Abstract Book

S726

ESTRO 37

Results Between February 2009 and March 2017, 43 BC patients with 73 brain metastases were retrospectively reviewed. The histology of 49% of lesions was infiltrating ductal carcinoma. The most common molecular subtype was HER2 (54.5%), followed by LB (27.3%), TN (10.9%) and LA (7.3%). Patients with HER2 disease received HER2 antibodies or HER2/EGFR TKI. Among all patients, 63% received a course of cytotoxic chemotherapy after brain metastases diagnosis. The mean delivered dose was 36.76 Gy (range 12-45). 15 patients (34.8%) underwent whole brain RT (WBRT) prior or after stereotactic radiotherapy. No acute toxicities has been reported. At the first MRI, we recorded: complete response (CR) in 12.3%, partial response (PR) in 58.9%, stable disease (SD) in 28.8%. The response found at the last follow-up was: CR in 34.2%, PR in 30.1% and SD 16.4%; 19.2% of brain metastases presented progression. At a median follow-up of 9.8 months (range 1-70), the incidence of LF and RN was 13.7% and 8.2%, respectively. At the time of our analysis, 38 patients were alive. The median 1-year LF free survival rate was 89%; among molecular subtypes 1-year LF free survival rate was: LA 75%, LB 100%, Her2 87% and TN 100%. No difference in LF rate was observed according to molecular subtypes. Only the delivered dose (p=0.002) and WBRT (p=0.004) were predictive of local control. The median 1-year OS was 65.8%; among molecular subtypes 1-year OS rate was: 27.6, 27.5, 69.58, 8.4 in LA, LB, HER2 and TN, respectively. OS was significantly shorter in the TN cohort, instead of HER2 group probably due to targeted therapies. Conclusion SRT provides a good local control on brain metastases in patients affected by BC. In this analysis molecular subtypes are not predictive of response to SRT. EP-1326 Hypofractionated IMRT using Tomotherapy for early stage breast cancer: early chronic toxicity S. Dicuonzo 1 , S. Raimondi 2 , A. Surgo 3 , R. Spoto 3 , M. Gerardi 3 , A. Morra 3 , R. Ricotti 3 , V. Dell'acqua 3 , A. Casbarra 4 , S. Arculeo 4 , D. Rojas 4 , R. Luraschi 5 , F. Cattani 5 , C. Fodor 2 , P. Veronesi 6 , R. Orecchia 7 , M. Leonardi 3 , B. Jereczek 4 1 Dicuonzo Samantha, European Institute of Oncology, Milan, Italy 2 European Institute of Oncology, Department of Epidemiology and Biostatistics, milan, Italy 3 European Institute of Oncology, Department of Radiation Oncology, milan, Italy 4 European Institute of Oncology and University of Milan, Department of Radiation Oncology and Department of Oncology and Hemato-oncology, milan, Italy 5 European Institute of Oncology, Unit of Medical Physics, milan, Italy 6 European Institute of Oncology, Department of Surgery, milan, Italy 7 European Institute of Oncology and University of Milan, Department of Medical Imaging and Radiation Sciences and Department of Oncology and Hemato-oncology, milan, Italy Purpose or Objective to present two-years toxicity and cosmesis for breast cancer patients treated with a hypofractionated scheme including simultaneously integrated boost (SIB) using TomoDirect Material and Methods Two hundred and fifty women with Tis-T2 N0-N1 invasive breast cancer operated on conservatively were treated with hypofractionated scheme using TomoTherapy with Direct modality. Whole breast (WB) radiation and tumor bed (TB) were treated simultaneously to a dose of 45 Gy and 50 Gy, respectively, in twenty fractions over four weeks. Late toxicity was evaluated according to LENT/SOMA scale. Cosmesis was evaluated both by

limitations to the HF-RT studies such as the length of follow up, unclear heart toxicities due to short follow-up and combination with systemic treatment. To understand the patterns of care in German-speaking countries a survey was conducted regarding the use of normo- and hypofractionated radiotherapy techniques. Material and Methods Between July 2017 and August 2017, an email based survey was sent to all 1408 members of the German society of radiation oncology (DEGRO). The survey was completed by 180 physicians including 52 head of departments and 10 private practice owners. Results The majority of the 180 physicians who completed the survey use the normofractionated regimen of RT as standard treatment for early breast cancer (76.6%). Several physicians are sceptical about HF-RT and 7 physicians completely refused to use HF-RT. Many professionals do not agree (25.6%) on the new German guidelines suggesting HF-RT as standard treatment for all patients, or adopted a neutral position (32.8%) towards them. The main reasons for not aligning with the new guidelines are concerns about increased side effects and poorer treatment related outcome (Figure 1). Most physicians who perform HF-RT do so in an individual based manner (77.2%). Conclusion Although hypofractionation is more convenient for patients and less costly it remains controversial in German speaking countries. Our data shows that normofractionated RT remains the predominant method of treatment. However in a defined group of patients HF RT is widely used. Use of HF-RT seems safe and favourable in many cases. However most German physicians agree that particular patients, especially those at higher risk of RT late effects, may benefit from a less intense, extended fractionation schedule. EP-1325 Outcomes of stereotactic radiotherapy for brain metastases in different breast cancer subtypes S. Silipigni 1 , E. Ippolito 1 , A. Di Donato 1 , G. Petrianni 1 , C.G. Rinaldi 1 , B. Santo 1 , L. Trodella 1 , R.M. D'Angelillo 1 , S. Ramella 1 1 Campus Biomedico University, Radiotherapy, Roma, Italy Purpose or Objective To evaluate the response to stereotactic radiotherapy (SRT) among patients with brain metastases of different molecular subtypes of breast cancer (BC) treated with or without targeted therapies. Material and Methods Patients diagnosed with BC brain metastases were retrospectively evaluated. Molecular subtypes were defined as luminal A (LA), luminal B (LB), HER2 and triple negative (TN) based on the 2015 St. Gallen Consensus Criteria. For all patients stereotactic plans were generated using BrainLab's iPlan. Patients were treated using a thermoplastic mask. The primary outcome was local failure (LF), whereas secondary outcomes included overall survival (OS) and radiation necrosis (RN).