Abstract Book

S1267

ESTRO 37

Material and Methods The present study was designed to establish a panel of patient-derived HNSCC cell lines with individual subclones and to subject them to molecular characterization and functional analyses of radiosensitivity. Short tandem repeat (STR) typing was used for identification in comparison to previously preserved tumor material. Several markers, including pan-Cytokeratin, EpCAM, EGFR and fibroblast-specific protein were examined by immunofluorescence and flow cytometry. Clonogenic survival upon irradiation with single doses of 0-8 Gy and a fractionated regimen of 1 to 4x 2 Gy was analyzed. Molecular characterization was started with array comparative genomic hybridization (aCGH) assays in order to analyze DNA copy number changes. Results The established primary cell cultures of so far 2 patients and their individual subclones (5 each) showed unique STR profiles and exhibit long-term proliferation capacity. Thus, they can be considered as novel and immortalized cell lines. We observed clear inter- and intra-individual differences in epithelial marker expression and in clonogenic survival upon different irradiation regimens suggesting that HNSCC inter- and intra-tumoral heterogeneity can be reflected by these cell culture models – at least to a certain extent. We found profound differences in aCGH profiles between the cell lines from different patients. Furthermore, we saw clear changes in DNA copy number alterations between intra-individual To our knowledge, the present cell line panel is a so far unique platform to analyze tumor heterogeneity of HNSCC. We suggest that differences in the radiation response can be reflected by molecular data of several levels. To this end, we will continue the molecular characterization of the established cell lines on the methylome, mRNAome, and miRNAome level and will include more patients. Correlation analyses of functional data of the radiation response with molecular data will help to identify pathways and/or networks that are essentially involved in therapy resistance. EP-2296 Effect of radiochemotherapy on T2* MRI signal in HNSCC and its relation to FMISO-PET derived hypoxia N. Wiedenmann 1 , H. Bunea 1 , H. Rischke 1,2 , A. Bunea 1 , L. Majerus 1 , L. Bielak 3 , A. Protopopov 3 , U. Ludwig 3 , M. Büchert 3 , C. Stoykow 2 , M. Mix 2 , P. Meyer 2 , M. Bock 3 , A. Grosu 1,4,5 1 University Medical Center Freiburg, Department of Radiation Oncology, Freiburg, Germany 2 University Medical Center Freiburg, Department of Nuclear Medicine, Freiburg, Germany 3 University Medical Center Freiburg, Department of Radiology - Medical Physics, Freiburg, Germany 4 German Cancer Research Center, DKFZ, Heidelberg, Germany 5 German Cancer Consortium DKTK, Partner Site Freiburg, Freiburg, Germany Purpose or Objective Current noninvasive methods to assess tumor hypoxia include 18 F-misonidazole PET (FMISO-PET) and novel MRI techniques. Measurement of transverse relaxation time (T2*) has been proposed as a marker of tumor oxygenation. Purpose of the current study was to assess the effect of radiochemotherapy (RCT) on T2* signal in subclones. Conclusion

HNSCC at an early (week 2) and late (week 5) time point during treatment and to analyse the relation between T2* and the hypoxic tumor subvolume assessed by 18 F- misonidazole PET. Material and Methods Patients underwent 18 F-FDG PET/CT at baseline and serial 18 F-FMISO PET/CT imaging and serial 3 Tesla MRI imaging for contrast enhanced T1 (T1 Gd), T2, T2* in weeks 0, 2 and 5. Image data was coregistered on the treatment planning system (iplan, BrainLAB). Gross tumor volumes for tumor and lymphnode metastasis (GTV-T, GTV-LN) and normal tissue (NT) were contoured on contrast enhanced MRI T1. Hypoxic tumor subvolumes (HSV-T), hypoxic lymph node subvolumes (HSV-LN), and complementary non-hypoxic tumor subvolumes and non- hypoxic lymph node subvolumes (nonHSV-T, nonHSV-LN) were generated for a threshold level of 1.4 times the mean NT SUV FMISO. For T2* MRI and FDG analysis, mean values were obtained within GTV-T, GTV-LN, HSV-T, HSV- LN, nonHSV-T, nonHSV-LN, and NT. SPSS was used for statistical analysis (paired t-tests). Results 10 patients met inclusion criteria for image analysis by presenting a complete set of serial FMISO PET data and serial 3T MRI data. GTV-T and GTV-LN decreased from week 0 to 5 by -56%+/-16.1 and -63 %+/-23.4. HSV-T and HSV-LN nearly completely resolved from week 0 to 5 by - 99.99%+/-0.02 and by -96.43%+/-9.45. Mean T2* signal showed no significant change over time for GTV-T (week 0 to 2, 5: 19.1+/-3.1, 19.1+/-3.6, 20.8 +/-3.9) while for GTV-LN a slight decrease week 2 to 5 was seen (26.8+/- 7.1, 27.6+/-6.8, 22.6+/-4.2: p≥0.05). For GTV-LN higher T2*values were found than for GTV-T for all time points (week 2: p=0.009). Within HSV-T mean T2* values were smaller compared to nonHSV-T for all timepoints, reaching borderline significance level at week 0 (15.0+/- 4.6) for HSV-T versus 18.3+/-2.9 for nonHSV-T, p=0.051). FDG SUVmean was significantly higher within hypoxic regions of both tumor and lymphnodes: HSV-T 12.1+/-5.5 as compared to nonHSV-T 6.1+/-2.6 and HSV-LN of 10.2+/-3.9 as compared to nonHSV-LN of 4.7+/-1.9, p≤0.026 and p≤0.008. Conclusion On MRI tumor reduction and on FMISO-PET marked reduction of tumor hypoxia (reoxygenation) was found in- line with previous findings. No significant T2*change was found within the tumor and the lymphnodes over time. For the hypoxic tumor subvolume significantly smaller T2* values were found as compared to the non-hypoxic tumor subvolume, indicating a correlation between oxygenation status and T2* signal. Significantly larger FDG SUVmean values were found within the hypoxic tumor subvolume as compared to the non-hypoxic tumor subvolume. EP-2297 Biodosimetry of head and neck cancer patients undergoing radiation therapy R. Kulshrestha 1 , A.K. Rathi 1 , S. Kapoor 2 , K. Singh 3 , S. Arora 3 , S.K. Polipalli 4 , A. Jindal 2 1 Maulana Azad Medical College, radiation oncology, Delhi, India 2 Maulana azad medical college, Paediatrics, New Delhi, India 3 Maulana azad medical college, Radiation oncology, New Delhi, India 4 Maulana azad medical college, Cyto genetics, New Delhi, India

Purpose or Objective