,3 , Aisling Barry 4 , Sinead Brennan 1,5 , Orla McArdle 1,6 , Abeeda Butt 6 , Rebecca Geary 1 , Gurdeep Manu 7 ,
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