ESTRO 2025 - Abstract Book

S769

Clinical - CNS

ESTRO 2025

4526

Digital Poster Stereotactic Radiotherapy + Systemic therapy for brain metastases from breast cancer: preliminary results of a multicentric retrospective study Camilla Delli Paoli 1 , Lucia Pia Ciccone 1 , Paolo Matteucci 2 , Karol Migliorati 3 , Francesca Giugliano 4 , Alberto Franzin 3 , Cesare Guida 4 , Sara Ramella 5 , Silvia Scoccianti 1 1 Radiation Oncology Unit, Ospedale Santa Maria Annunziata, Azienda USL Toscana Centro, Florence, Italy. 2 Fondazione Policlinico Universitario, Campus Bio-Medico, Rome, Italy. 3 UO Neurochirurgia, Fondazione Poliambulanza, Brescia, Italy. 4 Reparto Radioterapia, Ospedale del mare, Naples, Italy. 5 Università Campus Bio Medico, Fondazione Policlinico Universitario Campus Bio-Medico, Rome, Italy Purpose/Objective: To evaluate efficacy and toxicity of stereotactic radiotherapy (SRT) and concomitant systemic therapy in patients with brain metastases (BM) from breast cancer (BC) Material/Methods: Clinical and dosimetric data regarding patients treated with SRT and concurrent systemic therapy (within 28 days) for BM from BC were retrospectively collected in a multicenter retrospective study. Results: Twenty-nine patients, aged between 37 and 83 (mean age 58,5) for a total of 77 BM, treated in 4 different Radiation Oncology Centers with SRT were included. BM were diagnosed after a mean time interval of 5,7 years from the diagnosis of primary breast cancer. Most patients (n=24) had previously received systemic therapy for metastatic breast cancer. Estrogen receptors were positive in 20 patients, while HER 2 + patients were 12; 7 patients had triple negative BC. At the diagnosis of brain metastases, 16 patients had controlled extra cranial disease, 18 patients had KPS ≥90, 22 patients had no neurological symptoms. The majority of patients (n=27) had ≤4 brain lesions. Eleven patients were treated with GammaKnife-Radiosurgery, while 18 received Linac-based-SRT. Nineteen received single session Radiosurgery (RS) for a median dose of 20 Gy (range 15-24), whereas ten patients were treated with hypofractionated SRT (HFSRT) (24 or 27 Gy in 3 #). Prescription isodose line ranged between 50 and 80%. Mean target volume was 3,24 (range 0,08-13,95 cc), whereas mean cumulative intracranial tumor volume was 4,68. For RS-patients median V12 was 1,79 and 1,60 if including or excluding GTV, respectively. For HFSRT-patients median V20 was 25.15 and 4,30 if including or excluding GTV, respectively. Five patients received SRT at the progression of BM, while 24 patients were treated with upfront-SRT. Systemic therapy consisted in the following agents: Trastuzumab Deruxtecan (n=4); Trastuzumab Pertuzumab (n=3); CDK4/6 inhibitors (n=3); TDM1 (n=2); Lapatinib (n=2); Tucatinib (n=2); other (n=13). Median time interval between SRT and administration of systemic therapy was 10 days, respectively (range 0-28). Local control and freedom from new brain metastases rates were 62% and 34,5%, respectively. Median localPFS, distantPFS and OS were 20,1, 17,4 and 23,5 months, respectively. One case of G3 radionecrosis was histologically proven for a patient treated with RS concomitant to TDM1 after 26,6 months. No other ≥G3 radiation-induced toxicity was registered Conclusion: SRT concomitant to systemic agents was shown to be an effective treatment against BM from BC without increasing the rate of severe radionecrosis

Keywords: Brain metastases, Breast cancer, Systemic therapy