ESTRO 36 Abstract Book

ESTRO 36

5–9 May 2017

Vienna, Austria

SATURDAY, 6 MAY 2017

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

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

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.

med

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

• 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

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.

Teaching Lecture: Gene editing: How this technique can

be used to study radiation responses?

SP-0007 Gene editing: How this technique can be used

to study radiation responses?

L. Marignol

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.