ESTRO 36 Abstract Book

S610 ESTRO 36 2017 _______________________________________________________________________________________________

hormone receptor (HR) negative patients was higher than HR positive (51.4 % vs. 27.5 %, p = 0.018). Conclusion The breast cancer molecular subtype is an important prognostic factor in BCBM. The patients with infra- tentorial metastases, radiation dose of less than 40Gy or no systemic treatment after WBRT are associated with worse OS. Patients with HR negative disease were more likely to develop intracranial progress. Those with less favorable prognosis according to Breast-GPA may benefit from the upfront WBRT. EP-1127 Dose to hippocampus in brain metastases radiosurgery: need for an hippocampal sparing approach S. Scoccianti 1 , D. Greto 1 , S. Calusi 2 , L. Poggesi 1 , C. Arilli 2 , M. Casati 2 , A. Compagnucci 2 , C. Becherini 1 , G.A. Carta 1 , I. Desideri 1 , M. Baki 1 , L. Visani 1 , G. Simontacchi 1 , P. Bonomo 1 , L. Bordi 3 , P. Bono 3 , S. Pallotta 2 , L. Livi 1 1 Azienda Ospedaliera Universitaria Careggi, Radiotherapy Unit, Florence, Italy 2 Azienda Ospedaliera Universitaria Careggi, Medical Physics Unit, Florence, Italy 3 Azienda Ospedaliera Universitaria Careggi, Neurosurgery Unit, Florence, Italy Purpose or Objective In recent years, on the basis of experimental and clinical evidence, some authors have suggested that neural stem cells in the gyrus dentatus of the hippocampus may be implicated as the main site of treatment-related cognitive deficits. Learning and memory impairment may be proportional to the volume of irradiated tissue in this location. Gondi et al (IJROBP 2013) suggested using very low dose constraints for the bilateral hippocampi volume (BHp) when patients are treated in conventional fractionation [dose to 40% of the BHp volume (D BHp40% )<7.3 Gy]. To date, dose constraints for hippocampus to be used in a single session are unknown. As far as they will be established, minimizing the dose is the only choice we can make. The aim of this study was to evaluate the dose received by hippocampus during Gammaknife Radiosurgery (GKRS) treatment for multiple brain metastases (BM) and to evaluate whether an Hippocampal Sparing approach could be useful. Material and Methods From 2013 to July 2015, 148 patients with BM were treated using GKRS. 20 plans of patients with ≥ 5 brain metastases were selected. In the 'real” plans for these patients, no attempt was made to spare the hippocampus. The plans were reviewed and, after contouring of BHp according to RTOG atlas, dose volume histograms for BHp were generated. Data regarding maximum, mean and D BHp40% were collected. Brain volume receiving 12 Gy (V12 brain ) was registered. All plans were replanned ('theoretical plans”) in order to minimize dose to BHp while maintaining equal target coverage. Results was <10cc in all plans. Distance from the hippocampus of each single lesion was the most important factor related to BHp dose. When this distance is >2 cm D BHp40% is negligible (<1.5 Gy). The size of lesions also affected the dose to BHp. Number of lesions do not have an impact on the BHp dose. Dosimetric parameters both for 'real” and 'theoretical” plans are listed in table 1. We observed a significant reduction of dose to BHp in optimized plans (i.e. 33% reduction in average D BHp40% ). Real Plan (Gy) Theoretical Plan (Gy) Max D BHp 5,57 (0,1-24,3) 3,12 (0,1-18,2) Min D BHp 0,6 (0-2,3) 0,41 (0-1,3) Mean D BHp 1,5 (0-5) 0,99 (0-3,4) Median BHp was 3,95 cc. V12 brain

D BHp40%

1,53 (0,03-5,1) 1,02 (0,03-3,7)

Conclusion Dose to BHp may be quite high during radiosurgery for brain metastases, especially in patients with lesions within 2 cm from the hippocampus. Since the hippocampus has been shown to be very radiosensitive also during a conventionally fractionated treatment, it is reasonable avoiding high single dose to this structure during a radiosurgical treatment. Thus, hippocampus needs to be included among the organs at risk during the planning process of radiosurgery, in order to be spared and to further minimize the risk of treatment-related neurocognitive impairment. Currently, in our institution, we are prospectively evaluating the neurocognitive impairment in patients treated with radiosurgery in order to find a relationship between dose and neurocognitive deficits. EP-1128 Stereotactic radiotherapy or whole brain with simultaneous integrated boost in brain metastases? F. Beghella Bartoli 1 , S. Chiesa 1 , C. Mazzarella 1 , S. Luzi 1 , R. Autorino 1 , S. Bracci 1 , F. Miccichè 1 , G.C. Mattiucci 1 , C. Masciocchi 1 , M. Massaccesi 1 , V. Valentini 1 , M. Balducci 1 1 Policlinico A.Gemelli, Radiation oncology department- Gemelli ART, Roma, Italy Purpose or Objective Brain metastasis (BMs) are frequently observed during oncological history. Treatment options include surgery, whole-brain radiotherapy (WBRT), stereotactic radiotherapy (SRT) or some combination of these. Despite multimodal treatment, prognosis remains severe. In this analysis we compared the SRT with WBRT plus simultaneous integrated boost (WBRT-SIB) in oligometastatic brain patients. Material and Methods From our database we selected oligometastatic patients affected by less than 3 brain metastases, with a primary tumor control, who underwent to SRT or WBRT-SIB. The SRT group received 850 cGy/die for 3 fractions, while the WBRT-SIB group received 300 cGy/die to the whole brain with a simultaneous integrated boost of 500 cGy/die to the BMs for 10 fractions. The two groups were matched for the following potential prognostic factors: age, gender, tumor type, number of brain metastasis and recursive partitioning analysis class (RPA). Local control (LC), overall survival (OS) and toxicity were evaluated. Results From 538 patients submitted consecutively to radiotherapy for brain metastases, 45 patients were eligible for this analysis. The groups were comparable in terms of sex, age, number of metastasis and RPA class. Median age was 63 years (range 38 – 87), 27 male and 18 female. Twenty-six patients (57.7%) underwent to SRT, nineteen (42.3%) to WBRT-SIB. The median number of brain metastases was 1 (range, 1-3). Acute toxicity (headache, hearing problems, nausea and vomiting), did not occur in treated patients. With a median follow-up of 20 months (range, 1.7 - 56 months), the median LC was not reached. The 1 year LC was 77% in all patients. The median and 1 year OS was 16 months 71%, respectively. No significant impact of treatment option on clinical outcomes was observed. Local control and OS data for each group are reported in table 1.