World Congress of Brachytherapy 10-12 May, 2012 - Estro-events.org

1
INTRODUCTION
C.HaieMeder
Institut Gustave Roussy, Radiation Oncology, Villejuif, France
Target volume determination is probably one of the most challenging
issues in radiation oncology, at the era of highly targeted
radiotherapy. BT has to face this challenge, even in a more accurate
way, as BT physical and biological properties provide the most
conformal and normal tissue sparing radiotherapy technique. To reach
this goal, BT has benefited from recent advanced imaging
technologies. The use of 3D techniques for BT dosimetry has increased
during the recent years, mainly CTbased, but also using MRI, PETCT
and ultrasound. Image guidance improves tumor and organs at risk
visualization, and their relationship with the applicator (in
gynecological tumors), representing the basis for 3D and 4D BT
treatments plans.
Prostate BT was developed using ultrasound guidance. The accuracy
of seed placement and dosevolume parameters has significantly
improved with more sophisticated imaging modalities. Emerging
techniques in ultrasound and MRI modalities, including functional
imaging, as well as 3D digital mapping, allow for more accurate
disease characterization with improvement in staging and
management of the tumor. This issue represents the basis for dose
painting.
In cervical cancer BT, MRI based adaptive BT enables 4D target
volume optimization with appropriate dosevolume constraints for
organs at risk. First clinical series report an improvement in local
control which seems to translate into a survival benefit. Ultrasound is
an evolving field and is currently under study. The value of functional
MRI or PETCT is also under investigation.
In endometrial cancer, postoperative BT has become the new
standard in intermediaterisk patients. In this situation, there is a
potential for imagebased individualization which is under
investigation.
Apart from these two main tumor sites, BT using new imaging
modalities has been developed in other fields, such as breast, head
and neck and endoluminal (bronchus, oesophagus).
In the last decade, the use of imaging modalities integrated into the
BT procedure has led to a significant increase of BT all over the world.
The use of images also led to the development of BT guidelines,
allowing multiinstitutional studies, contributing to clinical research
and scientific publications.
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ROLE OF FUNCTIONAL IMAGING
B. Carey 1
1
St James Institute of Oncology The Leeds Teaching Hospitals NHS
Trust, Radiology, Leeds, United Kingdom
The evolution of the art of brachytherapy into a precision form of
scientifically based radiation therapy owes much to major
developments in imaging and computer technology over the past
decade. Brachytherapy offers the most conformal of all forms of
radiotherapy and is designed largely around the intricate relationships
between radiation dose delivered, target volume and fractionation
regimes. Traditional brachytherapy planning techniques have
benefited enormously from morphological imaging techniques such as
Computed Tomography, Magnetic Resonance Imaging and Ultrasound.
Tumour volumetricbased radiation planning based on better anatomy
has much improved our ability to target malignant tissue whilst
sparing nonmalignant tissues. 3D target localisation has been
successfully modelled around a hierarchy of expanding treatment
volumes based on the demonstrable tumour morphology as well as
allowing for technical imperfections and variations in treatment
delivery. A new paradigm for treatment planning and radiation
delivery is now becoming possible with the ability of medical imaging
to define areas of varying functional activity within the presumed
tumour mass.
A new probability envelope is emerging based on our recognition of
the altered biological and molecular processes occurring in tumour
tissue. A biological target volume can be identified generally as a
subset or subsets of the morphological target volume and offers a
potentially modified approach for brachytherapy. These new
functional maps of the tumour provide the basis for a very innovative
approach to radiation treatment using much more selective planning
and treatment delivery techniques. Locating and quantifying areas of
cellular and molecular disruptions within the tumour mass offer the
potential to individualise the radiotherapy treatment and the highly
conformal and adaptive nature of brachytherapy perhaps stands to
gain most from these new functional imaging techniques.
FDGPET has become an established imaging technique in oncology
and is becoming increasingly integrated into treatment planning
processes for several common tumour sites. Newer isotopes are being
developed to further expand the depth and range of our knowledge of
tumour behaviour and will offer future targets for brachytherapy dose
delivery and modifications. Functional MRI is providing us with
additional physiological surrogate targets for dose modifications.
Newer developments in functional Ultrasound and CT will also
enhance the information available to the radiation oncologist and
yield a much more detailed map of tumour architecture and function.
The inherent goal of brachytherapy is to safely deliver adequate
radiation to those areas of tumour tissue that are considered
necessary based on our current understanding of tumour biology and
radiation response. Functional imaging offers us a way forward in
identifying subvolumes of tumour that may benefit from different
radiation regimes based on different measurements of tumour
response. Furthermore, we have the future potential to noninvasively
assess these treatment responses in terms of altered cellular and
molecular processes as well as altered tumour morphology. These are
exciting times for functional imaging based brachytherapy.
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PET IMAGING IN BRACHYTHERAPY
V. Lowe 1
1 Mayo Clinic, Brachytherapy, Rochester, USA
Positron Emission Tomography (PET) is now being widely in the
evaluation of many types of malignancy. Multiple studies have
demonstrated the utility of PET in oncologic imaging in better staging
of disease, earlier treatment response assessment and better
characterization of recurrent disease over what can be done with
anatomic imaging methods alone. The availability metabolic
substrates other than FDG makes PET imaging attractive in some
tumors that have been otherwise poorly evaluated by FDG. This talk
will discuss the use of Choline PET imaging with discussion of how it
can be used in conjunction with brachytherapy
While prostate cancer cells have not ubiquitously shown FDG avidity,
increased choline uptake has been a more consistent finding on PET
imaging. Cancer cells have more rapid cell proliferation than normal
cells. New cells require the building blocks for cell membranes.
Choline is a watersoluble essential nutrient grouped with B
complex vitamins—that is vital for a) cell membrane structure and
signaling b) synthesis of neurotransmitters and c) general metabolism.
[ 11 C]choline is a synthetic form of choline that releases positrons by
beta decay that can be visualized by PET. [ 18 F]choline is another
radionuclide version of choline that can also be used in PET imaging.
The increased accumulation of these agents by prostate cancer in any
part of the body is a reliable way to determine the extent of prostate
cancer.
Choline PET can be use in two different treatment time points in
prostate cancer related to brachytherapy. At initial staging,
confirmation of localized disease to the prostate bed can be
performed using choline PET. Choline PET provides high accuracy for
the detection of distant metastasis. This can aid in treatment
planning. Choline PET may be most useful in the situation of
definitively treated prostate cancer with the discovery of biochemical
recurrence. One of the clinical dilemmas of biochemical recurrence of
prostate cancer is the how to decide on an optimal treatment