Abstract Book

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reaction, as also seen by the OCT angiography maps ( Fig.1c,e,g ); after start of anti-mucositis therapy the microvascular increase tended to slow down ( Fig.1g,h ). These visual conclusions were confirmed by quantitative processing of the OCT images. Statistically significant changes of microvascular parameters were detected when grade one, two and three mucositis developed ( Fig.1i ). In addition to these general trends based on the analysis of all examined patients, the real potential of OCT microvascular monitoring was evident in patients who received IMRT. OCT metric corresponded to different dose accumulated in the PTV, dependent on tumor location and treatment modality. Conclusion The study showed that OCT angiographic monitoring can be used for objective evaluation of radiation induced microvascular changes, thus ‘shedding light’ on early functional and structural radiation toxicity. This may potentially play a role in the design and efficacy evaluation of treatment and prophylaxis modalities of mucositis and in the implementation of adaptive radiotherapy protocols. PO-1045 Photon, proton and C12 irradiation influences maturation and functionality of dendritic cells L. König 1 , A. Hommertgen 1 , D. Bernhardt 1 , J. Hörner- Rieber 1 , P. Huber 1 , K. Herfarth 1 , J. Debus 1 , S. Rieken 1 1 University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg, Germany Purpose or Objective Radiotherapy (RT) induces DNA-damage that either causes induction of tumor cell death or inhibition of the proliferating capacity of these cells. Furthermore, considerable evidence emerges that antineoplastic effects extend beyond these mechanisms. Those secondary effects contribute to anti-tumor responses in a local but also systemic manner via activation of the immune system: The role of dendritic cells (DCs) is well described to be essential for priming effective radiation- induced adaptive immunity. Through increased release of tumor-associated antigens (TAA) after RT, DCs are recruited and cross-presentation of TAA leads to activation of B- and T-lymphocytes, therefore playing a pivotal role in adaptive immune response and immunogenic cell death. However, there are still many hypotheses regarding the influence of RT on activation of the immune system. The aim of our experiments is to further characterize the impact of different radiation types and dosages on differentiation and functionality of DCs. Material and Methods Human CD14-positive monocytes were isolated from peripheral blood mononuclear cell samples. After cytokine stimulation with Interleukin-4 (IL-4) and granulocyte macrophage colony-stimulating factor (GM- CSF) monocytes were induced into immature DCs (iDCs) and later mature DCs (mDCs). Monocytes were irradiated with different radiation doses (1x15Gy, 5x2Gy, 1x0.5Gy) and radiation types (photons, protons, carbon ions) on day 0. Maturation to mDCs was induced on day 7 by adding tumor necrosis factor alpha (TNFα) to the culture Poster: Radiobiology track: Radiobiology of proton and heavy ions

medium. Differentiation and maturation of DCs was assessed by staining of cell surface molecules CD14, CD83, CD80, CD86, CD209 und HLA-DR via flow cytometry. Functional analysis of irradiated DCs was performed through FITC-labelled phagocytosis assay, migrational assays and IL-12 ELISA. Results No major significant changes in the immune profile during differentiation of monocytes (CD14 + , CD83 - , CD86 + , CD80 - , HLA-DR + ) into iDCs (CD83 - , CD86 - , CD80 - , HLA-DR + ) and mDCs (CD83 + , CD86 + , CD80 + , HLA-DR ++ ) were seen after treatment with different radiation doses and types compared to the untreated control group. Functional analysis showed no difference in the phagocytotic and IL- 12 secretion capacity of irradiated iDCs and mDCs compared to the control group, whereas migrational capacity was induced after proton irradiation, compared to the other irradiation types. Conclusion Our experiments reveal that after irradiation with different doses and types maturation of DCs was unchanged compared to the control group. The capability for phagocytosis was unaffected after irradiation of DCs, indicating persistent functionality of the immune system. An additional RT-induced effect of particle therapy on the immunogenic potential of DCs is possible due an increase of IL-12 secretion and migrational capacity and will be investigated further. PO-1046 Dose-dependent changes after proton and photon irradiation in zebrafish model S. Brunner 1 , T. Tokes 1 , R. Szabo 1 , Z. Szabo 1 , R. Polanek 1 , E. Beyreuther 2 , J. Pawelke 3 , K. Hideghety 4 1 ELI-ALPS- ELI-HU Non-Profit Ltd, Szeged, Hungary 2 Helmholtz-Zentrum Dresden- 3OncoRay– National Center for Radiation Research in Oncology Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität, Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Uni, 3 Helmholtz-Zentrum Dresden- 3OncoRay – National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden, Faculty of Medicine and University Hospital Carl Gustav Carus- Tech, 4 ELI-ALPS- ELI-HU Non-Profit Ltd, Department of Oncotherapy- Szeged- Hungary-, Szeged, Hungary Purpose or Objective The laser-driven ionizing (LDI) beams have unique property of ultra-high dose rate, ultra-short pulses and carry the potential toward special clinical application. Our aim was to establish an in vivo zebrafish model for radiobiological research on later LDI radiation. Material and Methods 24 hours post-fertilization (hpf) zebrafish (Danio rerio) embryos were irradiated at OncoRay Institution, Dresden with escalated doses (5, 10, 15, 20 and 30 Gy) at two positions along the proton depth-dose curve (PDDC): at the plateau and at the middle of Spread Out Bragg Peak (mSOBP), furthermore, with reference conventional photon beam (n=96 in each group). The experiment were 3 times repeated, under the same conditions. On the 3 th (96 hpf) and 4 th (120 hpf) days after irradiation morphological malformations were documented (photo) and determined quantitatively. Two independent observers measured the length of the embryos, the degree of the yolk sac edema and the diameter of the eyes. Additionally, we have detected the DNA double- strand breaks immunohistochemically (gamma-H2AX)