ESTRO 37 Abstract book

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ESTRO 37

The clonogenic assays showed that the colony numbers for A375 cells with the 6-well IMRT plan for 0, 2, 4, 8, 16 and 24 Gy were 208, 141, 74, 0, 0, 0 and for the open- field homogeneous irradiations they were 194, 143, 55, 0, 0, 0. These differences did not reach statistical significance (p = .92, unpaired t-test) ( Figure 2, a & b ). The quantitative γ-H2AX analysis showed a radiation dose dependant increase in γ-H2AX signal intensity. Mean relative γ-H2AX signal intensity (normalised to the cell number) for 0, 2, 4, 8, 16 and 24 Gy with the 96-well IMRT plan were 4.74, 11.74, 18.68, 32.63, 60.51, 88.40 and the corresponding values for open-field, homogeneous irradiations were 7.15, 16.33, 23.83, 41.35, 64.3 and 102.7. These differences were not statistically significant (p = .75 unpaired t-test) ( Figure 2, c & d ).

effects. For this reason, most of the studies investigating the radiosensitizer effects of high atomic number (Z) NPs had used kilovoltage (keV) energies to get the advantage of PE effect which is directly propotional to almost Z 4 -Z 4.6 The purpose of this study was to assess SPION’s in vitro radiosensitizer effect at clinically utilized 6MV energies which remains relatively as an unexplored issue and to calculate Nanoparticle Enhancement Ratio (NER) of SPIONs. Material and Methods Citrate coated- SPION’s were synthesized and characterized by TEM . The size distribution of nanoparticles was determined by dynamic light scattering. Trypan blue and metabolic activity tests were performed to test the toxicity. MCF-7, MDAMB-231 and MDAH-2774 cell lines were used. Cell cultures were irradiated at 0,2,4,6, and 8Gy at 6MV energy level. Clonogenic survival assays were carried out. NER values were calculated based on clonogenic assays for each single radiation dose. Results SPIONs were biocompatible. NER values were cell line specific and dose dependent. The highest radiosensitization effects were seen in radiosensitive MCF-7 and MDAH 2447 cells at 2Gy (NER: 1.49 and 1.39 respectively), in relatively radioresistant MDA-MB-231 cells at 4Gy (NER:1.20).By increasing doses radiosenisitizer effect disappeared; at 6Gy there was minimum radiosensitization effect only in MCF-7 cells (NER:1.10), at 8Gy there wasn’t any radiosensitization in any cell line (NER:1.03-1.08). Table1. MCF-7: Human breast adenocarcinoma, MDAH- 2774: human ovarian carcinoma, MDAMB-231: human breast adenocarcinoma Cell line 0Gy 2Gy 4Gy 6Gy 8Gy MCF-7 1.00 1.49 1.32 1.12 1.05 Conclusion Maximal NER value (1.49) which was displayed on MCF-7 cell lines at 2Gy, which is a dose fractionation widely used in clinical practice means; with same biological effect on tumor cells and less side effects on normal tissue, 1.3Gy can replace 2Gy in presence of SPIONs, which might fulfill major requirement in radiotherapy to widen therapeutic window. Our results raise the possibility that by synergistic effect, SPIONs may cause dose dependent and cell line spesific radiosensitization at 6MV X-ray energies. EP-2314 Novel RG108-derived DNA-methyltransferase inhibitor as a radiosensitizer in glioblastoma cells C.W. Wee 1 , J.H. Kim 1 , H.J. Kim 1 , S.Y. Suh 1 , H.C. Kang 1 , B.S. Shin 2 , E. Ma 3 , I.H. Kim 1 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of 2 Sungkyunkwan University, School of Pharmacy, Suwon-si, Korea Republic of 3 Catholic University of Daegu, College of Pharmacy, Gyeongsan-si, Korea Republic of Purpose or Objective The prognosis of glioblastoma (GBM) is dismal despite radiotherapy and temozolomide, and therefore, novel radiosensitizers to enhance the therapeutic ratio are MDAH-2774 1.00 1.39 1.13 1.05 1.08 MDA-MB-231 1.00 1.15 1.20 1.01 1.03

Conclusion We have validated a high-throughput, in-vitro radiobiology platform by comparing three relevant and important biological parameters to conventional open- field irradiations. This platform is now in routine use for radiobiology experiments within our Institute. References 1 A high-throughput in-vitro platform for radiobiology experiments; National Cancer Research Institute Cancer Conference, November 2017, Liverpool, UK, Abstract ID: 849 EP-2313 Magnetic nanoparticle mediated in-vitro radiosensitization at megavoltage radiation energies E. Korkmaz Kıraklı 1 , G. Takan 2 , S. Hoca 3 , F.Z. Biber Müftüler 2 , A. Yurt Kılçar 2 , S. Arun Kamer 3 1 Dr. Suat Seren Chest Diseases and Surgery Research and Educational Hospital, Radiation Oncology, İzmir, Turkey 2 Ege University Institute of Nuclear Sciences, Department of Nuclear Applications, izmir, Turkey 3 Ege University, Departement of Radiation Oncology, Izmir, Turkey Purpose or Objective Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are the member of magnetic nanoparticle (NP) family. SPIONs, in combination with radiotherapy have been representing themselves as novel radiosensitizers in recent years.NPs’ small size relative to other radiosensitizers, give them the advantage of increased permeation, internalization and evading the host’s immune system.SPIONs have many favorable features including; cheapness, ease of synthesis, biocompatibility, reproducibility in wide range of diameters, applicability to be coated with variety of surface coatings, ability of tumor specific cytotoxic heating when excited by external alternating magnetic field. Cell damaging effects as a consequence of interaction between high Z NPs and low energy X-rays caused mainly by photoelectric