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ESTRO 36 2017
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SP-0098 What is the purpose of surgical
metastasectomy and do we achieve it?
T. Treasure
1
1
UCL Cancer Institute, Clinical Operational Research
Unit, London, United Kingdom
Is the purpose palliation? Earlier detection of metastases,
and selection for operations to remove them,
systematically targets asymptomatic patients - who have
no symptoms to palliate. There have been very many
follow-up studies but none document symptomatic
benefit. [Thorac Surg Clin 2016;26:79; Eur J Cardiothorac
Surg 2016;50:792] Intervention is explicitly offered with
curative intent.
Is cure often achieved? There has never been a study with
any form of control group to test survival difference. On
the other hand there have been multiple trials (16 RCTs to
date) of increasing intensity of monitoring to find
asymptomatic patients for metastasectomy with curative
intent. A systematic review capably done by an
international multidisciplinary team, including skills in
oncology, surgical research, data analysis and guideline
development, found no benefit but instead an excess of
harm done.[Br J Surg 2016;103:1259] Metastasectomy
appears to be an example of over diagnosis leading to
harm by over treatment. [Ending Medical Reversal.
Baltimore, Johns Hopkins University Press, 2015]
Scholars of the history of medicine recognise that over
time, disease states have been ‘framed’ and reframed as
the sophistication of diagnostic methods escalated from
clinical examination and morbid anatomy; through
microscopy, bacteriology, clinical chemistry and
haematology; and now to extraordinary advances in
imaging. This has resulted in a new diagnostic frame
‘oligometastatic cancer’ which is operationally defined by
excluding patients with more metastases than can be
treated by surgical resection or ablative methods.[J R Soc
Med 2012;105:242] This results in selection of patients at
the less aggressive end of the spectrum of metastatic
disease and hence naturally determined to be longer
survivors. So benefits of metastasectomy may be an
illusion. [JAMA Oncol 2015;1:787]
SP-0099 What is the indication and what is the aim of
clinical treatment: radiotherapy
E. Lartigau
1
1
Centre Oscar Lambret, Lille, France
Oligometastatic disease is considered Today to be
amenable to combined systemic and local treatment in
order to increase local control, decrease tumor burden
and potentially increase survival. Stereotactic body
radiotherapy has been successfully used in the treatment
of brain metastases for more than 3 decades and is now
widely used for bone, lung and liver metastases. For
example in our Department, the feasibility, efficacy, and
toxicity of SBRT as been evaluated for treatment of
unresectable hepatic or lung metastases regardless of
their primary tumor site for patients with a history of
aggressive systemic chemotherapy. Local control has been
demonstrated as excellent (66.1% at 2 years) even if
disease-free survival rates remains low (10%, 95% CI: 4–
20%). SBRT is well tolerated with few toxicities and
possible in aging patients. There is today a wide consensus
on the local role of SBRT in oligometastatic disease.
Current step is to optimize the combination with systemic
treatments (chemotherapy and targeted agents). A new
door has been more recently opened on the potential role
of early SBRT together with immunotherapy in order to
increase treatment response by neo antigens production
following high dose RT, or by immune activation after low
dose. Clinical studies are ongoing exploring this new path
ways.
SP-0100 Oligometastastic cancer: a therapeutic
challenge
K. Van der Hoeven
UMC St Radboud Nijmegen, The Netherlands
Abstract not received
Symposium with Proffered Papers: Targeting tumour
heterogeneity
SP-0101 Using heterogeneous brachytherapy dose
distributions to target tumour cell heterogeneity
R. Alonzi
1
1
Mount Vernon Hospital, Senior lecturer and consultant
in clinical oncology, Northwood Middlesex, United
Kingdom
Some tumour characteristics, such as hypoxia, vascularity,
cellular proliferation or clonogen density, can be mapped
geographically using functional imaging techniques or by
using
systematic
biopsies
with
subsequent
immunohistochemistry or molecular characterisation. The
ability to assimilate this functional information into the
radiotherapy planning process poses a number of
challenges, but the technology to achieve biological
conformity is widely available and routinely used in most
radiotherapy departments. The potential gains in
therapeutic ratio from the precision targeting of areas of
intrinsic resistance makes focused dose escalation an
exciting field of study and will be the principal theme of
this presentation.
Higher administered radiation doses can overcome
intrinsic radio-resistance. However, dose escalation to the
entire tumour volume may not always be possible.
Increasing the tumour dose will inevitably increase the
dose to the surrounding critical normal tissues leading to
worse acute and late toxicity. Focused dose escalation is
based upon the principle that areas of tumour with
relative radio-resistance can be overcome by
administering a higher biologically effective radiation
dose (BED). This can be achieved either by giving a higher
total dose or higher dose per fraction.
For focused dose escalation, brachytherapy offers some
major advantages over external beam techniques. One of
the key features of brachytherapy is that the irradiation
only affects a very localised area around each radiation
source as dose falls off rapidly, obeying the inverse square
law. This feature has been exploited for many years and
makes brachytherapy the most conformal of all
radiotherapy techniques. As long as the sources are
precisely placed within the tumour, there is minimal
exposure to radiation of healthy tissues further away from
the sources. This allows very high doses to be administered
to the target volume. Also, patient set-up and tumour
motion are less relevant because the radiation sources
move with the tumour and therefore retain their correct
position; this increases the confidence that the radiation
has been delivered in accordance with the required plan.
Brachytherapy plans are inhomogeneous by their very
nature, with high dose regions surrounding each source
and lower dose regions where there is maximum
geometrical separation between sources. By carefully
manipulating source positions and dwell times, the non-
uniform dose distribution can be shaped to match a
biological risk map. The brachytherapy implant technique
may have to be adapted to accommodate this.