SUMMARY
OF RESEARCH ACTIVITY:
Volume Definition and Exchange of Contours
(Sutton and Chelsea)
Stefano Gianolini, Elizabeth J Adams,
James L Bedford, Cephas D Mubata, Rollo Moore, Alan Nahum, AMargaret
Bidmead; in collaboration with David P Dearnaley, Urology and Testicular
Cancer Unit. Source of funding: Urology and Testicular Cancer Unit,
MRC, The Royal Marsden
An independent DICOM agent has been set up to allow CT data
to be transferred between different commercial treatment-planning
systems. Computer software has been written to allow the transfer
of contours in conjunction with these images and this work is now
being used with the data from the quality assurance study of the
RT01 national MRC prostate trial. The development of "Guinnes"
has improved the flexibility of this system and more treatment-
planning system communication is now available. It has provided
links to radiobiological modelling software written by members of
the Dose Modelling Group.
Reduction of Heart Dose in Breast Radiotherapy
Colin A Nalder, John Pettingell, Chris
Fall; in collaboration with L Viviers, GM Ross, Section of Radiotherapy.;
Source of funding: The Royal Marsden
A new CT planning position for breast radiotherapy with
the use of a commercial breast board system is being investigated
to try to reduce heart irradiation in breast radiotherapy. The
addition of MLC conformal shielding, without compromise of PTV
coverage, reduces dose to the heart significantly. Evaluation
of the contouring device "OSIRIS" is being undertaken
by comparison with CT scan data of patients in the new treatment
position. Both accuracy of contour and prediction of lung position
are being assessed.
Comparison and Optimisation of Breast
Plans with Patient in CT position
Sara Alonso-Arrizabalaga, Catharine
Clark, Colin A Nalder, John Pettingell, Chris Fall; in collaboration
with L Viviers, GM Ross, Section of Radiotherapy
Source of funding: The Royal Marsden, Varian Oncology Systems
CT data obtained for the previous study is also being used
for the production and evaluation of optimised treatment plans
for uniform and boost, breast irradiation, whilst sparing lung
and cardiac surfaces. Various treatment plans have been produced
for contoured PTV's and a comparison of techniques is underway.
Prostate Dose Escalation Study - RT01
[Project No.1460]
Rollo Moore, Caroline Lamb, Claire
Banks, Sara Alonso, Maragret Bidmead, Colin Nalder, Carole Meehan,
John Pettingell, Cephas Mubata; in collaboration with DP Dearnaley,
Urology and Testicular Cancer Unit. Source of funding: The Royal
Marsden, Urology and Testicular Cancer Unit, MRC
The quality assurance analysis of the three-dimensional
treatment-planning process for RT01 patients is centred at The
Royal Marsden. The Radiotherapy Physics Group is acting as the
reference centre for quality assurance and is evaluating data
from all the participating centres. A detailed quality-assurance
program has been developed and site visits have been be made to
all participating centres. In addition, treatment plans and dose-volume
histograms are being collated and evaluated from the six different
computer planning systems in use at the different centres for
this trial.
Stereotactic Radiotherapy
Kevin Burke, Colin Nalder, T. Ajithkumar.
Source of funding: The Royal Marsden; Neuro-Oncology Unit
Stereotactic radiotherapy continues to be offered as a
standard form of treatment for brain tumours. A dedicated radiotherapy
research registrar is in post to investigate further applications
of the stereotactic system and to evaluate geometric uncertainties
involved in patient set-up and treatment delivery using DRR's
and electronic portal imaging. This data will contribute to geometric
set-up uncertainty data being reviewed by the BIR in the context
of ICRU 62.
Brachytherapy Research and Development
Margaret Bidmead, Colin Nalder, Margarida
Fragoso,; in collaboration with PR Blake, D Barton, Gynaecology
Unit. Source of funding: The Royal Marsden, C UK
New software which allows CT input of patients with brachytherapy
applicators in place is being evaluated. This software also has
different methods of dosimetry calculation which are under development
in collaboration with the manufacturer. Patients who have had
previous radiotherapy to the pelvis can be re-treated with the
intra-operative placement of catheters for the afterloading of
high-dose-rate iridium to give a dose distribution specifically
designed to conform to the tumour bed whilst sparing surrounding
normal tissues. A series of selected patients are being treated
by this method, which is continuously evolving and patient follow-up
is being maintained.
Portal Imaging
Carole Meehan, Cephas Mubata, Kevin
Burke, Margaret Bidmead
Source of funding: The Royal Marsden
Continuing commercial collaboration with Varian Oncology
Systems has provided new image matching software which is being
evaluated and compared with existing software. Implementation
of reference images direct from the new Acuity Simulator form
part of this recent evaluation. Use of DRR's for prostate and
brain verification are now routine.
Assessment of Immobilisation Shells
for the Treatment of Head and Neck Patients with IMRT
Mandy Humphreys, Helen Convery,
Margaret Bidmead, Cephas Mubata
Source of funding: The Royal Marsden
Verification of patient position using an orthogonal pair
of images has been developed to assess the reproducibility of
immobilisation with particular reference to the neck region. This
is to assess the "goodness of fit" of the radiotherapy
shell around the shoulder area and thus the immobilisation of
the spinal cord, in preparation for IMRT treatment delivery. When
identifying nodes and possibly escalating dose to these areas
immobilisation is crucial. Orthogonal images are acquired on the
first five days of treatment and matched. If positional reproducibility
is good then images are taken at weekly intervals. The high resolution
of the amorphous silicon detector allows accurate comparisons
of anatomical position to be made.
Evaluation of Monte-Carlo Dose Computation
in a Commercial Treatment-planning System
Colin Nalder, Cephas Mubata,
Joao Seco, Stefano Gianolini, Alan Nahum, Margaret Bidmead, David
Dance. Source of funding: The Royal Marsden
The extensive development work already done by the Monte-Carlo
group on Monte-Carlo based dose computation using the EGS/BEAM
system is now ready for clinical evaluation via a comparison of
Monte-Carlo based plans with those generated in the CADPLAN (Fulham
Rd) and PINNACLE (Sutton) commercial treatment planning systems.
A user-friendly interface to these TPSs is under development.
A number of treatment plans will be analysed in this manner, in
terms not only of differences in 3D dose distribution (relative
and absolute) and Dose-Volume Histograms but also using so-called
biological models employing the GUINESS dose distribution analysis
software (developed by Dr S Gianolini).
Simulation of Intensity-Modulated Radiotherapy
by Monte-Carlo
Joao Seco, Alan E Nahum, Steve
Webb, Margaret Bidmead, David R Dance; in collaboration with Frank
Verhaegen, NPL, Teddington
Source of funding: EPSRC, The Royal Marsden, The Institute
Monte-Carlo simulation is being applied to all the stages
in the delivery of Radiotherapy by intensity-modulated high-energy
photon beams: the creation of the intensity variation by means
of a multileaf collimator, whether statically or dynamically,
comparison of this with the desired photon-fluence profile, and
the resulting dose distribution in the patient and its differences
compared to the predictions of the treatment-planning systems
at Sutton and at Fulham Rd. This project builds on the accelerator-modelling
work done by Dr F Verhaegen and uses the cluster of PCs developed
by Dr P Love during 1999-2000. The software platform is currently
the EGS/BEAM system, though more efficient alternatives are being
explored.
Development of 3D Models for the Accurate
Integration of CT-based Brachytherapy and External-beam Treatment
Planning
Margarida Fragoso, Margaret
Bidmead, Alan Nahum; in collaboration with F Verhaegen, NPL, Teddington;C
Deehan, Medical Physics, Leicester; D Hill, Medical Physics Department,
GKT, London. Source of funding: The Institute
Patient position is radically different between brachytherapy
for cervical cancer involving caesium sources and external-beam
therapy. It has been shown that this "anatomical distortion"
can be only partially "corrected" using sophisticated
voxel-based image deformation software developed by the medical
imaging research group at Guy's Hospital. Monte-Carlo methods
are being applied to the brachytherapy dose distributions, thus
accounting for both the detailed geometry of the sources and the
effect of patient heterogeneity described by CT; a model of the
phase-space of particles on the surface of an applicator has been
implemented as the starting point for the simulation of the radiation
transport in the full heterogeneous geometry of the patient. Radiobiologically
based "correction" of the brachytherapy dose delivery
in order that it may be added to the 2Gy fractionated external-beam
delivery will also be carried out.
Monte-Carlo Simulation of Ionisation
Chamber Response using the EGSnrc Code
Alan E Nahum, Margarida Fragoso. Source
of funding: The Institute
Recent improvements to electron transport within the EGS
code system (namely the option of switching between condensed-history
and interaction-by-interaction or analogue simulation of the elastic
scattering events close to media boundaries) promise to remove
the previous difficulties encountered when simulating ion chamber
response in megavoltage photon and electron beams. In particular
previous versions of EGS4/PRESTA failed to predict the measured
change in response of an aluminium-walled chamber in a Co-60 beam
due to the addition of extremely thin layers of dag (graphite
in liquid form). We are currently performing simulations of this
chamber geometry using the EGSnrc code; preliminary results indicate
that all the problems have not yet been resolved.
A phase I dose escalation study of the
use of Intensity Modulated Radiotherapy (IMRT) to treat the prostate
and pelvic nodes in patients with localised prostate cancer.
Catharine Clark, Teresa Guerrero-Urbano,
John Staffurth, Cephas Mubata, Carole Meehan, Elizabeth Miles,
Margaret Bidmead, David Dearnaley
Source of funding: The Royal Marsden, Varian Oncology Systems
The Cadplan Helios inverse treatment-planning system has
been used to plan simultaneous boost IMRT for patients with cancer
of the prostate and pelvic nodes. This is part of a phase I dose
escalation trial to investigate the benefits of increasing the
dose to the pelvic nodes from 50 Gy to 55 Gy and then to 60 Gy.
The second level of escalation has begun and the third level is
envisaged to begin in early 2003.
A phase I/II dose escalation study for
treatment of patients with carcinoma of the thyroid and cervical
nodes
Catharine Clark, Teresa Guerrero-Urbano,
Elizabeth Miles, Cephas Mubata, Margaret Bidmead, Mandy Humphreys,
Helen McNair, Kevin Harrington and Chris Nutting. Source of funding:
The Royal Marsden, Varian Oncology Systems
External beam radiotherapy for cancer of the thyroid poses
a difficult challenge, due to the proximity of the target volume
to the spinal cord. IMRT allows the sparing of the spinal cord
whilst achieving superior dose coverage to both the thyroid and
the surrounding involved nodes. The aim of this study was to design
a class solution suitable for delivering IMRT on our 2100C/D Varian
linac, as well as establishing methods for verifying the dose
and fluence for this technique. This work found that IMRT offers
improved target homogeneity in patients with thyroid carcinoma
as well as reducing the dose to the spinal cord. In particular,
the increased minimum dose within the PTV should increase tumour
control probability. We have designed a 5-field IMRT technique
with asymmetric posterior oblique fields which provides sparing
of the spinal cord whilst maintaining acceptable coverage of the
thyroid and PTV targets. Following this study, treatment of thyroid
patients using this IMRT technique has started as part of an approved
clinical trial. Dose escalation from the current level of 58.8
Gy to 66.6 Gy to the thyroid will be the next step in this trial.
Intensity Modulated Radiotherapy (IMRT)
to improve target coverage, spinal cord sparing and allow dose
escalation in patients with cancer of the larynx
Catharine Clark, Teresa Guerrero-Urbano,
Elizabeth Miles, Margaret Bidmead, Cephas Mubata, Kevin Harrington,
Peter Rhys Evans and Chris Nutting
Source of funding: The Royal Marsden,
Varian Oncology Systems
An investigation has been carried out into the potential
for IMRT to improve the coverage of the target and the sparing
of the spinal cord in radiotherapy treatment of the larynx and
bilateral cervical lymph nodes. In an initial study, conventional
and IMRT plans were produced for six patients to treat the larynx
to 65Gy and the lymph nodes to 50Gy. The potential to escalate
the dose to both the larynx and the nodes was investigated for
the IMRT plans. It was found that IMRT offers improved target
homogeneity and reduces irradiation of the spinal cord. This sparing
of normal tissue structures is sufficient that significant dose-escalation
of both the larynx and lymph nodes may be possible without any
predicted increase in normal tissue complication probability.
Following this study patients are now being treated in the clinic.
Once the treatment technique has been established then the dose
will be escalated to 67.2 Gy to the larynx PTV and 56.0 Gy to
the lymph nodes in 28 fractions.
A phase III Parotid sparing trial for
patients with head and neck cancer
Catharine Clark, Teresa Guerrero-Urbano,
Elizabeth Miles, Colin Nalder, Cephas Mubata, Margaret Bidmead,
Kevin Harrington, and Chris Nutting
Source of funding: The Royal Marsden,
Varian Oncology Systems
A study has started to investigate treating head and neck patients
whilst sparing the parotid glands. This will be part of a Phase
III trial. The patients will be randomised between a conventional
and an IMRT technique. In an initial study, conventional and IMRT
plans were produced for five patients to treat the high dose region
to 65Gy and the lymph nodes to 54Gy in 30 fractions. It was found
that IMRT offers improved target homogeneity and significantly
reduces irradiation of the parotid glands. This is expected to
improve the patients' quality of life by reducing the incidence
of dry mouths which is a common side effect of parotid irradiation.
An IMRT planning and QA protocol was designed. Following this
study patients are now being treated in the clinic.
A randomised pilot study of high dose
hypofractionated conformal radiotherapy in localised prostate
cancer
Catharine Clark, Teresa Guerrero-Urbano,
Elizabeth Miles, Colin Nalder, Sara Alonso, Caroline Lamb, Margaret
Bidmead, John Staffurth and David Dearnaley
Source of funding: The Royal Marsden,
Varian Oncology Systems
A randomised trial is underway to treat patients with prostate
cancer using a simple step and shoot technique. Recent studies
on the radiobiology of prostate cancer have suggested that shorter
courses of radiotherapy giving higher doses at each treatment
(hypofractionated radiotherapy) may give improved cancer control
for the same level of radiation related side effects. There are
three arms to this trial to treat the prostate to 74, 60 and 57
Gy in 37, 20 and 19 fractions respectively. The aim is to treat
the prostate PTV to the appropriate total dose and two additional
margins of 5mm and 10mm to 96% and 80% respectively. A planning
study was undertaken to investigate how these plans should best
be carried out. It was found that a two segment technique using
three or four gantry angles generally produced the isodose levels
required. No extra quality assurance, beyond that usually done
for conformal planning, is needed.
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