ESTRO 2022 - Abstract Book

S966

Abstract book

ESTRO 2022

cavity. Pts received 2 capsules (cps) of SILLBRAIN® per day for the first month after SRS and 1 cp per day thereafter. The 6-month DBF rate is assessed according to RANO criteria for brain metastases (RANO-BM). Contrast-enhanced magnetic resonance (MRI) of the brain is performed at baseline and every 12 weeks after SRS as per clinical practice. EORTC QLQ- C30 and BN20 questionnaires are administered at baseline and every 12 weeks after SRS to evaluate health-related quality of life (HRQoL). Results At the time of this first analysis 18 pts have been enrolled. The prevalent primary tumors were NSCLC and breast cancer, with 9 and 4 pts respectively. Ten pts had metachronous BMs onset, and 8 pts synchronous. Nine pts received at least 1 line of systemic therapy and 17 pts reported a controlled extracranial disease at BMs diagnosis. The overall number of BMs was 55. All BMs were treated with SRS, with a median prescription dose and median prescription isodose of 24Gy and 80%, respectively. According to RANO-BM criteria, 1 pt reported distant intracranial failure with 3 months of DBF. The median OS was 8 months. Only 1 pt discontinued SILLBRAIN® assumption due to the onset of grade 1 nausea (CTCAE v5.0). No other adverse events were reported. Conclusion The addition of silibinin-based nutraceuticals after SRS administration might improve intracranial disease control in BMs pts, with a good safety profile. Final results from SUSTAIN trial are awaited to confirm these encouraging findings. C. Silva 1 , M. Amorim 1 , M.A. Costa 2 , G. Fonseca 2 , C. Fardilha 2 , J. Gagean 2 , S. Simões 1 , F. Ponte 2 , G. Campos 2 , C. Seixas 2 , F. Rodrigues 2 , P. Costa 1,2 1 Hospital de Braga, Radiation Oncology, Braga, Portugal; 2 CUF Porto Instituto - Júlia Teixeira S.A., Radiation Oncology, Porto, Portugal Purpose or Objective Vestibular schwannoma (VS) is a type of non-cancerous brain tumor. This type of tumor grows on the vestibulocochlear nerve (cranial nerve VIII), which is responsible for control balance and hearing. Stereotactic radiosurgery (SRS) has evolved as a first-line alternative treatment for small VS. Our purpose was to study the outcomes of SRS using Cyberknife (CK) in terms of tumor control, hearing and side effects in the treatment of VS. Materials and Methods We retrospectively analysed the data of 28 patients with the diagnosis of VS (11 male and 17 female) who underwent treatment with Cyberknife®, between 2016 and 2021 at our institution, with a dose of 12Gy/18Gy (single fraction), 18Gy/21/24Gy (3 fractions) and 25 Gy (5 fractions). Audiograms were performed before and after SRS to evaluate auditory function, and the radiological tumor control was evaluated using magnetic resonance imaging. Age, pre and postoperative tumor size, tumor coverage, normalized conformity index and adverse events were collected and analysed for all patients. Results The mean age was 56 years (range 38–79). Mean CTV volume was 2.56 cm 3 (0.14-15.04 cm 3 ) and mean PTV volume was 3.76 cm 3 (0.47-20.06 cm 3 ). The average conformity index was 1.21 (1.08-1.58). The PTV coverage of at least 95% was obtained by prescribing the therapeutic dose to isodose lines ranging from 69.7 to 89.3%. The mean follow-up time was 28 months (1–65 months). Radiological tumor control revealed that 20 patients (71%) showed a decrease of initial tumor size, 7 patients (25%) showed stable tumor and 1 (4%) presented an initial decrease in size but with a tumor growth 2.5 years after CK-SRS. Three (10,7%) of 28 patients presented lost hearing prior to treatment. The 25 cases (88%) with preserved hearing remained stable at the last follow-up. Mild adverse events were temporarily in four patients (14%): one with CTCAE (CTCAE v5.0) grade 1 facial nerve disorder, two with grade 1 headache and one with CTCAE grade 2 facial muscle weakness. Seven (25%) patients described permanent mild symptoms: CTCAE grade 2 without limiting daily life (vision decreased n=2) and grade 1 (facial weakness n=3, vertigo n=2). The patients with hearing deterioration had larger tumour volumes and poorer hearing prior to radiosurgery. Conclusion CyberKnife Stereotactic Radiosurgery is an excellent alternative treatment modality for patients with vestibular schwannoma, as is a well-tolerated and effective regimen. Treatment goals are long-term tumor control, hearing preservation and concurrently low side-effects. Our results revealed an excellent tumor control rate and acceptable preservation of hearing, with mild side effects, consistent with those reported in the literature. PO-1138 Stereotactic radiosurgery in the management of vestibular schwannoma:a single-institution experience

PO-1139 Hypofractionated radiotherapy for glioblastoma: therapeutic outcomes, toxicities and quality of life

F. Dhouib 1 , S. Zouari 1 , N. Fourati 1 , M. Kallel 1 , W. Siala 1 , W. Mnejja 1 , J. Daoud 1

1 Habib Bourguiba University Hospital, Oncology-radiotherapy, Sfax, Tunisia

Purpose or Objective Glioblastoma (GB) is the most common primary malignant brain tumor in adults. Despite improvements in survival with aggressive chemoradiation, outcomes remain poor. Though the literature supports the use of standard radiotherapy (SRT) (60 Gy in 30 fractions), several randomized studies have supported the use of hypofractionated regimen especially for