ESTRO 36 Abstract Book

S1 ESTRO 36 _______________________________________________________________________________________________

SATURDAY, 6 MAY 2017

• Monte-Carlo simulation makes cavity theory redundant • Today’s Dose-to-Water Codes of Practice for Reference Dosimetry make CVTY unnecessary • Burlin or ‘General’ CVTY is hopelessly approximate and ought to be abandoned • Proton beam dosimetry requires the development of a new CVTY • Spencer-Attix CVTY removes the need for the BG assumption of negligible (secondary) electron fluence perturbation • Bragg-Gray theory breaks down in small-field megavoltage beams Teaching Lecture: High tech or low tech for metastatic disease, how does one decide and what is the cost- benefit? SP-0006 High tech or low tech for metastatic disease, how does one decide and what is the cost-benefit? Y. Van der Linden 1 1 Leiden University Medical Center LUMC, Department of Radiotherapy, Leiden, The Netherlands With ongoing improvements of the technical possibilities in radiation oncology and its widespread availability, the sky seems the limit, also for patients referred for palliative indications. But are these costly and time consuming protocols really helping our patients? In this talk, the necessity for high tech in palliative radiotherapy will be searched, comparing costs and benefits in terms of goals of palliative care, treatment outcome, quality of life, time consumption, and, also real costing. SP-0007 Gene editing: How this technique can be used to study radiation responses? L. Marignol 1 1Trinity Translational Medicine Institute, Translational Radiobiology and Molecular Oncology- Applied Radiation Therapy Trinity- Discipline of Radiation Therapy, Dublin, Ireland The personalisation of radiation therapy relies on the discovery of novel biomarkers predictive of treatment outcomes. The molecular classification of cancer with microarray and next generation sequencing have reduced time and costs associated with the generation of genetic profiles - but also the amount of genetic material required. Gene editing approaches using single-stranded RNA or DNA and/or CRISPR/Cas9 to disrupt or modify the DNA sequence of selected genes are attractive: the engineering of radioresistant cancer models enables the direct evaluation of the function of specific genes and regulatory elements in the radiation response. This approach has been particularly useful in the characterisation of the radiation-induced DNA damage response. Our increased ability to transfer these models into small animals and deliver highly conformal image guided irradiation further enable the robust evaluation of candidate markers. This lecture will discuss the potential and limitations of gene editing approaches in the identification of novel biomarkers of radioresistance. Teaching Lecture: Target delineation and target definition for Partial Breast Irradiation after closed cavity surgery and oncoplastic surgery Teaching Lecture: Gene editing: How this technique can be used to study radiation responses?

Teaching Lecture: The role of radiotherapy in small cell lung cancer -current status and future developments

SP-0001 The role of radiotherapy in small cell lung cancer -current status and future developments R. Dziadziuszko 1 The Maria Sklodowska-Curie Memorial Cancer Center, Warsaw, Poland

Abstract not received

Teaching Lecture: Immunotherapy

SP-0002 Immunotherapy G. Coukos Centre Hospitalier Universitaire Vaudois, Lausanne Vaud, Switzerland

Abstract not received

Teaching Lecture: MRI for RO physicists: what is what? QA geometrical distortions

SP-0003 MRI for RO physicists: what is what? QA geometrical distortions E. Paulson Medical College of Wisconsin, Mlwaukee, USA

Abstract not received

Teaching Lecture: Cavity Theory: separating the facts from the myths

SP-0005 Cavity Theory: separating the facts from the myths. A. Nahum 1 1 University of Liverpool, Physics, Henley-on-Thames, United Kingdom Cavity Theory (CVTY) is intended to yield the factor converting the reading of a dose-measuring instrument (or ‘dosimeter’) placed in an irradiated medium to the dose to that medium in the absence of the instrument i.e. D med / D det . All trainee medical physicists have been subjected to lectures on CVTY and may even have had to answer exam questions on it (and possibly some radiation oncologists and radiographers too!). This talk will attempt to sort out the facts from the misconceptions about CVTY. Many of the following statements will be examined critically: • Ion chambers are the only instruments that act as Bragg-Gray (BG) cavities and they only do so in megavoltage photon beams • BG theory does not require Charged-Particle Equilibrium (CPE) – the ‘proof’ is that it also works in electron beams • The density of the detector plays no role in its response • Expressions involving ratios of mass-energy absorption coefficients cannot be classed as cavity theory • The Fano theorem is a particular type of ‘cavity theory’ • Treatment planning algorithms do not involve CVTY concepts • All analytical expressions for so-called ‘perturbation factors’ are approximate