ESTRO 38 Abstract book

S674 ESTRO 38

malignancies and 1% of non-Hodgkin lymphomas (NHL). Prognosis is generally poor with a median survival of less than 3 months if untreated. Standard of care for PCNSL is upfront high-dose methotrexate-based chemotherapy, with or without whole brain radiotherapy (WBRT). However, in recent years, the role of WBRT in a primary management has been questioned due to its toxicity and lack of convincing data for survival benefit. Even its role in a palliative setting remains to be clearly elucidated. In this retrospective study, data on WBRT for patients who are ineligible for systemic therapy were analyzed and correlated to patient outcomes, compared to the Patients diagnosed with PCNSL between 2002 and 2017 were selected. Patients were excluded if they received systemic therapy or focal radiation only. Data on patient demographics and WBRT (total dose, fractionation, tumor biologically effective dose [a/b=10, BED 10 ]) were collected and correlated with clinical outcomes. Survival curves were generated with the Kaplan-Meier method and compared using the log-rank test. Multivariate analysis was performed where prognostic variables and patient outcomes were correlated with the Cox proportional hazard model. Results A total of 48 patients were selected for analysis. Median age at diagnosis was 74 years (range 30-89 years) and median follow up among survivors was 4.4 years. The majority (85.4%) of tumors were identified as diffuse large B-cell lymphoma (DLBCL) on histology. Among all patients, 29 (60.4%) patients completed WBRT, 2 (4.2%) patients did not complete WBRT and 17 (35.4%) patients received no treatment. Median time interval between diagnosis and WBRT was 34 days (range 7-359 days). Median overall survival (OS) was 4.4 months. Patients who received WBRT had significantly better OS (8.8±1.8 months) compared to those with no WBRT (3.3±1.0 months) (p=0.003). In multivariate analyses, the addition of WBRT was associated with improved OS (hazard ratio [HR] 0.37, 95% CI 0.18-0.76, p=0.006). Among patients who received WBRT, whole brain dose higher than 30Gy was not associated with survival outcomes (p=0.43). However, a higher dose (35Gy, p=0.051) and BED 10 (45Gy, p=0.017) to gross tumor were associated with improved OS. Conclusion PCNSL patients who are ineligible for systemic therapy may still benefit from WBRT with a significant improvement in survival outcomes, compared to the best supportive care. Dose escalation through the addition of a gross tumor boost in these patients was associated with an improved overall survival. Future prospective studies are necessary to test the validity and confirm the significance of our study results. EP-1222 Simultaneous Integrated Boost in Anaplastic Astrocytoma: a propensity score matching analysis W.C. You 1 , C. Chen 1 , J. Lin 1 1 Taichung Veterans General Hospital, Department of Radiation Oncology, Taichung City, Taiwan Purpose or Objective Local recurrence remains a major cause of disease progression in anaplastic astrocytoma (AA). Escalation of radiation dose may leads to better results. The aim of this study is to evaluate the impacts of temozolomide chemoradiation with simultaneous integrated boost (CCRT-SIB) on clinical outcomes in the AA patients. Material and Methods We retrospectively searched all AA patients who had received surgical resection followed by chemoradiation in our institute from September 2004 to June 2015. Exclusion criteria is histology of oligodendroglioma or the oligodendroglial component was >10%. In CCRT-SIB protocol, a field-in-field escalation of 2.3 Gy per fraction supportive care only. Material and Methods

Purpose or Objective The treatment of recurrent high-grade glioma (HGG) is challenging. Various treatments including salvage stereotactic radiotherapy (SRT), salvage surgery, bevacizumab (BEV) or chemotherapy are used, but optimal treatment strategy is still unknown. We reviewed patients with recurrent HGG treated with salvage SRT to analyze feasibility, safety and prognostic factors. Material and Methods We retrospectively analyzed patients with histologically proven recurrent HGG who received salvage SRT from October 2007 to February 2018 at our hospital. Patients younger than 18 years old or who received no follow-up MRI were excluded. Overall survival (OS) and progression- free survival (PFS) were calculated by Kaplan-Meier method from the start date of salvage SRT. Cox proportional hazard model was used for multivariate analysis. Toxicity was evaluated by CTCAE version 4.0. A p-value<0.05 considered to be significant. Results A total of 86 eligible patients were identified. Patient characteristics were as follows; male/female=54/32, median age 52 years old (range, 19-88), latest WHO grade before salvage SRT III/IV=29/57. Initial recurrence pattern was local/diffuse/distant/multiple=46/22/6/12. Clinical target volume was defined as only contrast-enhancing lesion for 27 patients, and contrast-enhancing lesion and high-intensity area on fluid-attenuation inversion recovery image for 59 patients. Median interval between initial radiation and initial recurrence was 12.2 months (range, 1.0-447.3). Median planning target volume was 40.8cc (range, 1.4-491.1). Median prescribed dose of salvage SRT was 25Gy (range, 22.5-35Gy). BEV was administered to 70 patients, of which 51 patients was BEV naïve at salvage SRT and 19 patients were BEV failed at salvage SRT. Median follow-up period was 8.1 months from the start date of salvage SRT. The median OS was 10.4 months (95% confidence interval [CI]: 8.8-12.8) and the median PFS was 6.5 months (95% CI: 4.6-8.3). By multivariate analysis, more than 1 year interval between initial radiation and initial recurrence (HR 0.44, 95% CI: 0.25-0.79, p<0.01) and BEV naïve at salvage SRT (HR 0.37, 95% CI: 0.18-0.75, p<0.01) were identified as favorable factors of OS. Diffuse pattern at initial recurrence (HR 2.35, 95% CI: 1.18-4.68, p=0.04) and WHO grade IV (HR 2.26, 95% CI: 1.20-4.28, p=0.01) were unfavorable factors for OS. Diffuse pattern at initial recurrence (HR 1.80, 95% CI: 1.02-3.17, p=0.04) and WHO grade IV (HR 1.78, 95% CI: 1.05-3.01, p=0.03) were unfavorable factors for PFS. Grade 2 or higher radiation necrosis developed in 7 patients. Six of them were improved with corticosteroid or BEV but 1 patient required surgery. Conclusion Salvage SRT was feasible and safe treatment for recurrent HGG. Further prospective trials are needed to determine optimal sequencing or combination with BEV. EP-1220 Initial Clinical Experience of Carbon Ion Re- Irradiation of Recurrent High-Grade Glioma EP-1221 Palliative cranial irradiation improves survival in PCNSL patients ineligible for systemic therapy J. Song 1 , R. Samant 1 , X.Y. Fan 2 , M. Jay 3 , H. Chaudry 3 , D. MacDonald 3 , I. Bence-Bruckler 3 , V. Nair 1 1 The Ottawa Hospital, Radiation Oncology, Ottawa, Canada ; 2 The Ottawa Hospital, Pathology and Laboratory Medicine, Ottawa, Canada ; 3 The Ottawa Hospital, Hematology, Ottawa, Canada Purpose or Objective Primary central nervous system lymphoma (PCNSL) is a very rare type of cancer representing only 3% of all CNS Abstract withdrawn