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ESTRO 37

Hernández 1 , L. Brualla González 1 , F. Perruca Salvador 2 , A. Salvador Montaño 1 , J. Roselló Ferrando 1 , J. López Torrecilla 2 1 Eresa-Hospital General Universitario Valencia, Radiation Physics Department, Valencia, Spain 2 Eresa-Hospital General Universitario Valencia, Radiation Onclogy Department, Valencia, Spain Purpose or Objective In the radiotherapy process there are some uncertainties as accuracy of fusion images, contouring, precision of positioning and image guidance during the treatment, intrafraction motion and some others that will affect the margins of the GTV to the PTV. The purpose of this work is to evaluate the intrafraction motion for SRT/SRS treatments with a thermoplastic immobilization mask. Material and Methods In our centre we irradiate SRT/SRS patients in a TrueBeam 2.0 linac with a thermoplastic immobilization mask form BrainLab. Patient positioning is done by means of a pair of orthogonal kV-kV images in each treatment fraction, and in some cases with a CBCT. The images are fused with the CT and the displacements are obtained. In order to obtain the intrafraction motion a second pair of kV-kV images is done at the end of the treatment. Results We have evaluated the intrafraction motion in 255 treatment fractions. The average time of treatment was 7.6 min. The average intrafraction motion was 0.5 mm (max. 1.9 mm) in the vertical direction, 0.6 mm (max. 2.0 mm) in the longitudinal direction and 0.5 mm (max. 1.9 mm) in the lateral direction. We have used the Van- Herk margin recipe to obtain the margin to include the intrafraction motion. The margin obtained for the vertical, longitudinal and lateral direction was 1.6 mm, 1.7 mm and 1.5 mm, respectively. Currently we define PTV as GTV with an isotropic-margin of 2 mm. Conclusion Results show that, although the average intrafraction movement is less than 0.6 mm, there are fractions in which this movement is up to 2 mm and we must take it into account to obtain the optimal expansion from GTV to PTV for SRT/SRS treatments. EP-1208 Primary radiotherapy treatment for patients with multifocal glioma - a case series of 12 patients D.F. Fleischmann 1 , R. Schön 1 , C. Belka 1 , M. Niyazi 1 1 LMU Munich, Department of Radiation Oncology, Munich, Germany Purpose or Objective Multifocal occurrence of glioma at primary diagnosis is a rare condition, but known to be of particular poor prognosis. To gain further insights into this severe form of disease we studied 12 unselected cases treated between April 2011 and January 2017 in our institution. Material and Methods Patients with multifocal glioma occurrence treated with radiotherapy were included into the analysis. Histopathological examination was evaluated for IDH mutation status and MGMT methylation status. Treatment volumes were evaluated on OTP-Masterplan ® including GTV, PTV, V30Gy, V45Gy and D2%. Kaplan-Meier estimators were calculated for overall and progression- free survival from the start of radiation therapy until death or diagnosis of progression of disease/death. Results 12 glioma patients with multifocal occurrence of disease (1 anaplastic astrocytoma, 11 glioblastoma patients) were included. Histopathological examination revealed IDH wild-type tumours in all patients and MGMT methylated tumours in 4 patients. Subtotal resection was performed in 2 patients and stereotactic biopsy in 10 patients before the start of radiation therapy. At the start of radiation therapy patients were 57 years old in

Results Between October 2014 and December 2016, 41 patients with 53 spinal metastases were treated. The median follow-up was 8 months (range, 1 - 28). The median prescribed dose to PTV and PTV boost were 30 Gy (range, 24 - 30) and 35 Gy (range, 27 - 35), respectively; treatments were delivered in 3 - 5 fractions. The 1-year freedom from treatment failure rate was 97%. The 1-year and 2-year OS rates were 49% and 19%, respectively. All cancer related deaths were due to primary disease progression. There were 2 cases (6.3%) of symptomatic vertebral fracture; no case of radiation-induced myelopathy was observed. Conclusion Spine SABR with simultaneous integrated boost is feasible and provides satisfactory local control. Regarding the good results and the low morbidity rate, more work should be done to integrate spine SABR in the management of spine metastases even in palliative intent. EP-1206 Outcomes of SIB-IMRT with concurrent temozolomide in patients with glioblastoma multiforme J.A. Lee 1 , D.S. Yang 1 , C.Y. Kim 2 , W.S. Yoon 3 , Y.J. Park 2 , N.K. Lee 2 , C.H. Im 3 1 Korea University Guro Hospital, Department of Radiation Oncology, Seoul, Korea Republic of 2 Korea University Anam Hospital, Department of Radiation Oncology, Seoul, Korea Republic of 3 Korea University Ansan Hospital, Department of Radiation Oncology, Seoul, Korea Republic of Purpose or Objective We investigated the outcomes of simultaneous integrated boost intensity modulated radiotherapy (SIB-IMRT) with concurrent temozolomide in patients with pathologically confirmed glioblastoma multiforme (GBM). Material and Methods Between January 2010 and December 2016, 39 patients with GBM were treated with SIB-IMRT with concurrent temozolomide. Thirty of these patients were analyzed except 9 patients who lost follow up or missed subsequent brain magnetic resonance images (MRI). A dose of 2.0 Gy was delivered to the clinical target volume (CTV) with a SIB 0.2 Gy to the gross tumor volume (GTV) with a total dose of 66 Gy to the GTV and 60 Gy to the CTV in 30 fractions during 6 weeks. Results Median age was 71.5 years (range 29-84 years). Twenty- four patients (80%) were Zubrod performance score 0 or 1, and 6 patients (20%) were score >2. Median survival was 13 months with a median follow up of 12 months (range, 4-46 months). Seven patients (23.3%) were treated with gross total resection (GTR) prior SIB-IMRT while 23 (76.7%) treated with subtotal resection (STR) or stereotactic biopsy only. Overall local control rate was 50% with median progression free survival of 10 months. Extent of surgery (GTR VS less than GTR) was significant factor for in-field control. (p<.05, 85% VS 39%) Of 15 patients who had recurrences, 4 patients had in-field failure, 3 patients had in and out-field failure, 10 patients had in or out-field failure with suspected seeding, and one patient had spinal metastasis. Toxicities were acceptable. Conclusion In this study, SIB-IMRT with concurrent temozolomide in patients with GBM was feasible with comparable survival outcomes to previous studies. To further confirm the evident clinical advantage of SIB-IMRT, additional investigation is needed. EP-1207 Evaluation of the intrafraction motion in SRT- SRS treatments D. Granero Cabañero 1 , P. Almendros Blanco 2 , A. Hernández Machancoses 2 , A. Vicedo González 1 , T. García