Abstract Book

S119

ESTRO 37

evaluation of imaging requirements and methods for five workflow steps: a) simulation and planning, b) image guidance, c) treatment verification, d) treatment evaluation and adaptation, e) 4D imaging for moving targets is on-going work in each of the sub-working groups. In this contribution, the results of the survey will be summarized and the roadmap for the IGPT-WP will be presented. SP-0221 EPTN WP5: Treatment planning systems T. Lomax PSI, Switzerland SP-0222 EPTN WP6: Radiobiology B.S. Sørensen 1 1 Aarhus University Hospital, Exp. Clin. Oncology, Aarhus C, Denmark Abstract text Particle therapy (PT) as cancer treatment, using protons or heavier ions, can provide a more favourable dose distribution compared to x-rays. While the physical characteristics of particle radiation have been the aim of intense research, less focus has been on the actual biological responses particle irradiation gives rise to. One of the biggest challenges for the radiobiology is the RBE, with an increasing concern that the clinical proton RBE of 1.1 is an oversimplification, as RBE is a complex quantity, depending on both biological and physical parameters, such as dose, LET, cellular and tissue radiobiological characteristics, and the endpoints studied. Most of the available RBE data is in vitro data, with very limited in vivo data available, especially in late-reacting tissues which provide the main constraints and influence the quality of life endpoints in radiotherapy. There is a need for systematic, large-scale studies to thoroughly establish the biology of particle radiation in a number of different experimental models in order to refine biophysical mathematical models that can potentially be used to guide PT. The aim of the EPTN WP6 is to form a network of research and therapy facilities. This would aim to standardise the radiobiological experiments, obtain more accurate predictive parameters than in the past. Coordinated research is required in order to deliver the most suitable experimental data. Abstract not received

imaging to define tumors better and to monitor their response to therapy. Key to this is the development of highly complex treatment planning software which can produce radiation plans far surpassing human capabilities to optimize complex radiotherapy. Radiation research with animal models has not played a major role in developing current radiotherapy practice, but this may be changing rapidly now due to two new developments. On the one hand ever more sophisticated models for cancer (often orthotopic) and normal tissues have been developed recently. On the other hand, technically sophisticated research platforms are now available in nearly one hundred laboratories. These platforms combine unprecedented capabilities for precision irradiation with very small fields e.g. in an arc, with various forms of integrated onboard high resolutions imaging. These research platforms allow for the first time to perform irradiation studies at the mouse/rat level, which start to resemble the clinical standard of image- guided radiotherapy. An accurate treatment planning system for irradiating rodent models with very small beams of kilovolt photons is now available (SmART-ATP), which makes use of the onboard high-resolutions CT imager to acquire anatomical images, and of the onboard bioluminescent imager (BLI) for targeting of e.g. hypoxic regions in the tumors. Further recent technical developments are the introduction of non-coplanar beams, dual-energy CT imaging, motion-gated therapy, motion-dependent dose calculations, and recommendations on standardization of dosimetry, QA and imaging in these novel platforms (ESTRO-ACROP recommendations). In a recent study we used both the onboard CT imager and the BLI to quantify disease progression and therapy response of an implanted orthotopic glioblastoma multiforme tumor model. A strong correlation was observed between CT volume and BLI-integrated intensity. We conclude that BLI intensity can be used to monitor tumor growth but that the use of both contrast- enhanced CT and BLI provides complementary tumor growth information, which is particularly useful for modern small animal irradiation devices that make use of CT and BLI for treatment planning, targeting, and monitoring. The final aim is to identify those combined novel treatments that are the most promising for clinical translation, such as radiation-induced immune response. In this work, we will report on the progress of technology development and research in this new field.

On behalf of the coordinators of WP6

Symposium: Mouse Cancer Clinic: models and modalities for precision imaging and radiotherapy in small animal models

SP-0223 State of the art and future developments of small animal imaging and radiotherapy platforms F. Verhaegen 1 , S. Van Hoof 1 , L. Schyns 1 , S. Yahyanejad 2 , B. Van der Heyden 1 , A. Vaniqui 1 , P. Granton 1 , L. Dubois 2 , M. Vooijs 2 1 Maastricht Radiation Oncology MAASTRO, Radiotherapy, Maastricht, The Netherlands 2 Maastricht Radiation Oncology MAASTRO, Radiobiology, Maastricht, The Netherlands Abstract text Advances in radiotherapy outcome for cancer treatment has mostly not been obtained from an improved fundamental insight in radiation response of normal and cancer tissues. The majority of advances stem from improved forms of high-precision beam delivery, and

SP-0224 Interrogating open issues in cancer precision medicine with patient-derived xenografts A. Byrne 1 1 Royal College of Surgeons in Ireland, Physiology and Medical Physics, Dublin, Ireland Abstract text Patient-derived xenografts (PDXs) have emerged as an important platform to elucidate new treatments and biomarkers in oncology. PDX models are used to address clinically relevant questions, including the contribution of tumour heterogeneity to therapeutic responsiveness, the patterns of cancer evolutionary dynamics during tumour progression and under drug pressure, and the mechanisms of resistance to treatment. The ability of PDX models to