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Beasr Treatment Using SIS Proton Beam Therapy
Citation preview
Stacey Schmidt, B.S., RT(T), CMD
Manager, Medical Dosimetry
CDH Proton Center
CDH Cancer Center
Delnor Cancer Center
Warrenville & Geneva, IL
Simulation, Planning, and Delivery of
Breast/Chest Wall Treatment Using Uniform
Scanning Proton Beam Therapy
2
Course Objectives
After participating in this session, you will be able to:
• Explain the benefit of using protons to treat stage III disease or
previously treated patients.
• Identify patient selection criteria.
• Discuss the simulation process and immobilization device
selection.
• Describe techniques used in treatment planning.
• Demonstrate the dosimetric advantages of Uniform Scanning
(US) proton therapy over photon therapy.
• Illustrate the daily imaging and treatment delivery processes
specific to US protons
What cancer types are typically
treated with protons?
4
Common indications for proton therapy
• Pediatric tumors of the CNS or elsewhere
• Brain tumors
• Spinal cord tumors
• Base of skull chordomas or chondrosarcomas
• Prostate cancer
• Ocular melanomas
5
Less common, yet emerging indications for treatment
with proton therapy
• Lung cancer
• GI cancers
• Head and Neck cancers
• ……and now, Breast cancer
6
Protons for Breast Cancer? Preposterous!
Past roadblocks include:
• Concerns over target movement/reproducibility
• Lack of skin sparing with Protons
• Photons have been getting the job done very well for
years!
These are valid concerns even with improved
techniques. However, it was worth looking into for a
select subgroup of these patients.
Why use protons?
8
Red Journal article from PSI in 2010
9
Stage III Breast Cancer patients
The most difficult breast cancer sub-type to treat with traditional x-
ray/photon radiation therapy, due to the inclusion of axillary,
supraclavicular, and internal mammary lymph nodes.
These photon plans
are generally not very
homogeneous, and include
significant dose to the
Ipsilateral lung and heart
(particularly left
sided patients).
10
Retreat Breast Cancer patients
These patients have
typically already
received significant
dose to the
ipsilateral lung
and/or heart, and
therefore it is even
more important to
spare excess dose
to these structures.
Selection Criteria
12
ProCure specific selection criteria required for use of
protons in breast cancer patients
• Stage III disease either post mastectomy or
lumpectomy AND require treatment to ipsilateral
supraclavicular, axillary, and internal mammary lymph
nodes
• Or, must have had RT to the same side previously
• Must not have a pendulous breast or metal expanders
in reconstructed implants
• Must be able to lie with arms up or down for
approximately 45 mins
13
Patients can be treated off or on protocol
• All patients treated so far have been on our Registry
protocol. PCG – Reg – 001
• Patients have the option to enroll in the PCG cardiac
sparing BRE008 and be treated on protocol. These
patients are required to start txmt 9 weeks after
surgery or 8 weeks after the initiation of
chemotherapy. They must also have a CT
Angiography study, which is used to help contour
specific cardiac vessels for dose reporting.
14
Patients can be treated off or on protocol
The Simulation Process
16
Gantry or Inclined Beam treatment room?
• Before selecting the appropriate immobilization
device, the determination must be made whether or
not the patient will be treated on the gantry or in one
of the inclined beam treatment rooms.
• Differences:
– Gantry room has most flexibility with treatment angles
– Inclined beam room has fixed gantry angles of 30 or 90
degrees, but our technique for this room allows for most
enface setup.
17
Gantry
18
Incline Beam Line
19
Gantry setup
Patient must be positioned
with both arms up in a
‘particle-friendly’ long vac-
loc or alpha cradle device.
Chin is up, with head rotated
away from the treated side.
Bilateral breast/chestwall
patients are treated on the
gantry, and the chin must
also be extended. There is
no head rotation for these
patients.
20
Inclined Beam setup
Patient is positioned with both
arms down, and the ipsilateral
arm slightly akimbo.
Depending on the patient’s
anatomy, a wedge may be
inserted under the ipsilateral
side to achieve ‘enface’
position of the
breast/chestwall
Patient’s chin is also up, and
head turned away from the
affected side.
21
Other views of the IBL setup
22
Additional step in IBL Simulation Procedure
• Before pouring chemicals into the alpha cradle, a quick scan
must be done through the breast tissue to determine the angle of
the breast will be enface with the 30 degree gantry angle. A
reproducible, enface breast position needs to be achieved for the
treatment in the IBL.
• If the breast/cw angle is less than 30 degrees a small Styrofoam
wedge will be needed. This will be placed under the patient’s
affected chest wall area to turn the patient so that the
breast/chestwall is on a 30 degree angle.
• If the breast angle is more than 30 degrees the patient may need
to have the hips rolled toward the affected side to decrease the
angle.
23
Patient Marks
• Once the breast box has hardened, start making the
treatment marks on the patient and box.
• Start with head position first: use the laser and have it
intersect the patient’s lips. Once this is done use a
marker and draw a line on the box to match; label as
lip line. If an arm is up mark on the patient’s elbow/
tricep area.
• Find the SSN and set sagittal laser to boney anatomy.
Try to make sure the SSN and end of sternum match
with the laser.
• Mark a three point set up on patient and box; about at
the end of the rib cage.
24
Demonstration of patient marks
25
CT Scan Specifications
• Scan from top of head to below inframammary fold.
• 1.25 mm slice thickness
• 65 FOV used to get entire treatment device in scan (necessary for
checking for device collisions and to make sure a beam isn’t
going through the device)
• Cradle will need to be offset in bore to have all of affected side in
scan. Indexing bar with offset is utilized.
• No 4D scan is necessary if magnitude of motion is less than
5mm. Breathing motion being in same direction as beam path.
First patients were done with 4D, but has been discontinued, as it
has been demonstrated to no longer be a concern and we want to
minimize excess dose for the patient.
• MD places wires for clinical borders and on scar.
The Treatment Planning
Process
27
Fusion
• Fusions required:
– Not usually, unless patient is on BRE-008 protocol. Then
fusion with CT Angiography study is require for cardiac
vessel delineation.
– If patient was previously treated, then a deformable fusion is
done between the two treatment planning CTs. The
patient’s previous electronic DICOM radiation dose files are
requested for help with dose summation.
28
MD Contours
• MD will contour the CTV_50.4, which is comprised of the
ipsilateral supraclavicular nodes, chestwall/breast tissue, axillary
lymph nodes, and internal mammary lymph nodes.
• RTOG guidelines for breast/chestwall and nodes are utilized, with
the exception that the entire ribs and chestwall are not included.
These areas were included in RTOG guidelines for simplicity, and
were not used to define regions of disease involvement, paths of
disease spread, nor regions at risk of reoccurrence.
• If patient is on the BRE008 study, the MD will also contour the
RCA, LAD 1st diagonal branch, and the LAD 2nd diagonal branch.
• If the patient is to have a tumor bed or scar boost, the MD will
draw these structures as well.
29
Chestwall CTV and Coronary Artery contours
30
Chestwall CTV on a Multi-Planar View
31
Dosimetrist Contours
• R & L Lungs, plus Total Lung structure
• Heart
• Thyroid
• Esophagus
• Ipsilateral Brachial Plexus
• Skin
• Ipsilateral Humeral Head
• Patient External, including treatment devices
32
Planning Techniques Utilized
• Regardless of which treatment room is used, a
matching fields, 3D forward-planned, uniform
scanning proton treatment plan is utilized.
– 2 fields used for the supraclavicular and superior axillary
node region
– 2 fields used for the breast/chestwall region
Gantry IBL
33
Planning Techniques Utilized
• Why 4 beams per day????
– Robustness!
• Minimizes risk from daily setup error
• Allows for more homogeneous dose distribution,
minimizing hot/cold spots at the junction
• Spreads the surface dose between the 2 beams per
section, in order to spare the skin full dose from one
beam entry point.
34
Beam Selection Criteria – Gantry Room
• Gantry Technique
– Want to utilize beams that are angled slightly off enface
35
Gantry plan treatment angles
36
Beam Selection Criteria - IBL
• Beam options are limited, therefore we position the
patient to make the angles optimal, having the beams
enter the patient as enface as possible.
– 1 set of Left or Right anterior oblique matching fields at
G30T0
– 1 set of Anterior Superior Oblique matching fields at
G30T270
37
Beam Selection Criteria - IBL
LAO
beams
ASO
Beams
38
Beam Selection Criteria - IBL
Demonstration
of 1 set of the
ASO matching
fields to cover
the entire CTV.
39
IBL plan treatment angles
40
Planning Techniques Utilized
• In both techniques, all 4 fields are treated per day,
incorporating 2 matchlines between the
supraclavicular and chestwall/breast regions.
• Fields are matched at depth using a dosimetric, not
geometric match line.
• Junction selection, isocenter placement, and air gaps
tightened as much as possible are crucial for these
types of plans.
41
Isocenter Placement and Snout Size Restrictions
• Largest snout size 25 cm
• The CTV extends from the most superior
supraclavicular node to inferiorly just below the
implant or 2 cm below the former inframammary fold.
42
Isocenter Placement and Snout Size Restrictions
• In order to make the most efficient treatment possible,
isocenters are selected so that both the superior and
inferior volumes share the same X and Z coordinates,
and only an inferior Y shift is necessary on a daily
basis.
• It is also crucial to select an X position so that the
breast/chestwall region is centered in the snout, and
that there is room to add adequate aperture margin.
43
Isocenter Placement and Snout Size Restrictions
44
Junction Selection
• Crucial to achieving an optimal treatment plan with
well-behaved compensators.
• Select junction in region where the supraclavicular
nodes end and the chestwall volume begins.
• Want to keep deep portion of nodal volume separate
from breast/chestwall region.
• Drastic changes in depth within a compensator can
cause hot spots and steep ridges.
45
Junction Selection
• Since there are 4 total fields treated daily, two sets of
fields are matching, and the junctions are about 1 cm
apart.
Matchline 1
Matchline 2
46
Optimized Air Gaps
• It is important in proton therapy to keep as tight of an
air gap between the end of the compensator and the
patient’s skin as much as possible.
• Tighter air gaps = sharper lateral penumbra
• Sharper lateral penumbra = matchlines that are easier
to optimize!
• However, this is not always achievable, due to the size
of the chestwall/breast volume, and the ability to fit it
in the snout.
47
Optimized Air Gaps
• Take away: keep it as tight as possible, but make sure
your PTV will fit into the snout with adequate margin
for lateral coverage
Air Gap = 10 cm Air Gap = 25 cm
48
Plan Optimization
• Once all beams are added, isocenters are set, air gaps
are finalized, and the junction areas are determined,
then:
– Apertures are added to all beams, and optimized so 95% of
the PTV is covered laterally
– Compensators are added, and tapered to remove any ridges
greater than 2 cm
– Ranges and modulations are set to cover the CTV by the
100% ISL. Dose coverage specifications are that the D95%
of the CTV must equal 100% of the Rx, and the D99% must
equal 95% of the Rx.
– Matchlines are tweaked so that the hot/cold areas are equal
in size
49
Plan Optimization
• Each beam is optimized so that the CTV coverage
constraint is met
• Then, uncertainties are added to the range and
modulation for each beam
– Our center uses 2.5% + 2 mm for the CT HU to stopping
power conversion uncertainty and cyclotron delivery
precision uncertainty
• Organs at risk are now evaluated
50
Target Dose Constraints
51
Organs at Risk Dose Constraints
Dosimetric Advantages of
Protons
53
In Isodose Distributions
Proton Doses
Photon Doses
54
In Isodose Distributions
Proton Doses
Photon/E-
doses
55
In Isodose Distributions
Proton Doses
Photon/E- Doses
56
In Isodose Distributions
Proton Doses
Photon/E- Doses
57
In the Dose Volume Histograms
Proton
Plan
Photon/
E- Plan
Photon/E- Plan
Lt Breast
58
In the Dose Volume Histograms
Proton
Plan
Photon/
E- Plan
Rt Breast
Proton Plan
Photon/E- Plan
59
In the Dose Volume Histograms
Proton
Plan
Photon/
E- Plan
Lt Breast
Proton Plan
Photon/E- Plan
The Treatment Delivery
Process
61
Patient Alignment
• Alignment Process
– Align patient’s mouth with superior marks on cradle
– Line up both superior and inferior patient marks with vac-loc/alphacradle marks
– Align 3 point tattoos
– Align anterior tattoo with SSN and Navel for straightening
62
Daily Setup Fields
• Once the patient is aligned, the first setup field is
imaged. This is done to make sure that the arm,
head/chin, and humeral head are in the right position.
At this point any directional shifts may be applied for
the set up field.
• The setup fields are typically at 0 or 90 degree gantry
angles.
63
Daily Setup Fields
64
Treatment Order – Gantry Room
• After filming at site setup, both supraclavicular fields
are treated first.
• Then, an isoshift, generally just in the Y direction
inferiorly, is performed.
• Finally, after filming post shift, both chestwall fields
are treated.
65
Treatment Order – Inclined Beam Room
• Start with Supraclavicular field with Table 0 Gantry 30,
shift inferior
• Then, treat the breast/chest wall field at Table 0 Gantry
30.
• Swing couch, and treat breast/chest wall field at Table
270 Gantry 30. Then, shift superior.
• Finally, treat the supraclavicular field with Table 270
Gantry 30
66
Daily IGRT Shift tolerances
• Tolerances:
– Site Setup/Supraclavicular field:
• anatomy within 2mm in X, Y, & Z
• Allow 1 Degree pitch, roll, & rotation
– Matching Chestwall field
• Anatomy within 4mm in X & Z
• No Y, pitch, roll, or rotation, in order to maintain the
geometry for the match
67
Treatment Times, Setup Films taken
• Avg.tx.time table time thus far=49.5 min
• Avg.# of setup x-rays= 3.1
• Total #breast patients treated to with these techniques
to date: 18
68
Conclusions
• Will continue to offer proton therapy to these
subgroups of breast cancer patients, as the organ
sparing benefits have convinced us that this is a
worthwhile option for these patients.
• Continue to look for ways to make the entire planning
process more efficient.
• Other indications:
– Partial Breast treatment for early stage – treated 1 patient
per protocol thus far
– Pencil Beam Scanning on the Gantry for the Stage III and
retreat patients
69
References
• PCG BRE-008 Cardiac-Sparing Post-Mastecomy Protocol
• Ares, et al, Postoperative Proton Radiotherapy for Localized and
Locoregional Breast Cancer: Potential for Clinically Relevant
Improvements, Int. J. Radiation Oncology Biol. Phys. 76, No. 3,
pp. 685–697(2010)
• Fagundes, et al, Abstract poster presentation at PTCOG 2013
• H. Paganetti: Range ncertainties in proton therapy and the impact
of Monte Carlo simulations, Phys. Med. Biol 57 R99-R107 (2012)
• RTOG Breast Cancer Atlas for Radiation Therapy Planning:
Consensus Definitions
70
Acknowledgements
• Entire Physics and Dosimetry teams at ProCure
Chicago and Cadence Health.
• The Breast Team: Rachel Sewell, RT(T), Dawn Smith,
RT(T), Megan Marshall, RT(T), Jennifer Mitchell, RT(T),
Stephanie Hufnal, RT(T) Minu Vachachira, RT(T),
Lauren Curran, RT(T), Hilary Deeke RT(T), Lindsey
Havron, RT(T)
Thank you for your attention!!!
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