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multivariate analysis, elevated pCaspase 8 and Plk3 expression correlated with better outcome. Furthermore, elevated peripheral WBC count predicted for worse distant-metastasis-free survival, DFS and OS and also correlated with a lower intratumoral CD8 expression. Additionally, high TAN expression in the peritumoral compartment was associated with a significantly lower density of CD8, albeit TAN expression lacked prognostic value. Conclusion The present data provide, for the first time, mechanistic insight for the better response to chemoradiotherapy and favorable clinical outcome of HPV16-positive patients, and the worse prognosis in patients with pretreatment peripheral blood leukocytosis. Our findings are highly relevant for future treatment stratification with PD-1/PD- L1 immune checkpoint inhibitors to complement chemoradiotherapy and should be explored in a clinical trial. OC-0151 Potential predictive biomarkers of chemoradiation response in rectal cancer: a metabolomic study C. Rosa 1 , F. Perrotti 1 , L. Caravatta 1 , M. Di Tommaso 1 , D. Pieragostino 2 , I. Cicalini 2 , C. Rossi 2 , M.C. Cufaro 2 , D. Genovesi 1 1 SS. Annunziata Hospital- “G. D’Annunzio” University, Department of Radiation Oncology, Chieti, Italy 2 “G. D’Annunzio” University, Analytical Biochemistry and Proteomics Laboratory- Research Centre on Aging and Translational Medicine Ce.S.I-MeT, Chieti, Italy Purpose or Objective The ability to predict tumor response before neoadjuvant treatment, in locally advanced rectal cancer (LARC) patients, could significantly improve personalized treatments. A promising biomarker discovery platform is represented by blood and urinary metabolomics, with their minimally invasive characteristic and their easily accessible obtainings. Aim of this study is to investigate a metabolomic approach for highlighting aminoacid and acylcarnitine, misured as indirect markers of fatty acid and protein catabolism, able to predict tumor response. Material and Methods Between March 2013 and September 2014, 18 patients (11 men and 7 women), affected by LARC, were treated with neoadjuvant CRT. Sera were collected during routine chemistry tests before treatment (T0), at day 14 (T14) and at day 28 (T28) of CRT. Different aminoacid, acylcarnitine and ceramides were validated by an independent approach and studied during treatment. Correlations were performed according to Mandard classification. Results At T0 6 of 21 aminoacids analysed significantly differentiated responder (RP) to no-responder (NRP) patient: leucine/isoleucine/OH-proline, methionine, tyrosine and histidine. At T14 those aminoacids did not maintain their significance, whereas others, represented by proline, valine and alanine, became significantly differentiated between RP and NRP. At T28 only valine continued to remain different with a significance. Considering acylcarnitine, only free acylcarnitine significantly differentiated RP to NRP (T28) (Figure1). Regarding ceramides the analysis resulted ongoing.

Conclusion A personalizing treatment strategy is necessary to improve survival outcomes in rectal cancer patients. Metabolomics could be considered as a hopeful opportunity to provide a better molecular definition of LARC. In our pilot study we highlighted one acylcarnitine and six aminoacids able to predict, before CRT, treatment response, differentiating RP to NRP, thanks to a modulation of serum metabolites during CRT. Our preliminary results will be validated in an ongoing independent cohort of LARC patients. OC-0152 Glutamine metabolism as potential biomarker and target for prostate cancer radiosensitization A. Dubrovska 1 , A. Tyutyunnykova 2 , O. Chen 2 , A. Linge 3 , S. Löck 2 , V. Telychko 2 , S. Richter 4 , L. Hein 2 , M. Toma 5 , S. Zschaeck 6 , G. Eisenhofer 4 , M. Wirth 7 , L. Kunz-Schughart 2 , B. Tawk 8 , C. Schwager 8 , A. Abdollahi 9 , G. Baretton 10 , M. Krause 11 , M. Baumann 12 1 OncoRay - National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden and Helmholtz-Zentrum Dresden-Rossendorf- Institute of Radiooncology – OncoRay- Dresden- Germany, , 2 OncoRay - National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden and Helmholtz-Zentrum Dresden-Rossendorf- Institute of Radiooncology – OncoRay- Dresden- Germany, , 3 OncoRay - National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden and Helmholtz-Zentrum Dresden-Rossendorf- Institute of Radiooncology – OncoRay- Dresden- Germany, , 4 Department of Clinical Chemistry and Laboratory Medicine- University Hospital Carl Gustav Carus- Technische Universität Dresden- Dresden- Germany, Dresden, Germany 5 Department of Pathology- University Hospital Bonn, Bonn, Germany 6 Department of Radiation Oncology- University Hospital Carl Gustav Carus- Technische Universität Dresden- Dresden- Germany, Dresden, Germany 7 Department of Urology- University Hospital Carl Gustav Carus- Technische Universität Dresden- Dresden- Germany, Dresden, Germany 8 German Cancer Consortium DKTK- DKFZ Heidelberg- Germany- National Center for Tumor Diseases NCT- Heidelberg Ion Therapy Center HIT, Heidelberg, Germany 9 German Cancer Consortium DKTK- DKFZ Heidelberg- Germany- National Center for Tumor Diseases NCT- Heidelberg Ion Therapy Center HIT- Heidelberg Institute of Radiation Oncology HIRO, Heidelberg, Germany 10 German Cancer Consortium DKTK- Department of Pathology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden- Dresden- Germany, Dresden, Germany 11 OncoRay - National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden and