ESTRO 38 Abstract book

S11 ESTRO 38

[4]https://www.ptb.de/emrp/bioquart.html [5] Rabus H et al. Biologically Weighted Quantities in Radiotherapy: an EMRP Joint Research Project . EPJ Web of Conferences 77: 00021 (2014). [6] Palmans H et al. Future development of biologically relevant dosimetry . Br. J. Radiol. 88: 20140392, (2015). [7]http://www.emrponline.eu/ [8] Conte V et al. Track structure characterization and its link to radiobiology , Radiat. Meas. 106, 506-511 (2017). [9] Patrono C et al. “BioQuaRT” Project: design of a novel in situ protocol for the simultaneous visualization of chromosomal aberrations and micronuclei after irradiation at microbeam facilities, Radiat. Prot. Dosim. 166, 197-199 (2015). [10] Villagrasa C et al., Geant4-DNA simulation of DNA damage caused by direct and indirect effects and comparison with biological data , EPJ Web of Conferences 153, 04019, 1-6 (2017). [11] Testa A et al. Analysis of radiation-induced chromosome aberrations on cell-by-cell basis after alpha- particle microbeam irradiation: experimental data and simulations , Radiat. Res. 189, 597-604 (2018). [12] Gonon G et al., From Energy Deposition of Ionizing Radiation to Cell Damage Signaling: Benchmarking Simulations by Measured Yields of Initial DNA Damage after Ion Beam Irradiation , under review at PloS Comp. Biol. [13] Rabus H et al. Investigation into the probability for miscounting in foci-based assays , Proc. MICROS 2017, accepted for publication in Radiat. Prot. Dosim. (2018). [14] IAEA, “Application of Biomarkers of Radiation Exposure in Radiological Clinical Practice“ Human Health Series, International Atomic Energy Agency, Vienna, in preparation. [15]http://www.reneb.net/ [16] Baek W Y et al. Metrology for Biological Radiation Effects - Status and Metrological and Research Needs , PTB Report Dos 60, ISBN 978-3-95606-419-7 (2018). [17] Rabus H et al. Proposal for a European Metrology Network on Biological Ionising Radiation Effects , Proc. EPR BioDose 2018, to appear in Radiat. Prot. Dosim. (2019). SP-0036 Understanding biological response B.S. Sørensen 1 1 Aarhus University Hospital, Exp. Clin. Oncology, Aarhus C, Denmark Abstract text There are a number of biological characteristics that have been shown to influence differences in response to radiation for both the tumor and the surrounding normal tissue. These characteristic includes intrinsic radiosensitivity, hypoxia, HPV status, number of cancer stem cells (CSCs), and repopulation between radiotherapy fraction. In the last 20 years, significant progresses in the knowledge of the biological factors influencing radiation response and the causative molecular basis, such as the DNA-damage response and repair mechanisms, signaling pathways and tumor microenvironmental factors, have been made, which both has impact for therapeutic possibilities and has also generated a large number of potential biomarkers. The issue of biological response becomes more complicated when considering particle radiation. Protons and high LET radiation have a higher relative biological effectiveness (RBE), but RBE is a complex quantity, depending on both biological and physical parameters. RBE is often established as measured by cell death, but emerging evidence also demonstrate an altered response in the surviving cells. This is both evident for high LET radiation and for proton radiation. This differential biological effect is not only relevant in the tumour, but also in the normal tissue. Current research in particle radiobiology is, in addition to the RBE, focusing on the

Fig. 1: The BioQuaRT multi-disciplinary approach.

Apart from findings like a simply correspondence between cellular biological endpoints and nanodosimetric parameters of track structure [8], BioQuaRT also came up with novel metrological approaches to radiobiological assays [9-13]. The increasing use of biological assays in radiology [14] and the long-term aim of biology-based treatment planning in radio-oncology require developing a metrological fundament for radiobiology. As the challenges involved require resources and skills beyond those presently available at Metrology Institutes, an initiative has been formed to establish a European Metrology Network (EMN) on Ionizing Radiation Effects within the European Association of National Metrology Institutes (EURAMET). Such an EMN would link to existing networks in biological dosimetry [15] and would follow a strategic agenda for which four main topics have been identified in stakeholder consultations [16-17]: First, research towards identifying which microdosimetric or nanodosimetric radiation quantities best correlate with radiobiological effectiveness and the development of detectors for their primary realization as well as for practical measurements in clinical practice (Fig. 2). Second, measurements supporting uncertainty assessment and validation of numerical tools, e.g. Monte Carlo track structure codes, used in radio-oncology research. Third, metrology supporting the improvement of radiobiological assays in terms of reliability, reproducibility, solid measurement uncertainty assessment and model-based data interpretation. Fourth, cross-cutting the three aforementioned lines, standardization of procedures and development of tangible as well as written standards.

Fig. 2: Draft roadmap of the first EMN topic.

[1] IAEA, Relative Biological Effectiveness in Ion Beam Therapy , Technical Reports Series No. 461, International Atomic Energy Agency, Vienna 2008. [2] Hill M. The variation in biological effectiveness of x- rays and gamma rays with energy , Radiat. Prot. Dosim. 112, 471–481 (2004). [3] Nikjoo H. and Lindborg L. RBE of low energy electrons and photons , Phys. Med. Biol. 55, R65 (2010).