Abstract Book

S1263

ESTRO 37

Meanwhile, recurrent patients tended to exhibit increased post-RT peripheral neutrophil count (4.2×10 9 /L vs. 3.6×10 9 /L, p=0.09) and NLR (8.5 vs. 6.5, p=0.08) in comparison with non-recurrent patients. Multivariate analysis (MVA) identified patient age >50 years old (HR=3.4, p=0.02), weight loss during RT> 7.5% (HR=3.2, p=0.03), and post-RT peripheral NLR >7.05 (HR=2.5, p=0.04, 5-year OS 71.4% vs. 87.8%) as unfavorable prognostic factors for OS. There was also a non- significant trend in the MVA that patients with post-RT peripheral NLR >7.05 showed worse PFS (HR=1.9, p=0.06, 5-year PFS 64.1% vs. 81.8%). Conclusion Post-RT NLR predicted OS and PFS in LANPC patients treated with sequential chemoradiotherapy. The dynamic change of the routinely tested immune factors could help make appropriate treatment options and follow-up strategies. A. Gonnelli 1 , F. Pasqualetti 1 , M. Cantarella 1 , A. Molinari 1 , S. Montrone 1 , G. Restante 2 , E. Rofi 2 , D. Delishaj 1 , M. Del Re 2 , F. Paiar 1 1 University Hospital of Pisa, Department of Radiation Oncology, Pisa, Italy 2 University Hospital of Pisa, Department of Clinical Pharmacology, Pisa, Italy Purpose or Objective Glioblastomas (GBMs) are usually classified on the basis of clinical presentation in two entities with different prognosis, primary or secondary. The most important genetic signature of primary glioblastoma is the lack of IDH1 mutation, which is associated with a short life expectancy. In the present study, through the analyses of circulating tumor DNA (ctDNA), we retrospectively assessed the role of IDH1 mutation in GBM patients IDH1 wild type (wt) assessed on tumor tissue at diagnosis. Material and Methods From February 2010 to January 2017 in thirty-one patients referred to the University Hospital of Pisa with diagnosis of GBM, IDH1 wt, the circulating tumor DNA (ctDNA) was analyzed. All patients had KPS greater than 65 and age >18 years; of them 22 patients underwent gross tumor resection and 9 subtotal resection were included in the present analysis. Twenty-six patients received radio-chemotherapy and 5 chemotherapy only. Three ml of plasma were collected at the first radiological evalutation after surgery; ctDNA was extracted using a QIAmp Circulating nucleic acid Kit (Qiagen, Valencia, CA) and analysed for IDH1 p.R132H mutation by digital droplet PCR (ddPCR, BioRad, Hercules, CA). Primary endpoint was Overall Survival (OS), measured from the diagnosis of GBM to last follow- up or patient exitus , stratified using IDH1 mutation detected on ctDNA. Results In May 2017, at data analysis, patient median age was 60.1 years (range 50-69). By analyzing ctDNA, 8 patients were carrier of the IDH1 p.R132H mutation whereas 23 were confirmed as IDH1 wt. Median OS recorded in the entire cohort was 40 months (95%CI 1.1-87.4). Stratifyng patients for survival as IDH1 wt vs IDH1 mutant on ctDNA, the OS was 23 vs not reached, respectively, showing a trend of significance of p=0.095 Conclusion Among patients with GBM IDH1 wt on tumor tissue, we found a subgroup of patients with IDH1 mutated on EP-2288 Role of circulating DNA in Glioblatoma IDH1 wild type patients suitable for radiotherapy

ctDNA. The presence of IDH1 mutation on ctDNA were associated with better prognosis and could be considered as a biomarker to be further investigated in a larger series. EP-2289 ABT-199 and cetuximab in combination with photon radiation in head and neck cancer stem cells. S. Espenel 1 , J.B. Guy 1 , A.S. Wozny 2 , A. Vallard 1 , S. Louati 2 , A. Lauret 2 , S. Simonet 2 , D. Ardail 2 , G. Alphonse 2 , C. Rancoule 1 , C. Rodriguez-Lafrasse 2 , N. Magné 1 1 Institut de Cancérologie de la Loire Lucien Neuwirth, Radiation Oncology, St Priest en Jarez, France 2 Laboratoire de Radiobiologie Cellulaire et Moléculaire Lyon Sud, Radiobiology, Oullins, France Purpose or Objective Cetuximab (Anti-EGFR antibody) concomitantly with radiotherapy is a validated scheme in locally advanced head and neck squamous cell carcinoma (HNSCC). It was demonstrated that a subpopulation of Cancer Stem Cells (CSCs) under-expressed EGFR. Conversely, anti-apoptotic Bcl-2 protein is overexpressed in CSCs. This expression implicates resistance to apoptosis and high invasion- migration abilities. The aim of the present study was to assess the efficacy of ABT-199 (Anti-Bcl-2 antibody) and cetuximab combination, with or without photon radiation on HNSCC cell lines. Material and Methods Spheroid model was used to approach the in vivo model. HNSCC chemo-and radio-resistant human cell lines (SQ20B and FaDu) were used. SQ20B corresponding stem cell subpopulation (SQ20B-CSCs) was obtained by double cell sorting. Red fluorescent cells transducted with lentivirus were used to determine the 3D-Spheroid growth. Cells were treated with ABT-199 10 µM +/- cetuximab 5nM +/- 4 Gy photon irradiation. The IncuCyte ZOOM® live cell imaging system was used to measure spheroid growth, through 3D-red fluorescence quantification. Phospho-AKT (Ser473), phospho-MEK1/2 (Ser217/221), Bcl-2 and Bcl-xL protein expression were studied at baseline and in response to treatments. Results 3D-Spheroid growth of SQ20B and CSCs appeared to have a radically different phenotypic aspect. If SQ20B parental proliferated in a limited spheroid, SQ20B-CSCs invaded the entire well (Figure 1) . Cetuximab strongly inhibited spheroid growth of SQ20B parental cell line when it had a small effect on SQ20B-CSCs. Conversely, ABT-199 had no effect on parental cell line, but significantly inhibited this property on CSCs. Cetuximab-ABT-199 combined treatment had a significant and synergistic inhibitory effect on SQ20B parental cell line and SQ20B-CSCs spheroid proliferation. 4 Gy photon irradiation with drugs decreased the tumor size of more than 90% compared with the control arm. These results were confirmed on FaDu cell line. EGFR was overexpressed in SQ20B, and under-expressed in SQ20B/CSCs. Bcl-2 was overexpressed in SQ20B/CSCs. The ABT-199 + Cetuximab combination significantly decreased both Phospho-AKT (Ser473) and phospho-MEK1/2 (Ser217/221) expression. 4 Gy photon irradiation synergized this combination .