ESTRO 38 Abstract book

S681 ESTRO 38

steroids. Two patients with good improvement post reRT developed intra-tumoral bleed on day 15 & 45 and succumbed. The post reRT 13 progression were noted where local and disseminated were 10 and 3 respectively. The median OS of the whole group was 15.3 m with OS at 12, 18 and 24 m of 81.6+9.6, 39.1+13.1 and 20.9+12% respectively. The median survival addition with reRT was 4.6 m (Fig 1, p<0.001). The median OS for patients receiving <30Gy versus 39.6-45Gy was 3.6 and 4.9 m respectively (p=0.14). The median OS for reRT responders vs non-responders was 4.9 vs 3.5 m (p=0.005, Fig 2).

Material and Methods We performed an IRB-approved retrospective analysis of patients underwent LINAC-based, image-guided, frameless FSRT consisting of 35Gy/5fractions for lesions 1- 15 cc and 30Gy/5 fractions for lesions 15cc< at our institution from August 2015 to August 2018. MRI were recorded at the initial time as a baseline and 2 months after the FSRT. Volumetric assessment of tumor regression and its relations to peritumoral edema were performed using contrast enhanced T1MRI, T2 weighted-MRI and perfusion- MRI. Results We have treated 32 patients with 104 multiple brain metastases ranging 2 to 14 metastases (median 5). Primary cancer sites were lung (27), breast (3), cervix (1), and kidney (1). The mean metastases volume decreased from 4.67 ± 5.22 cc to 2.54 ± 2.48 cc ( p = 0.001), and the mean edema volume decreased from 20.11 ± 20.23 cc to 11.35 ± 20.47 cc ( p = 0.02). Cumulative tumor volumes were 2.5- 39.6cc (median 22.4cc). The pre-existing edema was reduced in 78% (n=25), stable in 22% (n=7) at the time of first 2-months follow-up. Reduction of >75 % in existing edema was associated with the cumulative tumor volumes <10 cc ( p = 0.03) and primary adeno lung cancer ( p = 0.02). In 9/104 (8.6%) metastases, local failure was diagnosed with a mean follow-up time of 7.4 months (range 1-34 months). Estimated 1-year local control was 90.6%. Overall, 24/27 (88%) patients suffered from symptomatic edema was improved. No patients who were without symptoms at baseline developed signs of intracranial pressure following LINAC based FSRT. Conclusion LINAC based stereotactic radiotherapy for multiple metastatic brain lesions demonstrated a relatively safe and effective treatment outcome with early shrinkage of lesions and peri-tumoral edema. Further investigation is needed to clarify the optimal dose fractionations. EP-1237 Vestibular schwannoma: Results of hypofractionated stereotactic radiotherapy P. Pierre-Marie 1 , S. Tringali 2 , G. Beldjoudi 1 , P. Pommier 1 , R. Tanguy 1 1 Centre Léon Bérard, Radiotherapy, Lyon, France ; 2 Centre Hospitalier Lyon Sud, Head and Neck, Lyon, France Purpose or Objective Vestibular schwannomas (VS) are rare and symptoms commonly include unilateral hearing deficiencies, tinnitus and loss of balance. The management of VS may involve surgery, radiotherapy or watchful waiting. In our institution, the required attitude is defined in a multi- disciplinary staff with neurosurgeons, radiologists, head and neck surgeons and radiation therapists. For patients addressed to radiation therapy, we chose to use hypofractionated stereotatic radiotherapy (HFSRT) in 3 or 5 fractions to benefit the radiobiological advantages of fractionation. This study assesses the outcome of HFSRT for VS at a single institution. Material and Methods We analyzed a retrospective case series. Patients were identified from patient records and a retrospective review of case notes and imaging reports was undertaken. All treatment was performed on a Cyberknife device. Two dose protocols were provided: 21 Gy in 3 fractions classically for stage II and for some stage III schwannomas and for the largest stage III 25 Gy in 5 fractions. All treatments were completed on a seven-day period. We assessed tumor response and recorded toxicity. Results From November 2010 to December 2016, 64 patients were treated in our institution for their VS with an HFSRT protocol. Ten (15.6%) patients had a previous surgery and were treated on a progressing schwannoma with a mean 50 months between surgery and radiation therapy (range:

Conclusion ReRT can be considered in appropriately selected patients with DIPG at progression with good symptomatic benefit, modest toxicity, and acceptable survival. Clinical improvement on reRT by the 10-15 th fraction can guide reRT dose in patients already on reRT. EP-1236 Volumetric assessment of cerebral edema after fractionated SRT for multiple brain metastases H. Inokuchi 1 , Y. Ishihara 1 , K. Okano 1 , A. Kawamura 1 , K. Tsutsui 1 , M. Hiraoka 1 1 Japanese Red Cross Society Wakayama Medical Center, Department of Radiation Oncology, Wakayama, Japan Purpose or Objective Fractionated stereotactic radiotherapy (FSRT) is emerging new technology which enables simultaneous irradiation for multiple, large brain metastases using linear accelerator (LINAC). The aim of this study was to evaluate local control and peritumoral cerebral edema after LINAC based FSRT as a first line therapy for multiple brain metastases.