EP-1106: Local control and overall survival after frameless radiosurgery

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Purpose or Objective Hippocampal-dependent neurocognitive functions, including learning, memory and spatial informations processing, could be affected by brain radiotherapy. Aim of the present study is to evaluate the dose to omolateral and contralateral hippocampus (O-H, C-H, respectively) during Stereotactic Radiotherapy (SRT) or Radiosurgery (SRS) for brain metastases (BM). Material and Methods Patients eligible for SRS/SRT treatment had a number of BM <5, with a size ≤30mm, Karnosky Performance Status (KPS) ≥ 80 and a life expectancy over 3 months. Gross Tumour Volume (GTV) was delineated by the fusion between Magnetic Resonance Imaging and Computed Tomography. A Planning Target Volume (PTV) was obtained from GTV by adding a 2mm isotropic margin. The total dose ranged between 18-27 Gy in 1-3 fractions. For each BM, a Volumetric modulated arc therapy plan was generated with one or two arcs and hippocampus sparing was not considered during optimizations phase. For the dosimetric evaluation of O-H and C-H, the Dmedian, Dmean, D0.1cc and the V1Gy, V2Gy, V5Gy and V10Gy were analyzed. Results From April 2014 to December 2015, 81 BM in 41 patients were treated with SRS/SRT and selected for the present analysis. The average value of PTV dimension and hippocampus volumes were (5.8 + 9.5) cc and (1.1 + 0.3) cc, respectively. For the O-H, the average values of Dmedian, Dmean and D0.1cc were (1.5 + 3.65) Gy, (1.54 + 3.6) Gy, (2.2 + 4.7) Gy, respectively, while the V1Gy, V2Gy, V5Gy and V10Gy values were (25 + 40) %, (18.9 + 35) %, (8.9 + 25.3) % and (2.1 + 11.8) %, respectively. For the C-H, the average Dmedian, Dmean and D0.1cc were (0.7 + 1.5) Gy, (0.7 + 1.4) Gy, (0.9 + 1.8) Gy, respectively, while the average values of V1Gy, V2Gy, V5Gy and V10Gy were (18 + 35) %, (10.2 + 27.7) %, (2.8 + 15.4) % and (1.4 + 11.6) %, respectively. The differences between O-H and C-H, in terms of received dose, was statistically significant (p=0.03). Moreover, the PTV dimension (>5cc or >6cc) did not influenced the dose of hippocampus (p= 0.06; 0.2, respectively). Conclusion During SRT/SRS treatments for BM, hippocampus received a very low dose and its clinical significance seems to be negligible, even if it is still under investigation. However, considering the increasing use of SRS/SRT for multiple BM, including also patients with up to 10 BM, the dose to hippocampus need to be seriously evaluated in the treatment planning. EP-1104 SABR for brain metastases with VMAT and FFF: feasibility and early clinical results N. Giaj Levra1, A. Fiorentino1, G. Sicignano1, U. Tebano1, S. Fersino1, R. Mazzola1, F. Ricchetti1, D. Aiello1, S. Naccarato1, R. Ruggieri1, F. Alongi1 1 Sacro Cuore Don Calabria Cancer Care Center Hospital, Radiation Oncology, Negrar-Verona, Italy Purpose or Objective For selected patients with brain metastases (BMs), the role of stereotactic radiosurgery (SRS) or stereotactic fractionated radiotherapy (SFRT) is well recognized. The recent introduction of Flattening-Filter-Free (FFF) delivery during linac-based SRS or SFRT allows shorter beam-on-time, improving patients’ comfort and facility workflow. Aim of the present study was to analyze SRS/SFRT linac-based FFF-delivery for BMs in terms of dosimetric and early clinical results. Material and Methods Patients with life expectancy > 3 months, number of BMs < 5, diameter < 3cm and controlled or synchronous primary

tumor, received SRS/SRT. The prescribed total dose and fractionation, based on BMs size and proximity to organs at risk, ranged from 15Gy in 1 fraction to 30Gy in 5 fractions. A FFF-Volumetric Modulated Arc Therapy (VMAT) plan was generated with one or two coplanar partial arcs. Toxicity was assessed according to CTCAE v4.0. Results From April 2014 to February 2016, 45 patients (89 BMs) were treated with SRS/SFRT linac-based FFF-delivery. The mean beam-on-time was 140 seconds for each lesion (range 90-290 seconds) and the average brain Dmean was 1Gy (range 0.1 - 4.8 Gy). With a median follow-up time of 12 months (range 1-27 months), the median overall survival was 14 months and the 6-month overall survival was 77% and. At the time of analysis local control was reported in 83 BMs (93.2%) and 6-month actuarial rates was estimated in 76.4%. Finally, the median intracranial disease control was 11 months. Acute and late toxicities were acceptable without severe events (no adverse events ≥ G2 were recorded). Conclusion These preliminary results confirmed the feasibility and safety of linac-based SRS/SFRT with FFF delivery for BMs patients. A longer follow-up is necessary to assess the definitive efficacy and tolerability of SRS/SFRT with FFF in BM patients. EP-1105 Treatment Outcomes and Prognostic Factors of Atypical Meningioma: A Single-Institution Experience H.J. Kang1, B.O. Choi1 1 The Catholic University of Korea- Seoul St.Mary's Hospital, Radiation onconlogy, SEOUL, Korea Republic of Purpose or Objective We aimed to evaluate the treatment outcomes and prognostic factors in patients with atypical meningioma. Material and Methods From 2001 to 2016, 131 patients were retrospectively reviewed in this study. All patients were treated with surgical resection and histologically confirmed as atypical meningioma. The histology grading was defined by the 2000/2007 WHO classification. Ninety-five patients (75.5%) underwent gross-total resection (GTR) and 36 patients (27.5%) underwent subtotal resection (STR). Of the 36 patients treated with STR, 20 (15.7%) received adjuvant radiation therapy (ART). Results The median follow-up time was 36 months (range, 6-152 months). The 3- and 5-year progression-free survival (PFS) rates were 81.8% and 74.6%, respectively, and the 3- and 5-year overall survival rates were 93% and 86.5%, respectively. Only the surgical resection status was significantly associated with disease progression (p=0.002). In the STR subgroup, ART was also significantly 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. Bilger1, F. Frenzel1, O. Oehlke1, R. Wiehle1, D. Milanovic1, V. Prokic2, C. Nieder3, A.L. Grosu1 1 University Medical Center Freiburg, Department of

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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 conebeam 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. Bilger1, E. Bretzinger1, H. Lorenz1, O. Oehlke1, A.L. Grosu1, S.E. Combs2, H.M. Specht2 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 (5060%). 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. Grzbiela1, M. Stąpór-Fudzińska2, E. Nowicka1, M. Gawkowska1, R. Tarnawski1 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. Material and Methods 33 patients diagnosed with HGG, aged 25-71 (median 57), were re-irradiated due to tumor progression between 2011 and 2014. All patients underwent neurosurgery at the time of primary diagnosis (2008-2012). Pathology was: anaplastic astrocytoma G3 in 2 patients, and glioblastoma G4 in 31 patients. The surgery was followed by concurrent radiochemotherapy with temozolomide. All patients completed the treatment receiving 60 Gy. During followup gadolinium-enhanced MRI was performed every 3 months. Recurrence was found in MRI scans 3-54 months