ESTRO 2020 Abstract Book

S192 ESTRO 2020

1 Klinikum rechts der Isar- TU München, Department of Radiation Oncology, München, Germany ; 2 Klinikum rechts der Isar- TU München, Department of Neurosurgery, München, Germany ; 3 Klinikum rechts der Isar- TU München, Department of Neuropathology, München, Germany ; 4 Klinikum rechts der Isar- TU München, Department of Neurologie, München, Germany Purpose or Objective Elderly patients with newly diagnosed glioblastoma (GBM) are currently recommended to undergo adjuvant treatment with either normo- or hypofractionated radiotherapy, with or without concomitant and adjuvant chemotherapy. The concrete treatment recommendation is based on the age, the MGMT promotor methylation as well as the performance status. None of these factors is weighted against others. We designed a risk-score to classify elderly GBM patients for their prognosis after histological confirmation. Material and Methods 181 GBM-patients, 65 years or older were retrospectively analyzed. Clinical characteristics, such as age, KPS, motor function as well as aphasia before and after surgery, the extent of resection as well as the MGMT methylation status were analyzed for their impact on the overall survival (OS). Factors which were significant in univariate analysis (log- rank-test, p<0.05) were included in a multivariate model (multivariate cox-regression analysis, MVA). Significant factors (p<0.05) from this model were included in a prognostic score. Results The Age, KPS, MGMT-status, extent of resection, aphasia after surgery and motor-dysfunction after surgery were significantly associated with OS on univariate analysis (p<0.05). On MVA three factors were significant: age (p 0.002), MGMT promotor methylation (p 0.013) and Karnofsky performance status (p 0.005). The resulting score was based on Age (5 points 65 to <70 years, 4 for 70 to <75 years, 3 for 75 to <30 years, 1 for >80 years), KPS (4 points for 100-70%, 2 points for 50-60% and 0 point for <50%) and MGMT-Status (3 for unmethylated or unknown, 5 for methylated). Two groups could be divided, group A (4 to 8) with a median OS of 2.7 months and group B (9 - 14) with a median OS of 7.8 months (Figure1, Kaplan Meier curves for the Elderly-Score with a threshold of 8). The score was of prognostic significance, independently from the adjuvant treatment regimen.

Conclusion We generated a score, which distinguishes patients with a poor prognosis from patients with a better prognosis. Inclusion of the score in future retro- or prospective trials could help to enhance the comparability of the results. Before its use in daily routine, external validation is recommended. PH-0359 Blood plasma based risk stratification of glioblastoma patients D. Fleischmann 1,2,3 , K. Unger 1,4,5 , V. Ruf 6 , T. Heider 4,5 , J. Hess 1,4,5 , G. Drexler 1 , J. Herms 6 , N. Thon 2,7 , F. Kreth 2,7 , J. Tonn 2,7 , H. Zitzelsberger 1,4,5 , K. Lauber 1,2,5 , C. Belka 1,2,5 , M. Niyazi 1,2,5 1 University Hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany ; 2 German Cancer Consortium DKTK, partner site Munich, Munich, Germany ; 3 German Cancer Research Center DKFZ, Deutsches Krebsforschungszentrum, Heidelberg, Germany ; 4 Helmholtz Zentrum München, Research Unit of Radiation Cytogenetics, Neuherberg, Germany ; 5 Helmholtz Zentrum München, Clinical Cooperation Group Personalized Radiotherapy in Head and Neck Cancer, Neuherberg, Germany ; 6 Faculty of Medicine- LMU Munich, Institute of Neuropathology, Munich, Germany ; 7 University Hospital- LMU Munich, Department of Neurosurgery, Munich, Germany Purpose or Objective Risk stratification in IDH-wildtype glioblastoma patients is limited, as MGMT methylation status is the only prognostically relevant biomarker available and no liquid biopsy markers are in clinical use. Recently, we established a prognostic miRNA signature in glioblastoma tumour tissue. Here, we prospectively analysed the 4- miRNA signature in blood plasma samples to assess its value as a prognostic liquid biopsy marker for glioblastoma patients. Material and Methods Glioblastoma patients with IDH-wildtype between 18 and 70 years of age with the indication for conventionally fractionated radiochemotherapy were enrolled prospectively. Blood plasma samples were obtained prior to radiochemotherapy and were examined using miRNA microarrays on the expression levels of the four miRNAs hsa-let-7a-5p, hsa-let-7b-5p, hsa-miR-125a-5p and hsa-