ESTRO 2023 - Abstract Book

S886

Digital Posters

ESTRO 2023

1 Kantonsspital Aarau, Radiology Oncology Centre KSA-KSB, Aarau , Switzerland; 2 Kantonsspital Aarau, Neurology, Aarau , Switzerland; 3 Kantonsspital Aarau, Radiation Oncology Centre KSA-KSB, Aarau, Switzerland; 4 Kantonsspital Aarau , Radiation Oncology Centre KSA-KSB, Aarau , Switzerland; 5 Kantonsspital Aarau, Radiation Oncology Center KSA-KSB , Aarau, Switzerland Purpose or Objective Stereotactic re-irradiation (re-SRT) is an option for patients with recurrent glioblastoma (GBM). Unlike postoperative RT, where up to 2.5 cm margins may be added for potential microscopic spread, re-SRT typically uses 0 mm margins due risk of radionecrosis. The aims of this study were to investigate the radiological patterns of relapse after first and second irradiation. We also evaluated clinical outcomes and compared these with the literature. Materials and Methods Selected patients with recurrent GBM received re-SRT with 10 x 3.5 Gy, 99% of the PTV received 100% dose and PTV=GTV. Volumes were contoured using a 1.5T MRI (Elements, Brainlab, Germany) and delivered with a Novalis STx (Varian, USA/ Brainlab). Radiological outcomes were assessed on successive Gd_T1 3D and FLAIR MRI sequences. Clinical endpoints were local control, overall survival and toxicity. Results 14 patients with recurrent GBM received re-SRT between 12/2015 and 08/2022. Eight patients were male, six were female and the median age was 61 yrs (41-77). All patients had previously received either resection followed by 30 x 2 Gy with concomitant temozolomide (TMZ) or 15 x 2.67 Gy with TMZ according to MGMT methylation status. 9/14 patients underwent re-resection and 7/14 had had at least one second-line systemic therapy prior to re-SRT. Of 10 evaluable patients, 8 recurrences were in-field having received a mean dose of 101.2% (97.1-103.3%) of the initial prescription, 1 was marginal (Dmean 90.1%, Dmin 56.9%, Dmax 104.3%) and 1 was distant (Dmean 33.9%, Dmin 24.7%, Dmax 59.7%). 5/10 had a second operation prior to re-SRT and anatomical shifts could not be excluded. The out of field recurrence did not show a 'leading edge' on FLAIR MRI prior to the new contrast-enhancing lesion 5 months after initial RT, nor did the marginal recurrence develop within the initial FLAIR signal. The median time to re-SRT following completion of adjuvant RT was 29 mths (7 224) and the median PTV at re-SRT was 6.6 cm3. Two patients received TMZ and two received bevacizumab concomitantly. Eleven patients had a follow-up MRI following re-SRT. Three patients had no evidence of tumour progression (mean follow up 6 months, range 2.2-9.6). Five progessions were in-field, 1 was marginal and two were distant. Median progression-free survival following re-SRT was 5.8 mths (2.2-41.8). Five patients subsequently received bevacizumab (one combined with lomustine) and one was re-challenged with TMZ. The median overall survival was 8.3 months (1.5-92.5) and the six month overall survival rate was 79%, comparable to 73% reported in a meta-analysis of 50 papers. There were no documented related toxicities. Conclusion Median PFS, OS and toxicity in our series compared favourably with those reported in the literature. The pattern of relapse after re-SRT for GBM was similar to that described after first irradiation. Re-SRT with 10 x 3.5 Gy is a clinically meaningful option in selected patients with circumscribed recurrent GBM. M.G. Carnevale 1 , A. Romei 1 , I. Bonaparte 1 , I. Morelli 1 , M. Banini 1 , I. Desideri 1 , V. Salvestrini 2 , L. Visani 3 , B. Detti 1 , D. Greto 1 , L. Livi 1 1 University of Florence, Radiation Oncology Unit, Azienda Ospedaliera Universitaria Careggi, Florence, Italy; 2 Istituto Fiorentino di Cura ed Assistenza (IFCA), CyberKnife Center, Florence, Italy; 3 stituto Fiorentino di Cura ed Assistenza (IFCA), CyberKnife Center, Florence, Italy Purpose or Objective Brain metastases (BMs) account for more than one-half of all intracranial tumors. Over the past years, stereotactic radiosurgery (SRS) has become the mainstay of BMs treatment, providing high rates of local tumor control. Nevertheless, SRS alone is associated with a 30-50% risk of distant brain failure (DBF), consequently requiring careful follow-up and possible rescue treatments. Silibinin or silybin, a natural polyphenolic flavonoid, has shown promising antitumor activity, leading to improvement of BMs in patients (pts) with progressive non-small cell lung cancer. Therefore, our exploratory study aims to evaluate whether the use of a silibinin-based nutraceutical (SILLBRAIN®, HEALTH4U S.r.l.) can significantly reduce DBF rate at 6 months in pts with first-diagnosed BMs treated with SRS with or without surgery. Materials and Methods SUSTAIN is an interventional, prospective, single arm, phase II study. A total of 80 pts treated in our center are planned to be enrolled. Pts receive 2 capsules (cps) of SILLBRAIN® per day for the first month after SRS and 1 cp per day thereafter. Primary endpoints are 6-month distant brain failure (DBF) rate and safety; secondary endpoint is 6-month overall survival (OS) rate. Contrast-enhanced magnetic resonance (MRI) of the brain is performed at baseline and every 12 weeks after SRS treatment; radiological response is assessed according to RANO criteria for brain metastases (RANO-BM) Results Thirty pts has been enrolled at the time of this primary analysis (Tab1). NSCLC and breast cancer were the prevalent histologies (14 and 10 cases respectively). Twelve pts were chemotherapy naive at the time of BMs diagnosis; 10 pts has received 1 systemic therapy line and 8 pts has received 2 lines or more. Overall, the number of treated lesions was 73, with a median of 1 lesion (range 1-9). All pts underwent SRS, with a median prescription dose (PD) and a median prescription isodose line (IDL) of 24 Gy and 80% respectively. After a 14-month enrollment period, with a median follow-up of 9 months, 6 pts reported distant intracranial failure according to RANO-BM criteria, with a 6-month DBF rate of 20%. Only 1 treated lesion met the criteria for progression, accounting for a 6-month local control (LC) rate of 98%. Six pts died, with a 6-month PO-1109 Safety and efficacy of silibinin in patients with brain metastases after SRS: SUSTAIN trial