ESTRO 36 Abstract Book

S299 ESTRO 36 _______________________________________________________________________________________________

clinical outcome. The majority of the implicated miRNAs were found to be involved in angiogenic processes, and in particular the PI3K-Akt signalling pathway. The first part of the lecture will focus on challenges and recent recommendations for isolation and characterisation of exosomes and their cargo in preclinical models and human biofluids, while the second part will present the latest developments within exosome research relevant to radiation oncology. 1. Andaloussi, et al. Nature Rev Drug Discov 2013;12:347– 357. 2. Muralidharan-Chari et al. J Cell Sci 2010;123:1603– 1611. 3. Mitchell et al. Proc Natl Acad Sci 2008;105:10513– 10518. 4. King KW et al. BMC Cancer 2012;12:421. 5. Park et al. Mol Cell Proteomics 2010;9:1085–1099.

mandating dosimetry based treatments and verification for molecular radiotherapy as well as for external beam radiotherapy, are due to be enacted in February 2018. The EANM has a task force specifically addressing this issue and have recently conducted the first European survey of MRT. This has found a wide discrepancy in practice. As the treatment of cancer with radiotherapeutics is acknowledged to be a form of radiotherapy, many scientific, logistical and political challenges must be addressed. This field epitomises the need for a multidisciplinary approach to improve clinical practice for the benefit of the patient.

Teaching Lecture: Basics, implementations, applications and limitations of Monte Carlo dose calculation algorithms

6. Li et al. Cancer Res 2016;76(7):1770–1780. 7. Kucharzewska et al. Proc Natl Acad Sci 2013;110(18):7312–7317.

SP-0559 Basics, implementations, applications and limitations of Monte Carlo dose calculation algorithms F. Verhaegen 1 1 Maastricht Radiation Oncology MAASTRO GROW - School for Oncology and Developmental Biology- University Maastricht, Maastricht, The Netherlands Monte Carlo (MC) simulations are potentially the most accurate and powerful techniques to calculate dose in radiotherapy, in addition to other quantities of interest, e.g. particle fluence. They are increasingly being used in treatment planning systems (TPS) for photon, electron and proton therapy. In addition, they are also increasingly encountered in preclinical research that involves precision irradiation of small animals, which nowadays use dedicated MC TPS available for radiobiology research. This lecture will cover the basics of MC particle transport: transport mechanisms, sampling from cross sections and definition of complex geometries. The advantage of track visualization and particle tagging will be demonstrated. The broad applications of MC will be discussed in modelling radiation detectors, modelling radiation sources (linear accelerators, proton beam lines, brachytherapy sources), dose calculation in cancer patients, and dose calculation in imaging panels for radiotherapy. In dose calculation in cancer patients, the subject of dose reporting as dose to water or dose to medium will be mentioned. MC simulations are also used to predict e.g. the emission of prompt gamma photons or annihilation photons in proton beams, to verify the proton range, which requires knowledge of nuclear interactions. Besides radiation dose, MC simulations can easily yield particle fluence spectra, which may be used for dose conversions, or as input for calculations of biological damage and relative biological effectiveness. Other specialized applications involve using MC for modelling precision irradiators and planning the irradiation of small animals for preclinical research. The accurate dose calculations of kV photon beams are needed to mimic human radiotherapy at the scale of small animals. Also the complex interactions of secondary electrons released in photon beams with the magnetic field inside an MR-linac, requires MC modelling for accuracy. MC dose calculations also lend themselves to modelling dynamic geometries. Limitations of MC methods are that they are still relatively slow, they exhibit statistical noise and they may express dose in unfamiliar units (dose to medium instead of dose to water).

Teaching Lecture: Update on molecular radiotherapy

SP-0558 Update on molecular radiotherapy G. Flux 1

1 The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Department of Nuclear Medicine, Sutton, United Kingdom Molecular radiotherapy was first developed following a meeting 80 years ago between the clinician Saul Hertz and the physicist Karl Compton after a lunchtime symposium on ‘What Physics can do for Biology and Medicine’. Radioiodine was synthesised and used to study thyroid metabolism and to treat both benign and malignant thyroid disease. In the first treatments, full dosimetry was performed by the physicist Arthur Roberts, using the best technology available at the time, 10 years before the development of the Anger camera. The use of radiotherapeutics for oncology continues to expand. In particular Ra-223, used to treat bone metastases from castration resistant prostate cancer, has now been approved in some countries. In the UK alone, treatments doubled in the year before approval. Administrations continue to be performed without imaging or patient specific dosimetry, although there are an increasing number of studies to show that this is feasible and that there exists a correlation between the absorbed doses delivered and response. A recent retrospective study of Re-186 HEDP demonstrated that survival was improved with the administration of higher activities and that the absorbed doses delivered to whole-body and to tumours correlated inversely with survival. This is due to the uptake being a marker of tumour burden, indicating the challenging potential of theragnostics. Lu-177 PSMA is being used increasingly for the treatment of bone metastases. Initial trials have shown safety and efficacy, and it is likely that its use will increase dramatically in the coming years. This follows results from the NETTER study where Lutathera was found to significantly improve PFS when compared with Sandostatin LAR (Octreotide LAR) in patients with advanced midgut neuroendocrine tumors (NETs). The treatment of liver metastases with Y-90 microspheres continues to expand. Internal dosimetry is playing a larger role for both glass and resin microspheres and a dosimetry software package has been developed by BTG for Theraspheres. Following many years of ad hoc treatment regimens, without specific international guidelines, a number of dosimetry-based clinical trials are now in progress or development, focussed on radioiodine treatment for thyroid cancer, Lu-177 DOTATATE for adult and paediatric neuroendocrine tumours, and I-131 mIBG for neuroblastoma. The European basic safety standards,

Teaching Lecture: RTTs roles and responsibilities to support future practice

SP-0560 RTTs roles and responsibilities to support future practice