ESTRO 36 Abstract Book

S87 ESTRO 36 _______________________________________________________________________________________________

tumour model under realistic, i.e. harsh, conditions at experimental laser accelerators. Results: Both human tumour models showed a high take rate and continuous tumour growth after reaching a volume of ~5 – 10 cubic millimetres. Moreover, immunofluorescence analysis revealed that already the small tumours interact with the surrounding tissue and activate endothelial cells to form vessels. By analysing the dose dependent tumour growth curves after 200 kV X-ray treatment a realistic dose range, i.e. for inducing tumour growth delay but not tumour control, was defined for both tumour entities under investigation. Beside this basic characterization, the comparison of the influence of laser- driven and conventional (clinical Linac) electron beams on the growth of FaDu tumours reveal no significant difference in the radiation induced tumour growth delay. Conclusion: The mouse ear tumour model was successfully established and optimized providing stable tumour growth with high take rate for two tumour entities (HNSCC, glioblastoma) which are of interest for patient treatment with protons. Experiments comparing laser-driven and conventional proton beams in vivo as the next step towards clinical application of laser-driven particle acceleration are under way. Acknowledgement: The work was supported by the German Government, Federal Ministry of Education and Research, grant nos. 03ZIK445 and 03Z1N511. SP-0170 Novel models in particle biology research P. Van Luijk 1 1 van Luijk Peter, Department of Radiation Oncology, Groningen, The Netherlands The unique behaviour of particles that causes them to reach maximum dose deposition at the end of their track makes them useful for facilitating both treatment intensification and reduction of normal tissue damage. On a macroscopic scale particles facilitate reducing normal tissue dose and irradiated volume. Though it has been known for a long time that reducing the amount of irradiated normal tissue reduces toxicity, the increased precision of particles also makes sparing of substructures possible and offers more flexibility in choosing how to distribute inevitable excess dose over the normal tissues. However, it is also these unique properties that limit the information in available clinical data that can be used to guide optimal use of particles. Filling this gap is an important topic of particle radiobiology that has been approached with various in vivo models. On a microscopic scale particles deposit dose with a higher ionization density, especially near the end of the particle track, usually positioned in the target volume. Increased ionization density has been demonstrated to change response, both in terms of severity and potentially even in type. These effects have been studied mostly in 2D in vitro models. However, even though in 2D cell cultures differential effects between high- and low-LET radiation are observed, these models seem to be more radiosensitive than one would expect based on clinical data. Interestingly it has been observed that cells respond markedly different when irradiated in a more tissue- equivalent 3D culture system. Moreover, recent insights from stem cell biology indicate a potentially critical role of stem cells both in tumour and normal tissue response. Taken together, 3D culture systems based on tissue-specific stem cells may offer new opportunities to better understand the response of tumours and normal tissues to particle irradiation.

SP-0169 A small animal tumour model for low-energy laser-accelerated particles J. Pawelke 1,2 , K. Brüchner 3,4 , M. Krause 4,5,6 , E. Leßmann 2 , M. Schmidt 5 , E. Beyreuther 2 1 OncoRay - National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus-Technische Universität Dresden, Department of Medical Physics- Laser Radiooncology Group, Dresden, Germany 2 Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiation Physics, Dresden, Germany 3 Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden, Experimental Center, Dresden, Germany 4 Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology, Dresden, Germany 5 OncoRay - National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus-Technische Universität Dresden, Department of Radiation Oncology, Dresden, Germany 6 German Consortium for Translational Cancer Research DKTK and German Cancer Research Center DKFZ, Dresden Site, Dresden, Germany Introduction: The long-term aim of decveloping laser- based acceleration of protons and heavier ions towards clinical radiation therapy application requires not only substantial technological progress, but also the radiobiological characterization of the resulting ultra- short and ultra-intensive particle beam pulses. Recent in vitro data showed similar effects of laser-accelerated versus conventional proton beams on clonogenic cell survival and DNA double-strand breaks. As the proton energies currently achieved for radiobiological experiments by laser-driven acceleration are too low to penetrate standard tumour models on mouse legs, a small animal tumour model allowing for the penetration of low energy protons (~20 MeV) was developed to further verify the effects in vivo. Methods: The mouse ear tumour model was established for human HNSCC FaDu and human glioblastoma LN229 cells. For this, cells were injected subcutaneously in the right ear of NMRI nude mice and the growing tumours were characterized with respect to growth parameters and histology. After optimizing the number of injected cells and used medium (PBS, Matrigel) the radiation response was studied by 200 kV X-ray irradiation. Furthermore, a proof-of-principle full scale experiment with laser- accelerated electrons was performed to validate the FaDu

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