1
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Tony Lomax Centre for Proton Radiotherapy, Paul Scherrer Institute, Switzerland and
Department of Physics, ETH (Swiss Institute of Technology), Zurich
Proton (and light ion) therapy
9 field IMRT planProtons
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Overview of presentation
1. Passive scattering, discrete scanning and IMPT
2. Protons vs photons
3. Clinical results from PSI
4. Summary
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Why protons?
R.R. Wilson, Radiology 47(1946), 487-491
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
The Bragg peakE.g. Depth-dose curve for 177 MeV protons
0 5 10 15 20 250
1
2
3
Depth in water (cm)
Dos
e pe
r pr
oton
(nG
y)
Dose plateau where velocity is high
Dose peak where protons slow down
and stop
Width of peak dependent on
range straggling in medium and initial energy spectrum
Peak-to-plateau ratio 4-5
(depending on width of energy
spectrum)
Dose concentrated in small volume in Bragg peak.
2c)(
1
β∝
dR
dE
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
A mono-energetic proton Bragg peak is not very useful for treating anything other than the smallest tumours.
The problem of lateral field size and coverage in depth
To make protons useful , we need to spread out the dose laterally and along the beam direction.
Target volume
FWHM~9-11mm
σ~5-8mm
σ~3-5mm
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Extending the dose in depthThe ‘Spread-Out-Bragg-Peak’
target
2
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Extending the dose in depth
The range shifter wheelA rotating wheel with
varying thicknessThe range shifter wheel in action…
RS wheel rotates continuously in beam at ~3000 rpm
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Range-shifter wheel Scatterer
Collimator
Compensator
Target
Patient
Passive scattering in practice
Field specific aperture (collimator) matching projected
shape of target
The collimator
2D Projection of target along beam direction
• Each delivered field (incident direction of irradiation) requires specific collimator and compensator
• As range shifter is up-stream of scatterer(s), extent of SOBP is fixed across field
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Passive scattering in practice
Computer-milled compensators
(examples from Orsay)
Example collimator
Eye irradiation
Generally, a compensator and collimator are required for every field in the passive scattering approach
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Passive scattering in practiceSingle passively scattered
field
10cm
Fixed extent SOBP leads to poor sparing of normal tissue proximal to target
Three passively scattered fields
Conformation of dose can be improved through the use of multiple fields
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Target
Magnetic scanner
‘Range shifter’ plate
Patient
Proton pencil beam
Discrete scanningPAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Spot definition
Incident fieldIncident field
Spot selection
Spot weightoptimisation
Optimiseddose
Dose Calculation
Discrete scanning – a treatment planning example
3
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Note, each individual field is homogenous across the target volume
F1 F2
F3 F4
Combined distribution
Discrete scanning: Single Field, Uniform Dose (SFUD) mode
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
1 field
Discrete scanning
1 field
Passive scattering
3 fields 3 fields
Passive scattering and discrete scanning compared
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
The simultaneous optimisation of all Bragg peaks from all incident beams.
F1 F2
F3 F4
Combined distribution
Lomax, Phys. Med. Biol. 44:185-205, 1999
Discrete scanning: Intensity Modulated Proton Therapy (IMPT) mode
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
1 field
3 fields
IMPTPassive scattering
1 field
3 fields
1 field
SFUD
3 fields
The three ‘orders’ of proton therapy compared
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Example clinical IMPT plans delivered at PSI
Skull-base chordoma
4 fields
3 field IMPT plan to an 8 year old boy
3 fields
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Sources of protons for therapy
Cyclotrons
Relatively compact +
Continuous wave +
Fixed energy -
Higher amount of -contamination
Synchrotrons
Somewhat larger -
Pulsed -
Variable energy +
Less contamination +
Accel/Varian 250Mev
Cyclotron
3.5m Diameter
Loma Linda 250Mev
Synchrotron
6m Diameter
4
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
3.5m diameter
PSI gantry 1
7m diameter
PSI gantry 2
12m diameter
Loma Linda
15m diameter
Heidelberg
Proton treatment gantries are (and
will remain?) large…
Treatment gantries for proton therapyPAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Overview of presentation
1. Passive scattering, discrete scanning and IMPT
2. Protons vs photons
3. Clinical results from PSI
4. Summary
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Single posterior 160MeV proton field,
80cm long
No patching of divergent fields
required
Irradiation time ~ 10-15 minutes
No comparison necessary…!
1. Medulloblastoma (5 year old boy)PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Delivered single field plan 9 field IMRT plan9 field IMRT – second try
Factor 6 lower integral dose for protons
2. Desmoid tumor (12 year old boy)
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
4. Complex head and neck (IMPT vs Tomotherapy)
Tomotherapy 3 field IMPT
Widesott et al, IJROBP 2008
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
4. Complex head and neck (IMPT vs Tomotherapy)
Tomotherapy 3 field IMPT
Widesott et al, IJROBP 2008
5
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Tomotherapy IMPT Ratio (Tomo/IMPT)
Contralateral parotid 1 21.7% 4.8% 4.52
Ipsilateral parotid 1 41.5% 14.3% 2.9
Larynx 2 1.4% 1.9% 0.73
4. Complex head and neck (IMPT vs Tomotherapy)
NTCP averaged over all cases
Widesott et al, IJROBP 2008
1 End point – flow rate <25% after 1 year
2 End point - >= grade 2 enema after 15 months
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Anaesthesia equipment is mounted on the patient
table and monitored by video during the
treatment
A close collaboration between PSI
(PD Dr Beate Timmermann) and
KiSpi, Zurich (PD Dr Markus Weiss)
5. Pediatric cases (protons/IMPT vs IMXT)
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
5. Pediatric cases (protons/IMPT vs IMXT)
Work of Erik van der Boom
Average fields used:Protons: 1.9X-rays: 7.2
9 patients treated with protons at PSI compared to IMXT plans calculated retrospectively
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Serial organ
Serial organ
Serial organParallel organ Parallel organ
Parallel organ
Average EUD (overlapping) Average EUD (<25mm)
Average EUD (>25mm)
5. Pediatric cases (protons/IMPT vs IMXT)
Critical organ EUD’s as function of distance from PTV
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
5. Pediatric cases (protons/IMPT vs IMXT)
Non-target tissue integral dose
Average reduction in integral dose - 2.03 (1.5-2.7)
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Overview of presentation
1. Passive scattering, discrete scanning and IMPT
2. Protons vs photons
3. Clinical results from PSI
4. Summary
6
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
P04109 P04088
Prescription dose:
74 CGE
37x 2 CGE fractions
Brainstem surface 63CGE
Brainstem centre 54CGE
Optical structures 60CGE
1. Skull base chordomas and chondrosarcomasPAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Local control probability (n=42 Chordoma, n=22 Chondrosarcoma)
1. Skull base chordomas and chondrosarcomas
Ares et al, submitted to IJROBP 2008
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
1. Skull base chordomas and chondrosarcomas
Publication n Radiation Mean dose 5 year PFS
Debus et al 2000 37 Photons (stereotactic) 66.6 50
Cho et al 2008 19 Photons/ Gammaknife 60.0 40
Munzenrider and Liebsch 1999 169 Photons+
protons 72 64
Hug et al 1999 33 Photons+ protons 71 59
Noel et al 2005 100 Photons+ protons 67 54
Ares et al 2008 42 Active scanning protons 73.5 81
Gay et al 1995 46 Surgery NA 65
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
P07155P04070
2. Extracranial chordomas and chondrosarcomas
Prescription dose:
74 CGE
37x 2 CGE fractions
Spinal cord surface 60CGE
Spinal cord centre 54CGE
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Months
0
.2
.4
.6
.8
1
0 10 20 30 40 50 60
Without implant(n = 13)
Implants (n =13)
3-yr, 5-yr 100%
3-yr 69%5-yr 46%
Rutz et al, IJROBP, 67 (2007) 512-20
Local control rate
2. Extracranial chordomas and chondrosarcomasPAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Publication Indication n Median dose Local control
Weber et al (2007) Adult Sarcomas 13 69.4 74% (4 yrs)
Rutz et al (2008)
Pediatric and adolescent Chordoma/
Chondrosarcomas
10 74(66) 100% (36 months)
Timmermann et al (2007) Pediatric patients 16 50 75%
(1.5 yrs)
3. Other indications from PSI…
7
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Summary
• Proton therapy is a mature technique, with more than 50,000 patients treated world wide
• Spot scanning/IMPT provides improved flexibility and conformality in comparison to passive scattering
• IMPT is being delivered routinely at PSI with about 40% of all patients receiving IMPT as part of their therapy
• Initial clinical results with scanning are very favourable, and most new proton facilities will include scanning component
•Proton therapy is experiencing a ‘boom’ period in Japan, US and (continental!) Europe
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
P+
Thanks for your attention…
Why proton therapy in Switzerland?
PAUL SCHERRER INSTITUT
Tony Lomax, Mayneord-Phillips Summer School, July 2009
Gay et al 65% PFS at 5 years46 chordoma patients
67% (n=31) had total or near-total surgical resection
33% (n=15) had partial or sub-total resection
Ares et al 81% PFS at 5 years42 chordoma patients
0% (n=0) had total or near-total surgical resection
100% (n=42) had partial or sub-total resection
Gay et al: “Radiotherapy with high-energy particles, or by focussed radiation, is recommended if the tumour cannot be totally removed”
The ‘Brada’ argument
‘Proton therapy is no more effective than surgery…’