ESTRO 38 Abstract book

S382 ESTRO 38

three consecutive days. Cumulative incidence analysis was used to compare local control (LC), distant brain failure (DBF), and radiation-induced brain necrosis (RN) between groups from the time of SRS. Results At a median follow-up of 13 months, median OS and 1- year survival rates were comparable: S+fSRS, 13.5 months and 59%; fSRS, 15.2 months and 68% ( p =0.2). Median DBF did not differ significantly, being 12 and 14 months for S+fSRS and fSRS, respectively. Eighteen patients undergoing S+fSRS and 17 patients treated with fSRS recurred locally ( p =0.4). Six-month and 1-year LC rates were 92% and 85% in S+fSRS group and 96% and 91% in fSRS group, respectively ( p =0.1). Stable extracranial disease, systemic therapy with TKIs, a single brain metastasis, adenocarcinoma histology and KPS >70 emerged as significant independent indices of prolonged OS. Controlled extracranial disease and TKI therapy resulted to be the most significant independent prognostic factors. Conclusion In conclusion, fSRS is an effective treatment option for large NSCLC brain metastases, resulting in a similar local control and reduced risk of RN compared to S+fSRS. PO-0746 The utility of functional magnetic resonance imaging in target delineation of high-grade gliomas L. Qian 1 , Q. Fei 1 , Y. Zhang 1 , W. Guo 1 , X. Bian 1 , L. Yin 1 , P. Yan 1 , T. Wang 1 , P. Qian 1 , Z. Guo 2 , X. He 1 1 Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated Cancer Hospital of Nanjing Medical University, Department of Radiation Oncology, Nanjing, China ; 2 Jiangsu Cancer Hospital & Jiangsu Institute of Cancer Research & The Affiliated Cancer Hospital of Nanjing Medical University, Department of Radiology, Nanjing, China Purpose or Objective This study explored the different survival outcomes and failure patterns of high-grade glioma (HGG) patients by comparing the combination of functional imaging technology (fMRI: perfusion weighted imaging (PWI), diffusion-tensor imaging (DTI)) and contrast-enhanced MRI (CE-MRI) imaging (enhanced T1) with CE-MRI alone in guiding the delineation of radiotherapy target area. Material and Methods 102 patients with postoperative HGG between 2012 and 2016 were included in our study. All patients were treated with IMRT in combination with the standard STUPP regimen. MRI (plain scan + enhancement), MR spectroscopy (MRS), DTI and PWI were performed before radiotherapy for postoperative patients. 50 (cohort A) were delineated based on fMRI (PWI, DTI) and CE-MRI (enhanced T1). The other 52 (cohort B) were delineated based on CE-MRI (enhanced T1, FLAIR/T2) as controlled. Survival analysis was performed using the Kaplan–Meier method, and the difference between two groups were evaluated by log-rank test. p <0.05 was considered statistically significant. Results All clinical characteristics were comparable between the two cohorts. At a median follow-up of 20 mouths, 80 (78%) patients had died. The median survival benefit was 6 months. The median survival was 24 months in cohort A and 18 months in cohort B. The 2-year OS, PFS, and LRC rates were 48% vs 25% ( p = 0.005), 42% vs 13.46% ( p = 0.0003), and 40% vs 13.46% ( p = 0.0007) for cohort A and cohort B, respectively. Two cohorts had similar rates of disease progression and recurrence （ 62% vs 63.5%, p = 0.879 ） , while the proportion of failure patterns was different. In cohort A, 28 (90.3%) patients experienced recurrence within the irradiated field (50-60Gy); 4 (9.7%) experienced out-field failure (2 cases of marginal failure, 1 case of pituitary metastasis, 1case of cerebrospinal fluid metastasis). In cohort B, 26 (78.8%) patients experienced

that FSRT was used for large lesions and adverse locations, we find that FSRT can particularly be beneficial for patients with large lesions or lesions located near critical structures. Further investigation is warranted to determine the optimal dose/fractionation. PO-0744 Efficacy of single-fraction or fractionated SRS combined with CPIs in melanoma brain metastases G. Minniti 1 , D. Arzellini 2 , C. Reverberi 2 , F. Bianciardi 1 , B. Tolu 1 , C. Scaringi 1 , M. Osti 2 , P. Gentile 1 1 UPMC San Pietro FBF, Radiation Oncology, Roma, Italy ; 2 Sant’ Andrea Hospital- University Sapienza- 00100 Rome, Radiation Oncology, Rome, Italy Purpose: to investigate efficacy and safety of concurrent stereotactic radiosurgery (SRS), either single-fraction SRS s-fSRS; 18-22 Gy) or fractionated (fSRS; 3x9 Gy) SRS and ipilimumab or nivolumab in patients with untreated melanoma brain metastases. Patients and Methods: Eighty consecutive patients with 326 melanoma BM, receiving SRS in combination with ipilimumab or nivolumab, were analyzed. Concurrent systemic treatment was generally started within 5 days before SRS and consisted of intravenous nivolumab or ipilimumab until disease progression or inacceptable toxicity. Primary endpoint of the study was intracranial progression-free survival (PFS). Secondary endpoints were extracranial PFS, overall survival (OS), and toxicity. Results: Eighty patients were analyzed. Forty-five patients received SRS and ipilimumab (SRS+ipilimumab), and 35 patients SRS and nivolumab (SRS+nivolumab). With a median follow-up of 15 months, the 6-month and 12- month intracranial PFS rates were 69% (95%CI,54-87%) and 42% (95%CI,24-65%) in SRS+nivolumab group and 48% (95%CI,34-64%) and 17% (95%CI,5-31%) in SRS+ipilimumab group (p=0.02), respectively. Similarly, patients treated with SRS and nivolumab had better 6-month extracranial PFS and 12-month OS (SRS+nivolumab, 57% and 37%; SRS+ipilimumab, 42% and 17%). Stratification for type of SRS showed that combined CPIs and fSRS were associated with better intracranial PFS; 6-month and 12-month rates were 70% and 40%, respectively, for patients receiving fSRS and 46% and 10%, respectively, for those undergoing sf-SRS ( p =0.01). As for intracranial PFS, fSRS resulted in better extracranial PFS. Grade 3 treatment-related adverse events occurred in 24% of patients receiving SRS and ipilimumab and 17% of patients receiving SRS and nivolumab. Conclusions: In conclusion, concurrent SRS and CPIs show meaningful intracranial activity and acceptable toxicity in patients with either asymptomatic and symptomatic melanoma BM, particularly when fSRS is combined with nivolumab. Further studies need to investigate the potential stronger synergistic effect of fractionated radiation schedules and CPIs. PO-0745 Fractionated SRS (fSRS) or surgery plus fSRS to resection cavity for NSCLC large brain metastases G. Minniti 1 , C. Scaring 1 , D. Arzellini 2 , F. Bianciardi 1 , B. Tolu 1 , R. Morace 3 , M. Osti 2 , P. Gentile 1 1 UPMC San Pietro FBF, Radiation Oncology, Roma, Italy ; 2 Sant’ Andrea Hospital- University Sapienza, Radiation Oncology, Roma, Italy ; 3 IRCCS Neuromed-, Neurosurgery, 86077 Pozzilli IS, Italy Purpose or Objective T o investigate clinical outcomes in patients with NSCLC brain metastases <4 cm in size undergoing complete surgical resection plus fractionated stereotactic radiosurgery to the resection cavity (fSRS) or fSRS alone. Material and Methods Two hundred and twenty-seven patients with 246 brain metastases receiving surgery plus fSRS (S+fSRS) or fSRS alone were analyzed. All lesions evaluated in the study were treated with a dose of 27 Gy given in 3 fractions over