ESTRO 36 Abstract Book

S607 ESTRO 36 _______________________________________________________________________________________________

after completion of treatment (median time to recurrence was 9 months). In 8 patients partial tumor resection was performed (pathology was confirmed as glioblastoma G4 in this group). All patients were planned for re-irradiation. CyberKnife ® stereotactic radiation therapy was used. Total dose and dose per fraction delivered to tumor depeneded mainly on tumor volume and time interval after the first course of radiation therapy. The irradiated tumor volume ranged from 9.4 to 75.7 cm 3 . 4 patients received 18 Gy in 3 fractions, 14 patients – 16 Gy in 2 fractions, 11 patients – 12 Gy in 2 fractions, and 4 patients – 8 Gy in a single fraction. Results All patients completed the stereotactic radiation therapy. 82% of patients reported mild or moderate headache (CTCAE grade 1 or 2). No grade 3 or 4 acute toxicity was observed. Follow-up time after re-irradiation was 3 – 48 months (median 12 months). Progression-free survival was 3 – 39 months (median 6 months). The early results were assessed with MRI scans performed 3 months after the stereotactic radiation therapy. Stable disease was observed in 5 patients (15.2%). Partial tumor regression was observed in 6 patients (18.2%). Conclusion In our experience, CyberKnife ® stereotactic radiation therapy can be considered as a valuable treatment option, which can slow down the inevitable progression of high grade gliomas in about 30% of patients. It also seems to be a safe method of re-irradiation, provided that the total dose and dose per fraction are chosen carefully and individually. EP-1109 measurement of hippocampus atrophy after whole brain irradiation using voxel based morphometry T. Ito 1 , Ｍ . Nishihara 2 , S. Takaki 2 , Y. Tani 2 1 Japanease Redcross society nagaoka hospital, radiaton therapy, Nagaoka, Japan 2 Japanease Redcross society nagaoka hospital, radiology, Nagaoka, Japan Purpose or Objective To estimate the adverse effect of whole brain radiation therapy (WBRT), especially cognitive disorder, we measured retrospectively about mesial temporal lobe size after WBRT using voxle based morphometry in cancer patients. Material and Methods From 2013 to 2015 ,11 cancer patients with multiple brain metastasis ( 7 men and 4 women , average age was 59 years) were examined by gadrinium enhanced MRI before and after WBRT. The sequence was followed; T1-weighted 3D-variable flip angle sagital image in 1mm slice thickness ,using 1.5T MRI scanner, and it is routine sequence in our hospital for cancer patient's examination. And this image set was analysed ｂｙ voxel based morphometry from the view point of the ratio of the mesial temporal lobe to the whole brain . Voxel based morphometry software was VSRAD advanced 2 ,and this program was generally used for Alzheimer's disease evaluation. Images were obtained before WBRT, and after several month in variable periods.(longes ｔ case was 14 months) Results 33 MRI image was analysed and calculate by VSRAD advanced2 . The examinations with severe brain edema or huge metastasis were excluded . 2 patients were alive and 9 patients were dead by original disease ( include caused by brain metastasis) . In only one patient, mental disturbance was occurred clinically,but other patients were not reported metal disorder by clinician. No patient

was examined mini-mental state examination. Temporary increase tendency of hippocampus atrophy compared to whole brain were observed in the period of about 4 months after WBRT. But reliability was low statistically.

Conclusion A minimal change of hippocampus size was observed , but it might be a measurement error . Further investigation is needed ,especially more number of cases. Furthermore, from the perspective of with or without of chemotherapy, or comparison to after stereotactic radiosurgery aleno are required. EP-1110 Evaluation of [18F]FET-PET and MRI assessed recurrence pattern in patients with high-grade glioma J. Hesse 1,2 , K. Kessel 1 , H. Specht 1 , M. Schwaiger 3 , T. Pyka 3 , C. Zimmer 4 , S. Combs 1,2 1 Technical University Munich TUM, Department of Radiation Oncology, München, Germany 2 Institute of Innovative Radiotherapy iRT, Department of Radiation Sciences DRS, Neuherberg, Germany 3 Technical University Munich TUM, Nuclear Medicine, München, Germany 4 Technical University Munich TUM, Department of Neuroradiology, München, Germany Purpose or Objective Despite multidisciplinary therapy concepts the prognosis of high-grade glioma (HGG) remains poor and recurrence is frequent. In this analysis, we evaluated the recurrence pattern and gross tumor volume (GTV) comparing two different imaging techniques: MRI and [ 18 F]FET-PET. Our aim was to identify high-risk areas for recurrence in order to optimize concepts of radiotherapy-planning. Material and Methods We analyzed 14 patients with HGG (WHO °III: n=6, WHO °IV: n=8) treated in our department. All patients were incompletely resected received adjuvant radiotherapy. GTV and tumor volume at recurrence (RecTV) definition was based on MRI (GTV MRI, RecTV MRI ) and FET-PET (GTV PET, RecTV PET ). In order to evaluate the recurrence pattern, the percentage of RecTV PET and RecTV MRI residing within the planning target volume (PTV) was determined. We classified RecTV as 'in-field” if more than 90% of RecTV was detected inside PTV, as 'field-border” if 30-90% and as 'out-field” if less than 30% was located within PTV. We compared the volumes and calculated various intersection (IV) and conjunction volumes (CV) as well as the conformity index (CI=IV/CV). CI takes not only volumetric size into account, but also the extend of overlap. For image fusion and target definition iPlan RT® (BrainLab, Munich, Germany) and Eclipse® (Varian, Palo Alto, US) were used. Results Median PTV was 192.9 ml (range 10.1-490.8 ml). RecTV PET and RecTV MRI showed no major differences concerning recurrence localization: In-field recurrence was detected in 64% (9/14), field-border in 29% (4/14) and out-field 7% (1/14). We were not able to evaluate the RecTV MRI of one