ESTRO 2020 Abstract Book

S169 ESTRO 2020

Center of Pathology NCP, Dudelange, Luxembourg ; 10 Luxembourg Institute of Health LIH, Luxembourg Center of Neuropathology LCNP, Luxembourg, Luxembourg ; 11 Luxembourg Institute of Health LIH, Department of Oncology, Luxembourg, Luxembourg ; 12 University of Luxembourg, Luxembourg Centre for Systems Biomedicine LCSB, Esch-sur-Alzette, Luxembourg ; 13 University Hospital Düsseldorf UKD- Heinrich Heine University, Department of Radiotherapy and Radiation Oncology, Düsseldorf, Germany ; 14 University Hospital Düsseldorf UKD- Heinrich Heine University, Department of Neurosurgery, Düsseldorf, Germany ; 15 University Hospital Frankfurt, Department of Radiation Oncology, Frankfurt, Germany ; 16 University Hospital- LMU Munich, Department of Neurosurgery, Munich, Germany Purpose or Objective With a median overall survival (OS) of approx. 14-16 months the prognosis of patients with glioblastoma remains dismal. In a previous study we identified a 4- miRNA signature as prognostic factor for OS in glioblastoma patients who were treated according to the EORTC 26981/22981-NCIC CE3 trial. The signature was independent of known prognostic factors including the MGMT promoter methylation status. In the present study, we validated the signature and assessed the prognostic relevance of the combination of the 4-miRNA signature with MGMT promoter methylation status. Material and Methods The validation cohort (n=106) contained IDH1/2 wildtype tumors with respective treatment and known MGMT promoter methylation status with patients from the LMU Munich (n=37), the University Hospital Düsseldorf (n=33) and The Cancer Genome Atlas (TCGA, n=36). Risk scores were calculated using signature expressions in combination with the signature Cox model coefficients. The combination of miRNA signature with MGMT -promoter methylation defined four risk groups which were used for univariable/multivariable analysis for OS. C-index was used to determine prognostic performance. Results The 4-miRNA signature was independent of sex, age and MGMT promoter methylation status (p> 0.05). 4-miRNA signature-defined high-risk (n=48, med. OS: 16.8 months) and low-risk (n=58, med. OS: 28.8 months) patients (HR: 2.21, 95%-CI: 1.33-3.69, p=0.0018). 56 patients with methylated MGMT promoter had superior OS (med. OS: 26.4 months) compared to the non-methylated group (med. OS: 16.8 months, p=0.0036, HR: 0.45, 95%-CI: 0.26- 0.78). The four groups resulting from combining miRNA risk signature and MGMT promoter methylation status were associated with OS (p=0.0004): patients with the signature low-risk/ MGMT promoter methylated had a median OS of 37.2 months, the signature low-risk/ MGMT non-methylated and signature high-risk/ MGMT methylated had median OS of 18 and 25.2 months, respectively. The signature high- risk/ MGMT non-methylated group had a median OS of 14.4 months. Compared to the models including the signature and MGMT promoter methylation alone, the C-indices resulting from the Cox model combining the signature and MGMT promoter methylation showed superior prediction performance over the whole observation time. Conclusion We confirmed the 4-miRNA signature as an independent prognostic marker in patients with IDH-wildtype glioblastoma. Survival prediction by combining with MGMT promoter methylation outperformed other established prognostic factors. Yet, and comparable to the

Single cells of three primary cultures from locally advanced HNSCC were profiled by single-cell RNA sequencing. Results While HNSCC-specific alterations were identified, the mutational and genomic copy number patterns of primary and recurrent tumors were mostly discordant and showed only a low relationship between pairs of primary and relapsed tumors. This heterogeneity between tumor pairs was also reflected by the transcriptional distance. Transcriptional subtypes according to Keck et al. (2015) comprising classical (CL), basal (BA) and inflamed- mesenchymal (IM) subtypes were assigned to all tumor samples. 15 out of the 34 tumor pairs exhibited a change in transcriptional subtype between primary and recurrent tumor and eight of these subtype switchers changed the molecular subtype from IM to either CL or BA. To explore the clinical impact of subtype changes between tumor pairs, all samples were investigated for established prognosis parameters (hypoxia, radiation resistance, pEMT, survival-score) and the expression of representative gene signatures in primary/relapsed tumors. Change of transcriptional subtypes between tumor pairs was associated with significantly improved outcome (‘locoregional relapse/recurrence’; p-value=0.0238, HR=0.43, 95%-CI=0.21-0.91). PD-L1 expression was frequently different between primary and relapsed tumors. Remarkably, the CL subtype showed almost no PD- L1 expression. This is also true for all relapsed tumors of the larger cohort with a CL subtype (p-value=0.0008). Single-cell RNA sequencing analysis of primary cultures revealed co-presence of different transcriptional subtypes in primary tumors suggesting a selection and enrichment of cells of a certain subtype in the course of radiochemotherapy. Conclusion Molecular heterogeneity was observed between matched primary and recurrent tumor tissues, which revealed the existence of transcriptional subtype switching within some patients. Our results point towards a selection of specific subtypes in relapses that exhibit unfavorable tumor properties and have possible effects on therapy innovations. This study suggests to tailor therapy also to the above mentioned specifics of the recurrent tumor. OC-0322 4-miRNA signature and MGMT promoter methylation improve risk stratification in glioblastoma. K. Unger 1,2,3 , D.F. Fleischmann 2,4,5 , V. Ruf 6 , J. Felsberg 7,8 , D. Piehlmaier 1 , D. Samaga 1 , J. Heß 1,2,3 , M. Mittelbronn 9,10,11,12 , K. Lauber 2,3,5 , W. Budach 13 , M. Sabel 14 , C. Rödel 15 , G. Reifenberger 7,8 , J. Herms 6 , J. Tonn 16 , H. Zitzelsberger 1,2,3 , C. Belka 2,3,5 , M. Niyazi 2,5 1 Helmholtz Zentrum Muenchen - German Research Center for Environmental Health, Research Unit Radiation Cytogenetics, Neuherberg, Germany ; 2 University Hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany ; 3 Helmholtz Zentrum München- German Research Center for Environmental Health GmbH, Clinical Cooperation Group “Personalized Radiotherapy in Head and Neck Cancer”, Neuherberg, Germany ; 4 DKFZ, German Cancer Research Center, Heidelberg, Germany ; 5 German Cancer Consortium DKTK, Partner Site Munich, Munich, Germany ; 6 LMU Munich, Center for Neuropathology and Prion Research, Munich, Germany ; 7 University Hospital Düsseldorf UKD- Heinrich Heine University, Institute for Neuropathology, Düsseldorf, Germany ; 8 German Cancer Consortium DKTK, Partner Site Essen/Düsseldorf, Essen/Düsseldorf, Germany ; 9 Laboratoire National de Santé LNS, National