Abstract Book

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ESTRO 37

primary treatment modality in an attempt to prevent neurocognitive dysfunctions induced by whole-brain radiotherapy (WBRT). However, single-dose radiosurgery also seems inadequate for treating large brain metastases or lesions close to critical structures in order to prevent adverse side effects. HFSRT appears a treatment option. Optimal dose and fractionation have yet to be established. The purpose of this study is to analyze our initial experience in treating brain metastases with HFSRT. Material and Methods 50 brain metastases > 3cm or located in critical areas were treated from October 2011 to December 2016 with HFSRT. Three fractionations were used: 10x4Gy(n=40), 5x6Gy(n=4), 5x7Gy(n=6). Contouring was based on MRI and CT fused images. We used a noninvasive frame-based mask, 6D coach, ExacTrac image guided system and IMRT or 3D planning. Results After a median follow-up of 6,4 months (1,4-21,7) 48 metastases (96%) achieved local control and 2 (4%) were considered radionecrosis versus progression still awaiting for a follow up MRI. Based on histology, there were 24 breast, 13 lung and 13 other cancers. 9(17%)patients developed distant brain metastases after a median of 3 months. Six of them were treated with WBRT and the remaining 3 with local radiotherapy.12 patients (24%) died during follow-up. Any patient developed >grade 2 toxicity related to radiation Conclusion With lack of longer follow-up, our experience with large and critical brain metastases showed that HFSRT is an excellent alternative with very good local control and tolerance. S.H. Youn 1 , K.H. Cho 1 , J.Y. Kim 1 , B.R. Ha 1 , Y.K. Lim 1 , J.H. Jeong 1 , S.H. Lee 2 , H. Yoo 2 , H.S. Gwak 2 , S.H. Shin 2 , E.K. Hong 3 1 National Cancer Center, Proton Therapy Center, Goyang-si, Korea Republic of 2 National Cancer Center, Neuro-Oncology Clinic, Goyang- si, Korea Republic of 3 National Cancer Center, Department of Pathology, Goyang-si, Korea Republic of Purpose or Objective To investigate the clinical outcome of proton therapy (PT) in patients with chordoma Material and Methods Fifty eight patients with chordoma treated with PT between June 2007 and December 2015 at National Cancer Center, Korea were retrospectively analyzed. The median total dose was 69.6 CGE (range, 64.8-79.2). Local progression free survival (LPFS), distant metastasis free survival (DMFS), overall survival (OS), and disease specific survival (DSS) rates were calculated by Kaplan-Meier method. Results The median follow-up duration was 42.8 months (range, 4-174). The 5-year LPFS and DMFS rates were 87.9%, and 86.7%, respectively. The location of tumor was associated with the risks of local progression; the 5-year LPFS rates were 97.0% for the skull base tumors vs. 57.1% for the cervical spine tumors (p=0.020) vs. 86.5% for the sacral tumors (p=0.105, when compared with the cervical spine tumors). Initial tumor size (< 5cm vs. ≥ 5cm in maximum diameter) was associated with the risk of distant metastasis (the 5-year DMFS rates; 100.0% vs. 59.5%, p=0.001, respectively), but was not significantly associated with the risks of local progression (5-year LPFS rates; 87.7% vs. 88.0%, respectively, p=0.712). The total dose (< 69.6 CGE vs. ≥ 69.6 CGE) was associated with the risks of both local progression and distant metastasis (the EP-1196 Clinical outcome of proton therapy for patients with chordomas

5-year LPFS; 63.5% vs. 92.8%, respectively, p=0.050, and the 5-year DMFS; 58.3% vs. 95.0%, respectively, p=0.016). The 5-year OS and DSS rates were 88.3% and 92.9%, respectively. None had greater than grade 3 acute toxicity, 3 patients had grade 3 late toxicity (skin and subcutaneous toxicity (n=1), sacral plexopathy with skin and subcutaneous toxicity (n=1), and right hemiparesis due to brain stem edema (n=1)) with none of ≥ grade 4. Conclusion PT is effective and safe treatment in patients with chordomas. Further investigation is warranted to improve the outcome of those with cervical spine chordomas, potentially with intensity modulated PT. EP-1197 Clinical outcomes for Chordomas treated with Radical Radiotherapy: A Single Institutional Analysis J. O'Shea 1 , G. Rangaswamy 2 , A.M. Glynn 2 , M. Dunne 3 , R. Grogan 4 , S. McNally 4 , O. Boychak 2 , D. Fitzpatrick 2 , C. Faul 2 1 St Luke's Radiation Oncology Center, Radiation Oncology, Dublin, Ireland 2 Ireland, , 3 Dublin, Ireland, 4 Department of Neurosurgery, Department of Neurosurgery, Dublin, Ireland Purpose or Objective Chordomas are rare, constituting 0.2% of CNS tumours and 2-4% of primary bone neoplasms, commonly found in the sacrum, clivus, and along the spinal axis. The aim of this study is to assess whether a combination of intensity modulated radiotherapy (IMRT) +/- stereotactic boost allowed safe escalation of radiotherapy (RT) dose to that seen in proton studies and to evaluate clinical outcomes. Material and Methods A retrospective analysis of 17 patients with histologically proven chordomas treated at our institution with radical RT between January 2011 to January 2017 was carried out. Patients who had; palliative RT (n=1), no treatment data available (n=4), or received RT outside our institution (n=1) were excluded. Results Eleven patients were included in the study, 8 skull-base and 3 vertebral chordomas. Fifty-five percent (n=6) female and 45% male. Median age at diagnosis was 42 (range 28-68 years). Median follow-up time in skull-base group was 24.5 months (range 4-49) and 15.5 months (range 8-35) in the vertebral group. Median RT dose in the skull-base group was 64 Gy (range 54-78 Gy) and 66 Gy (range 50 –74 Gy) in the vertebral group. The median time from diagnosis to RT start was 5.7 months for the 2 patients who progressed compared to 2.7 months for those who did not progress (p= .218). This was predictive of local control. Mean optic chiasm max dose was 54.8Gy (50-59.9Gy), mean right optic nerve (ON) max dose 41.9 Gy(7.7 – 63.7Gy), mean left ON max dose 57.55 Gy (54.7- 59.7Gy) and mean brainstem max dose was 60.4 Gy (54.1- 71Gy). Four patients with skull-base chordomas were considered for a stereotactic boost, 3 patients received it, median dose 10.8Gy (range 9-43.2Gy), 1 did not due to lack of residual disease to target after IMRT. Acute toxicity ( n = 9, 82% of all patients) occurring within 3 months of RT start was more commonly reported than late toxicity ( n = 3, 27%). Acute toxicities included grade 1 cranial neuropathy ( n = 1), grade 2 mucositis ( n = 2), grade 1-2 fatigue ( n = 3) and grade 1 peripheral neuropathy ( n = 1). Late grade 2 cranial neuropathy and grade 1 peripheral neuropathy persisted in 1 skull base and 1 vertebral patient at 1 year, respectively. One- year progression free survival (PFS) was 87.5% and 1 year overall survival (OS) was 87.5%. Two year PFS was 72%. Three-year OS was approximately 70%. In total, 1 patient with vertebral chordoma progressed locally and required further palliative RT and subsequently died. Another vertebral chordoma patient died 23 months following