ESTRO 38 Abstract book

S379 ESTRO 38

Y. Koide 1 , T. Kodaira 1 , H. Tachibana 1 , H. Tanaka 1 , N. Tomita 2 1 Aichi Cancer Center, Radiation oncology, Nagoya, Japan ; 2 Nagoya City University Graduate School of Medical Sciences, Department of Radiology, Nagoya, Japan Purpose or Objective Large brain metastases (BM) are associated with limited local control and neurotoxicity. Some recent studies reported that hypofractionated stereotactic radiotherapy (HFSRT) is a reasonable option for such tumors, relative to single-fraction therapy. We evaluated the efficacy and the safety of HFSRT for BM larger than 2 cm. Material and Methods From 2006 to 2016, 61 patients with BM larger than 2 cm were treated with HFSRT in our institution. The exclusion criteria were: (1) no available magnetic resonance imaging or computed tomography, (2) prior brain radiotherapy or surgery, and (3) combination with whole brain radiotherapy. All patients were treated using helical tomotherapy. The planning target volume (PTV) was set as the gross tumor volume plus a 2-mm margin in all dimensions. The prescription dose was 35 Gy in 5 fractions, and assigned to the 90% isodose surface used PTV coverage of 95%, normalized to 100% dose at the isocenter. Eligible patients were divided according to maximum BM diameter (group A [23 patients]: ≥3 cm, group B [22 patients]: <3 cm) to assess the relationship between tumor size and prognosis or safety. The primary endpoint was local control rate (LCR), and secondary endpoints were response rate (RR), brain progression-free survival (BPFS), median survival time (MST), and radionecrosis (RN). Univariate and multivariate analyses for LCR were conducted using Cox’s proportional hazards A total of 45 patients with 58 lesions were eligible in this study. All patients completed planned HFSRT schedule without delay or discontinuation. At the last follow-up, 7 patients (15.6%) were alive, 34 patients (75.6%) had died, and 4 patients (8.9%) were lost to follow-up. The median follow-up period for all patients were 11.3 months (range: 1.7-93.9 months) and 15.2 months (range: 6.9-93.9 months) among patients who had not died. The median tumor volume for all lesions was 19.3 mL (range: 6.21- 115.4 mL). The RR was 86.4% with an overall LCR of 64.7% at 12 months (67.1% for group A and 61.5% for group B [p = 0.45]). The median BPFS and MST were 11.6 and 14.2 months, respectively. Univariate analyses revealed that female patients and gynecological cancer patients had poorer LCR, but they were not significantly independent prognostic factors in multivariate analyses (p = 0.06, 0.09, respectively). Two patients with breast cancer experienced RN (4.4%). One patient (group A) underwent resection 5 years after the HFSRT, and the other patient (group B) underwent resection 6 years after HFSRT. Conclusion HFSRT is safe for large BM but further studies are needed to determine optimal doses and fractions. PO-0738 Extent of resection is potent prognostic factor next to molecular subtype in low-grade glioma J. Choi 1 , S.H. Kim 2 , J.H. Chang 3 , S.H. Park 1 , C. Suh 4 1 Jeju National University Hospital, Radiation Oncology, Jeju, Korea Republic of ; 2 Yonsei University College of Medicine, Pathology, Seoul, Korea Republic of ; 3 Yonsei University College of Medicine, Neurosurgery, Seoul, Korea Republic of ; 4 Yonsei University College of Medicine, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective We aimed to evaluate treatment outcomes and identify prognostic factors of low-grade glioma (LGG) patients according to the new 2016 WHO classification. Material and Methods model. Results

The record of 153 patients diagnosed as WHO grade II LGG between March 2003 and November 2015 were retrospectively reviewed. Based on the 2016 WHO classification, 80 patients (52.3%) had diffuse astrocytoma (DA), IDH mutant; 45 patients (29.4%) had oligodendroglioma (ODG), IDH mutant and 1p/19q codeleted; and 28 patients (18.3%) had DA, IDH wild-type. Results The median age at diagnosis was 41 years (range, 22-74). Gross total resection (GTR) was performed in 71 patients (46.4%), subtotal resection in 31 (20.3%), partial resection in 43 patients (28.1%), and biopsy in 8 patients (5.2%). One hundred two patients (66.7%) received postoperative radiotherapy (RT). The median follow-up time was 69.9 months (range, 5.3-171.3). The 5-year and 10-year progression free survival (PFS) were 72.7% and 51.5%, and 5-year and 10-year overall survival (OS) were 82.5% and 63.5%, respectively. GTR and molecular subtype of IDH mutant and/or 1p/19q codeletion were favorable prognostic factors for both PFS and OS. Patients with tumoral IDH wild-type had significantly decreased OS than those with IDH mutation and 1p/19q codeletion. Among patients with ODG underwent GTR, no failure was observed after RT. Patients with IDH mutant and wild-type performed non-GTR had high recurrent rates after RT (47.6% and 57.9%). Regarding OS, age (<40 years), tumor location (frontal lobe), chemotherapy, and RT were not significant prognostic factors on multivariate analysis. Conclusion Molecular classification in LGG was of prognostic relevance, with the tumors that do not have IDH mutations and/or 1p/19 codeletion having a particularly poor outcome regardless of treatment. The favorable results were observed in patients who undergone GTR. Prospective study is needed to demonstrate the role of adjuvant treatment in LGG. PO-0739 Sense and radiosensitivity – CyberKnife® stereotactic radiotherapy in patients with meningiomas. H. Grzbiela 1 , R. Tarnawski 1 , E. Nowicka 1 , M. Gawkowska 1 , S. Owczarek 1 , M. Stapor-Fudzinska 2 1 Centrum Onkologii-Instytut im.M.Sklodowskiej-Curie Warsaw, III Radiotherapy and Chemotherapy Clinic, Gliwice, Poland ; 2 Centrum Onkologii-Instytut im.M.Sklodowskiej-Curie Warsaw, Radiotherapy Planning Department, Gliwice, Poland Purpose or Objective The objective of the study was to assess the effects of CyberKnife ® stereotactic radiotherapy in patients diagnosed with meningiomas, and to evaluate, whether this technique, due to high conformality and steep dose fall-off, leads to a lesser degree of CNS toxicity, in particular concerning visual pathway toxicity. Material and Methods 157 patients diagnosed with meningiomas, aged 20 – 79 (median 54), were treated in our Clinic between 2011 and 2014. 43 patients (27.4%) underwent neurosurgery at the time of diagnosis (pathology was meningothelial or psammomatous meningioma WHO grade 1), but during follow-up recurrence or progression of the tumor was observed. For 114 patients (72.6%), in whom surgery was not possible (due to tumor location or poor performance status), radiation therapy was primary treatment. All patients underwent CyberKnife ® stereotactic radiation therapy. Tumor volume ranged from 1.5 to 37.5 cm 3 . Total dose received was 18 Gy (in 3 fractions), 21 Gy (in 3 fractions) or 16 Gy (in 2 fractions) – depending on tumor volume and location (especially in regard to the distance between tumor and visual pathway). Results All patients completed the treatment. 16 patients (10.2%) suffered from mild or moderate nausea (CTCAE grade 1 or 2), 37 patients (23.6%) reported headache CTCAE grade 1