ESTRO 36 Abstract Book

S262 ESTRO 36 2017 _______________________________________________________________________________________________

Montreal, Canada 4 McGIll University Health Center, Clinical Statistics, Montreal, Canada 5 McGIll University Health Center, Medical physics, Montreal, Canada 6 McGIll University Health Center, Pathology, Montreal, Canada Purpose or Objective The role of adjuvant radiotherapy (RT) in the post- operative management of atypical meningiomas remains controversial, particularly after a gross total resection (GTR). In this study, we reviewed long-term results in such patients aiming to identify patient-, tumor- or treatment- related variables potentially associated with prognostic significance that might influence outcomes. Material and Methods Between 1992 and 2013, we retrospectively identified 72 patients with atypical meningioma treated at our institution. All of them underwent a maximal safe surgical resection. Patients with multiple tumors, neurofibromatosis type 2, previous cranial RT, multiple lesions, previously resected grade I lesion that had transformed to a grade II at time of recurrence or inadequate follow-up imaging were not eligible. Pathology was reviewed in each case to confirm grading. We performed pre- and post-operative serial planimetric and volumetric measurements of tumor size changes from magnetic resonance imaging. Age, tumor location, bone involvement, extent of resection, tumor growth rate, use of post-operative radiotherapy (PORT), and residual tumor volume at time of radiotherapy (RT) were assessed by uni- and multivariate analysis to determine their influence on local tumor progression. We measured, before and after RT, absolute and relative tumor growth rates and tumor doubling time in all patients. Results Median age was 62 years and the median follow-up was 69 months. Forty-two patients (58%) underwent GTR and 30 (42%) underwent a subtotal resection (STR). PORT was delivered to 12 patients (28.5%) with GTR and only 4 (13%) with subtotal resection (STR). Control rates at 5 years for GTR patients with or without PORT were 100% vs. 53% (median time for failure = 30 months), respectively (p=0.0034). Similarly, local control for STR patients +/- PORT were 75% vs 4% (median time for failure = 10 months), respectively (p=0.0038). On multivariate analysis, no-PORT (p=0.01) and STR (p=0.0002) were the only independent significant prognostic factors for local recurrence. Based on Youden-Index-J, a cut-off residual volume of less than 8.76 cm 3 was associated with lower failure rate (7% vs 77 %, p<0.001). In patients not receiving RT, the median relative and absolute growth rates, and tumor doubling time were 115.75%/year, 4.27 cm 3 /year and 0.78 year, respectively. These indices improved after the addition of RT (74.5%/year, 2.48c cm 3 /year and 1.73 year, respectively). Volumetric measurement detected tumor progression earlier than planimetric by a median time lag of 18 months. Conclusion In patients with atypical meningioma, regardless of whether a GTR or STR is performed, the use of PORT appears to be associated with significant improvement in local disease control. Patients with a residual tumor larger than 8.76 cm 3 have an increased failure rate and should be considered for early RT. PV-0503 Novel RPA classification combining MGMT promoter methylation status in newly diagnosed glioblastoma C.W. Wee 1 , E. Kim 1 , I.A. Kim 1 , T.M. Kim 2 , Y.J. Kim 2 , C.K. Park 3 , J.W. Kim 3 , C.Y. Kim 3 , S.H. Choi 4 , J.H. Kim 4 , S.H. Park 5 , G. Choe 5 , S.T. Lee 6 , I.H. Kim 1 1 Seoul National University College of Medicine, Department of Radiation Oncology, Seoul, Korea

Republic of 2 Seoul National University College of Medicine, Department of Internal Medicine, Seoul, Korea Republic of 3 Seoul National University College of Medicine, Department of Neurosurgery, Seoul, Korea Republic of 4 Seoul National University College of Medicine, Department of Radiology, Seoul, Korea Republic of 5 Seoul National University College of Medicine, Department of Pathology, Seoul, Korea Republic of 6 Seoul National University College of Medicine, Department of Neurology, Seoul, Korea Republic of Purpose or Objective Since the prognostic and predictive value of MGMT promoter methylation is widely understood, a refinement of the recursive partitioning analysis (RPA) classification for glioblastoma (GBM) integrating the MGMT methylation status is warranted. Material and Methods A total of 256 patients since 2006 were prospectively intended to be treated with radiotherapy (RT) plus concurrent and adjuvant temozolomide (TMZ) according to the standard regimen and the MGMT methylation status was available in all patients. In 45.3 % of the patients, the MGMT promoter was methylated. Results The median follow-up and survival (MS) were 17.7 and 19.6 months, respectively. RPA was performed based on the results of multivariate analysis, and in contrast to the RTOG RPA classification, Karnofsky performance status (KPS) score made the initial split (≥70 vs. <70). Four RPA classes were identified ( p < .001); class I, KPS≥70/GTR/methylated MGMT (MS 69.2 months); class II, KPS≥70/GTR/non-methylated MGMT or KPS≥70/residual disease/methylated MGMT (MS 23.7 months); class III, KPS≥70/residual disease/non-methylated MGMT (MS 15.4 months); class IV, KPS<70 (MS 11.0 months). Conclusion A novel RPA classification for GBM was formulated highlighting the significance of MGMT promoter methylation in the TMZ era. This model integrating pertinent molecular information can be used effectively for the prediction of individual patient’s prognosis. PV-0504 Observed survival in 3270 patients treated with Whole Brain Radiotherapy compared to the QUARTZ data P. Jeene 1 , R. Kwakman 1 , J. Van Nes 2 , K. De Vries 3 , G. Wester 4 , E. Dieleman 1 , T. Rozema 5 , J. Zindler 6 , J. Verhoeff 7 , L. Stalpers 1 1 Academic Medical Center, Radiotherapy, Amsterdam, The Netherlands 2 Radiotherapeutisch Instituut Friesland, Radiotherapy, Leeuwarden, The Netherlands 3 Antoni van Leeuwenhoek, Radiotherapy, Amsterdam, The Netherlands 4 Radiotherapiegroep, Radiotherapy, Arnhem, The Netherlands 5 Instituut Verbeeten, Radiotherapy, Tilburg, The Netherlands 6 MAASTRO Clinic, Radiotherapy, Maastricht, The Netherlands 7 Academic Medical Center Utrecht, Radiotherapy, Utrecht, The Netherlands Purpose or Objective Since Horton et al (1971), Whole Brain RadioTherapy (WBRT) is considered the standard of care for patients with more than 3 brain metastases or patients otherwise unfit for radical local treatment and with at least a reasonable performance score. In the 2016 QUARTZ trial, patients with brain metastases from a primary non-small cell lung cancer (NSCLC) were randomized between best supportive care (BSC) and WBRT with BSC. There was no