ESTRO 36 Abstract Book

S295

ESTRO 36 2017

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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.

6. Li et al. Cancer Res 2016;76(7):1770–1780.

7. Kucharzewska et al. Proc Natl Acad Sci

2013;110(18):7312–7317.

Teaching Lecture: Update on molecular radiotherapy

SP-0558 Update on molecular radiotherapy

G. Flux

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,

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

SP-0559 Basics, implementations, applications and

limitations of Monte Carlo dose calculation algorithms

F. Verhaegen

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: RTTs roles and responsibilities to

support future practice

SP-0560 RTTs roles and responsibilities to support

future practice

M. Coffey

Coffey Mary, Dublin, Ireland