ESTRO 38 Abstract book

S383 ESTRO 38

Long-term follow-up confirmed the excellent tumor control associated to SRS of VS. Although the median administered dose was rather high, iatrogenic toxicity was acceptable and similar to that reported in literature. PO-0748 Prognostic factors of distant brain failure free survival after stereotactic RT for brain metastasis Y. Pin 1 , M. Loo 1 , A. Paix 1 , P. Meyer 2 , D. Antoni 1 , F. Proust 3 , G. Noël 1 1 Centre de Lutte Contre le Cancer, Radiation Oncology, Strasbourg, France ; 2 Centre de Lutte Contre le Cancer, Medical Physic, Strasbourg, France ; 3 Strasbourg University Hospital, Neurosurgery, Strasbourg, France Purpose or Objective Brain metastasis (BM) is a frequent evolution in patients with solid cancer. Treatements with whole brain radiotherapy (WBRT) demonstrated a benefit in overall survival (OS) but their indications are becoming controversial due to the induced cognitive impairment. The reduction of the use of WBRT is for the benefit of the stereotactic radiation therapy (SRT). Nevertheless, SRT rarely improved significantly the OS provided by the WBRT and suffers of higher distant metastasis rates. In this study, we tried to find prognosis factors of distant brain failure free survival (DFS) that might permit to refine the indications of the use of WBRT in patients treated for BM with SRT. Material and Methods Clinical, biological and imaging factors were retrospectively recorded from patients referred for upfront stereotactic radiotherapy of one to three BMs. Those factors included a new edema descriptor, the Edema Theoretical Thickness (ETT) defined by the difference of radius between a first perfect sphere which volume corresponds to the sum of BMs volumes and a second perfect sphere which volume corresponds to the sum of brain edemas volumes. DFS was studied in function of these factors with the Cox proportional hazards regression model. Relevant factors were selected by an univariate analysis. The most relevant non-colinear factors were selected using the Farrar-Glauber test. Then, the multivariate analysis was performed to find the significant factors predicting the DFS. Results Between January 2012 to December 2017, 182 patients were included. Factors found significant by the multivariate analysis on the DFS were the ETT (HR = 0.92, p = .022 ) with a better DFS in patients with an ETT > 7.5 mm ( p logrank = .011 ), the melanoma histologic type ( 2.67, p = .034 ) and the BM local relapse after SRT (2.65, p=.018 ). Conclusion In this study, we found that the survival free of distant brain failure is independently correlated to the melanoma histologic type, the local failure after SRT and the ETT. ETT appeared to reflect a potential abscopal-like effect in case of SRT for BM and should be included in further studies. The combination of BMs SRT with immunotherapy could be a further way of research. PO-0749 New apects regarding the treatment of glioblastoma C. Matuschek 1 , B. Tamaskovics 1 , E. Boelke 1 , W. Budach 1 , F. Djiepmo 1 , J. Haussmann 1 , A. Kumar 2 , H. Pokhylevych 2 , D. Schomer 2 , A. Hayman 2 1 University Hospital Düsseldorf, Radiation Oncology, Düsseldorf, Germany ; 2 MD Anderson, Neuroradiology, Houston, USA Purpose or Objective Since 60 years no accurate classification system exists for glioblastoma. Furthermore, the treatment results are still very poor with a low survival rate. To understand the

recurrence within the irradiated field (50-60 Gy); 7 (21.2%) experienced out-field failure (2 cases of marginal failure, 2 cases of corpus callosum metastasis, 1case of pineal gland metastasis, 1 case of contralateral brain metastasis, 1case of distant intraparenchymal This study was the first to explore the clinical value of fMRI in the delineation of radiotherapy target volume for HGG. It suggested that combination of fMRI and CE-MRI may improve the survival outcome compared to the traditional guidelines, and may reduce the risk of distant metastasis for HGG patients. metastasis). Conclusion PO-0747 Results at long-term after linac-based radiosurgery of vestibular schwannomas P. Anselmo 1 , M. Casale 1 , F. Trippa 1 , F. Arcidiacono 1 , S. Fabiani 1 , A. Di Marzo 1 , L. Draghini 1 , S. Terenzi 1 , E. Maranzano 1 1 Ospedale Santa Maria, Radiotherapy Oncology Centre, Terni, Italy Purpose or Objective Vestibular Schwannomas (VS) are benign tumors generally arising from vestibular component of the vestibulocochlear nerve. Hearing loss is the most common initial presenting symptom. This report regards patients with sporadic VS undergone linac-based radiosurgery (SRS) with a follow-up > 10 years. Material and Methods Between August 2002 and January 2008, 53 patients with 53 sporadic VS were treated. Patients not able to discriminate words or not hearing at all, were scored as ‘non-serviceable hearing’. Trigeminal and facial nerve functions were assessed asking the patient about facial pain/paraesthesia. Median dose of SRS was 16.5Gy (range, 13-20Gy). Results Male/female ratio was 27/26. The median age was 59 years (range, 23-83). The median tumor volume was 1,7 cc (range, 0.09-7.4). Surgery has been performed before SRS in 14 (26%) patients (total or subtotal resection 5- 9% and 9-17% patients, respectively). In these cases SRS was performed as salvage therapy for recurrent or progressive tumors. Other 39 (74%) patients underwent SRS alone. Fifty (94%) of patients had hearing loss as an initial symptom and 27 (51%) a “non-serviceable” hearing function. Ataxia, tinnitus, trigeminal neuralgia and facial pain/paraesthesia were presenting symptoms in 10 (19%), 8 (15%), 4 (7.5%) and 10 (19%) of the patients, respectively. Considering that 5 patients were lost to follow up, 48 (92%) patients were evaluable. At a median follow-up of 12 years (range, 2–16), 10 patients (21%) had an objective improvement of their initial symptoms with a MRI response classifiable as stable, partial or complete remission in 6, 3 and 1 patient, respectively. Twenty-one (44%) patients had stable symptoms, with a MRI showing stable disease, transient enlargement due to central tumor necrosis, or partial remission in 10,3,8 patients, respectively. Seventeen (35%) patients worsened their pre-treatment symptoms. This deterioration was transient in 12 patients and persistent in 5. In “serviceable-hearing” patients, 10-year hearing preservation rate was 92%. Four of 38 (11%) patients without pre-SRS facial toxicity, developed incomplete facial nerve palsy, that regressed in a median time of 6 months. Eleven of 44 (25%) patients without pre-SRS trigeminal neuralgia developed trigeminal toxicity which was transient or stable/mild during follow- up in 10 (23%) patients (median tumor size 18mm, median dose of 17Gy). In only 1 case (2%) trigeminal toxicity was severe and appeared 12 months after SRS (tumor size was 18.8mm and prescribed dose 16,5Gy). Crude radiologic tumor control rate was 100%. Conclusion