ESTRO 36 Abstract Book

S601 ESTRO 36 2017 _______________________________________________________________________________________________

associated with progression ( p= 0.003). When stratified into 3 groups according to the surgical resection status and ART, the patients treated with STR alone showed significantly lower PFS, while those treated with GTR and STR plus ART did not (3-year PFS, 30.8% vs 91% vs 83.6%; p =0.013). Conclusion Although the most important prognostic factor related to progression was the surgical resection status, ART in patients with STR improved PFS, which is similar to those with GTR. Routine use of ART after STR is recommended. EP-1106 Local control and overall survival after frameless radiosurgery A. Bilger 1 , F. Frenzel 1 , O. Oehlke 1 , R. Wiehle 1 , D. Milanovic 1 , V. Prokic 2 , C. Nieder 3 , A.L. Grosu 1 1 University Medical Center Freiburg, Department of Radiation Oncology, Freiburg, Germany 2 University of Applied Sciences Koblenz, Department of Radiation Oncology and Medical Technology, Koblenz, Germany 3 Institute of Clinical Medicine, Faculty of Health Sciences- University of Tromsø, Tromsø, Norway Purpose or Objective Stereotactic radiosurgery (SRS) has been increasingly advocated for 1-3 small brain metastases. Goal of this study was to evaluate the clinical results in patients with brain metastases treated with SRS using a thermoplastic mask non-invasive fixation system and image-guided treatment. Material and Methods In this single-institution study 48 patients with 77 brain metastases were treated between February 2012 and January 2014. The head fixation was realized using a BrainLAB thermoplastic mask. The prescribed dose was 20 Gy or 18 Gy as a single dose. The SRS were performed with a True Beam STX Novalis Radiosurgery LINAC (Varian Medical Systems). The verification of positioning was done using the BrainLAB ExacTrac ® X-ray 6D system and cone- beam CT. Results In 69 of 77 (89.6%) treated brain metastases the follow-up was documented on MR imaging performed every 3 months. In 7/69 (10.1%) brain metastases local failure was diagnosed with a mean follow-up time of 10.7 months (range 1-43 months). Estimated 1-year local control was 83.1%. Median progression free survival (PFS) was 3.7 months, largely due to distant brain relapse. Breast cancer was significantly associated with a worse progression free survival. A GTV of ≤ 2.0 cm³ was significantly associated with a better PFS than a GTV > 2.0 cm³. We observed 2 cases of radiation necrosis diagnosed by histology after surgical resection. No other cases of severe side effects (CTACE≥3) were observed. Conclusion In our experience local control after frameless (ringless) LINAC based SRS with mean follow-up of 10.7 months is 89.9%. Without the invasive head fixation radiotherapy is more comfortable for the patients . EP-1107 Treatment Strategies for local and distant recurrence after HFSRT of the Resection Cavity A. Bilger 1 , E. Bretzinger 1 , H. Lorenz 1 , O. Oehlke 1 , A.L. Grosu 1 , S.E. Combs 2 , H.M. Specht 2 1 University Medical Center Freiburg, Department of Radiation Oncology, Freiburg, Germany 2 Klinikum rechts der Isar- Technical University of Munich, Department of Radiation Oncology, München, Germany Purpose or Objective In patients undergoing surgical resection of brain metastases the risk of local recurrence remains high (50- 60%). Adjuvant Whole Brain Radiation Therapy (WBRT)

can reduce the risk of local relapse but fails to improve overall survival. At the Departments of Radiation Oncology, University Medical Center Freiburg and Department of Radiation Oncology, Technical University Munich, a retrospective multicenter study was performed to evaluate the role of hypofractionated stereotactic radiotherapy (HFSRT) in patients with brain metastases after surgical resection. After a median follow up of 12.6 months (range 0.3 – 80.2 months) the crude rate for local control was 80.5% (Manuscript in preparation). In this analysis we evaluated the treatment strategies after intracranial local (LF) and locoregional (LRF) failure. Material and Methods 183 patients were treated with HFSRT of the surgical cavity after resection of brain metastases. In addition to the assessment of local control, distant intracranial control, overall survival and progression-free survival (manuscript in preparation), in this analysis we focused on the evaluation of individual patient histories and treatment strategies after intracranial recurrence. Results Imaging follow-up (cMRI) for the evaluation of LF and LRF was available in 160/183 (87%) patients.100/183 (63%) patients showed intracranial progression after HFSRT. At the first time of recurrence 81/100 (81%) patients received salvage therapy. Median time to the first recurrence was 5 months (6LF, 73LRF, 21LF+LRF). 14/81 patients underwent another surgery, 78/81 patients received radiation therapy as a salvage treatment (53% WBRT). Patients with single or few metastases distant from the initial site or WBRT in the past were re-treated by HFSRT (14%) or stereotactic radiosurgery (SRS, 33%). In case of second failure 32/48 patients received further salvage therapy (10WBRT, 18SRS, 4HFSRT). Median time to second recurrence was 10 months (5LF, 38LRF, 5 LF+LRF). Twelve patients developed a third failure (2LF, 8LRF, 2LF+LRF) after a median time of 14 months and 6 of them had a reirradiation (1WBRT, 4SRS, 1HFSRT). After a median time of 23 months 5 patients had a fourth recurrence (3LRF, 2LF+LRF) and 3 had another salvage treatment (2WBRT, 1SRS). Seven (3.8%) patients experienced radionecrosis. No other severe side effects (CTCAE≥3) were observed. Conclusion In our first analysis we have shown that postoperative HFSRT to the resection cavity is a highly effective concept leading to long-term local control after surgery (crude rate for local control was 80.5%). In this analysis we focused on salvage therapy in case of intracranial progression. 100/183 patients developed intracranial failure and 81 received a first salvage therapy. Thirty-two of 48 patients with a second recurrence, 6/12 patients with a third recurrence and 3/5 patients with a fourth recurrence received salvage treatment without severe side effects. Local failures are rare and distant intracranial failures can be effectively salvaged by further radiotherapy. EP-1108 CyberKnife® stereotactic radiation therapy for re-irradiation of recurrent high grade gliomas. H. Grzbiela 1 , M. Stąpór-Fudzińska 2 , E. Nowicka 1 , M. Gawkowska 1 , R. Tarnawski 1 1 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, III Radiotherapy and Chemotherapy Clinic, Gliwice, Poland 2 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Radiotherapy Planning Department, Gliwice, Poland Purpose or Objective Patients suffering from brain tumors, especially high grade gliomas (HGG), often have to face a recurrence of the tumor, after the primary treatment. Stereotactic radiotherapy with CyberKnife ® seem to offer a valuable treatment option.