Abstract Book

S682

ESTRO 37

Material and Methods We carried out a retrospective study of all patients with a histological diagnosis of GBM at a single institution between 2002 and 2015. We identified 11 patients who survived >3years from the date of diagnosis. The median survival of our cohort was 7.4yrs (89mths), ranging between 4.25 – 14.9 years. The histology of all 11 patients was reviewed independently by (AB) and were analysed for IDH1/ATRX/p53. Molecular analyses carried out included IDH 1R132H mutant, ATRX mutant and presence of p53. We recorded the presence of mitosis, necrosis and vascular proliferation as well as patient demographics including age at diagnosis, sex, tumour location and treatment received. Results Patients ranged in age between 24-70. 4/11 (36%) were >50yrs at diagnosis. All 11 patients underwent debulking surgery – 3/11 (27%) total and 8/11 (72%) subtotal based on post-operative MRI. 8/11 (72%) received full STUPP protocol, with 1 patient receiving 4 cycles of PCV. 1 patient had no chemotherapy. 6/11 (54%) of our long term survivors (LTS) were ATRX positive. 4/11 (36%) were IDH-1R132H positive. 4 patients (36%) were positive for both. All patients who were IDH1 positive were also ATRX positive. 9/11 (81%) showed p53 expression, 8 of which were strong and diffuse. All 4 patients above the age of 50 were IDH1 and ATRX negative. On analysing our data, none of our patients originally assigned GBM were found to have a lower grade on review of their histology. Conclusion Whilst the update in the WHO classification is a step in the right direction, more studies need to be carried out on long term survivors to assess whether a unique LTS profile can be attributed to these patients. Over half of the patients in our group were ATRX mutant positive but only 4/11 had IDH-1 mutation in addition. We postulate that further formal genotyping in the form of genetic sequencing to test for sub varieties in IDH, as well as MGMT and 1p19q testing is required in order to further analyse our cohort of patients. Work in this area is still on-going and final results will be updated. EP-1231 Cyberknife Robotic Radiosurgery for Bilateral Acoustic Schawanomas-HCG experince S. Papaiah Susheela 1 , M. N 1 , R. Krishnappa 1 , A. GH 1 , P. Kumar Marimuthu 1 , P. Kumar Karumanchi 1 , A. P 1 , M. Gupta 2 , R. Deshpande 3 , S. Gopal 4 , S. Rudrappa 4 , P. G 5 , I. Desai 6 , J. A 7 , A.K. BS 1 1 Health Care Global Enterprises Ltd, Cyberknife- Radiation oncology, Bangalore, India 2 Health Care Global Enterprises Ltd, Anaesthesia, Bangalore, India 3 Fortis Hospital, Neurosurgery, Bangalore, India 4 Sakra Hospital, Neurosurgery, Bangalore, India 5 Health Care Global Enterprises Ltd, Nuclear medicine, Bangalore, India 6 Health Care Global Enterprises Ltd, Radiology, Bangalore, India 7 Health Care Global Enterprises Ltd, Physics, Bangalore, India Purpose or Objective Vestibular schwannomas account for approximately 8 percent of intracranial tumors in adults and 80 to 90 percent of tumors of the cerebellopontine angle (CPA). The overall incidence of vestibular schwannomas is about one per 100,000 person-years. The tumors are unilateral in more than 90 percent of cases , affecting the right and left sides with equal frequency. Bilateral vestibular schwannomas are primarily limited to patients with neurofibromatosis type 2. Treatment options of acoustic schwannomas are surgery, radiation and observation. Treatments of bilateral schwannomas are challenging. Usually treatment is done sequentially to prevent toxicity.To assess the safety,efficacy and quality of life in

Medical Research Centre, Neurooncology, Saint- Petersburg, Russian Federation

Purpose or Objective The aim of this study was to analyze early radiological response of melanoma brain metastases to Gamma Knife radiosurgery (GKRS) as a function of volume changes with time and to reveal a possible correlation between tumor radioresponsiveness and patient clinical outcomes. Material and Methods We carried out a retrospective review of 78 patients treated with GKRS for melanoma brain metastases between 2009 and 2015 and subjected to follow-up MRI examinations. Radiosurgery was performed with Leksell Gamma Knife 4C and Perfexion (Elekta AB, Sweden). The patients underwent control MRI with standard protocols at regular 2-3-month intervals. MR images were analyzed with Gamma Plan software. All metastatic tumors in each patient were included in volumetric analysis (298 in total). Volumetric measurements of metastases on pre- and initial post-treatment images were performed in order to calculate the tumor volume changes with time. We divided the patients into two groups according to radioresponsiveness and compared survival, local control and appearance of new metastases in the brain in these groups with the log-rank test as well as performed univariate and multivariate analyses to reveal significant predictors of outcomes. Results We found that radioresponsivness of melanoma brain metastases to GKRS differed considerably. One group of tumors underwent rapid shrinkage, whereas the other showed minor fluctuations in volume. To formalize this observation we introduced a new parameter – tumor dynamic index (TDI) which reflected the tumor radioresponsiveness. Tumors with a slow response had TDI ≤ 25, whereas tumors with a rapid shrinkage TDI > 25. Local recurrences were observed in 6% of tumors with TDI ≤ 25 and in 11% of tumors with TDI > 25. New metastases in the brain were diagnosed earlier for patients with TDI ≤ 25 than those with TDI > 25 (8.6 months vs 2.7 months, respectively). Median overall survival was 15.2 months for patients with a slow response and 6.3 months for those with a rapid response. After univariate and multivariate analyses, TDI, KPS and systemic disease status remained significant predictors of survival, whereas TDI, number of brain metastases and systemic disease status associated with the appearance of new metastases in the brain. Conclusion Melanoma brain metastases showed different radio- responsiveness to radiosurgery. Rapid shrinkage of brain metastases is associated with poor prognosis, which may indicate more aggressive biological behavior of this tumor subtype. EP-1230 Molecular Markers as a predictor of Long-term survival in patients with Glioblastoma Multiforme E. Connolly 1 , A. Beausang 2 , C. Faul 1 1 St Luke's Radiation Oncology Network, Beaumont Centre, Dublin, Ireland 2 Beaumont Hospital, Department of Pathology, Dublin, Ireland Purpose or Objective Glioblastoma multiforme (GBM) is the most common and aggressive adult primary brain cancer, with <10% of patients surviving for more than 3 years. Individual molecular biomarkers have been postulated to result in better survival in GBM patients along with patient and treatment characteristics. Recently, the 2016 update in WHO classification included molecular parameters in the diagnostic schema which may be more relevant to outcome than histological grading alone.