Download Image-Guided Radiation Therapy

IMRT, IGRT AND ADAPTIVE
RADIOTHERAPY FOR THE HEAD
AND NECK
Madhur K Garg, MD
Clinical Director and Associate Professor,
Montefiore Medical Center
Albert Einstein College of Medicine, USA
Before: conventional
planning
• use of 2D anatomical borders from anatomical
landmarks on films
Before: conventional
planning
Improved delivery systems
 Linear Accelerators
Improved delivery systems
• Multileaf
collimators:
Customized, computerprogrammable motorized
blocks
•Attached to linear
accelerators
Intensity Modulated
Radiotherapy (IMRT)
 Separation of beam into beamlets
 Delivery with linear accelerator or tomotherapy
3D Conformal with blocks
IMRT field
Images taken from www.sifatip.com.tr
IMRT plan – parotid sparing
Optic Apparatus sparing
But with more precise
delivery…
 Come opportunities
 Decrease volume irradiated to highest dose
 Morbidity and patient compliance
 and dangers:
 Possibility of geographic miss
 patient movement increases chance that target area will not
get target dose
 Tumor may move relative to bony anatomic landmarks
 Increased integral dose
 Radiation-induced cancer
New Paradigm : IGRT
 Image-Guided Radiation Therapy
 Frequent imaging in treatment room
 Permits adjustments accounting for change in target:




Position
Movement with respiration
Size
Shape
Advantages of IGRT
 Accurate daily patient set-up
 Conformal avoidance of radiosensitive structures
 Dose sculpting around complex shaped target
volumes
“WYSIWYG”
 Adaptive treatment planning: ability to adapt
today’s treatment to yesterday’s delivered dose
pattern • Tumor response adaptation
• Target and normal structures shifting adaptation
IGRT: techniques
 Portal imaging
 Ultrasound
 Markers/fiducials
 “CT on rails” in Linac room
 Tomotherapy
 Cone-beam CT
 MV and kV
Brachytherapy
 Is this really IGRT?
 No, but…
 Accounts for tumor
motion by physical
association of
radiation source with
tumor
Fluoroscopy
 Used with 2D planning
 Beneficial for intra-fraction motion~ swallowing
Portal Imaging
 In most centers,
taken weekly
 May not reflect
true, daily patient
treatment
Imaging: kV vs MV
 kV x-rays with greater contrast
 MV useful for use in patients with orthopedic and
dental artifacts
MV
image
kV
image
On-Board Imaging (OBI)
 Refinement of portal
imaging technique
 Allows frequent 
daily check of setup
 Time-intensive!
Cone-beam CT fused to Planning CT
“Toys”
CT on rails in treatment room
Varian Trilogy
Tomotherapy
• Uses 6MV beam for scanning
and to deliver therapy
– Higher integral dose
Cyberknife
• Tracking of fiducial
markers and bony anatomy
• 5 degrees of freedom
• Not practical for multiplefractionated therapy
Head and Neck Adaptive
Radiation Therapy
 What can happen?
 Setup error / patient movement
 Weight loss
 Tumor shrinkage
 Normal tissue shrinkage
~20% had ~ 5 mm shift on 2D and
>3 mm shift on CBCT
 50 patients with head and neck cancer
 C-spine angle (CSA) = angle by line projected from
posterior C2 to line projected parallel to C6.
Neck Moves Too!
• CSA decreased less in patients undergoing postoperative
RT (1.1°±1.4°) compared with patients treated
definitively (2.95°±2.26°)
 Bite block with fiducial array
and optical tracking system
 20 patients
 10 of these were
prospectively enrolled in
clinical trial of daily
positioning
 Treated with 3DCRT
 10 IMRT patients
Hong et al.
 Measured 6 degrees of freedom
 Large variance in vector displacement!! (6mm)
• 14 patients with head and neck cancer
– 8 patients with shoulder mask
– 6 patients with short-length mask
• Gross primary and/or cervical nodal disease measuring at
least 4 cm
• CT-on rails 3x weekly during entire RT course with
integrated CT-Linac
– Median 16 scans/patient
Zhang et al.
 Analyzed setup uncertainties
in 3 bony regions of interest:
 C2 vertebra
 C6 vertebra
 Palatine process of maxilla
(PPM)
Zhang et al.
 in lateral direction, less
correspondence between C2 and
maxillae (PPM)
 implies existence of independent
head rotations (roll).
 poor correlation in SI shifts between
PPM and C2
 implies head nods (pitch)
Zhang et al.
Zhang et al.-Results and
Conclusions
 Positioning mouthpiece decreased variation in SI axis
 Short-facemask did not have an effect on variation
 Rigid translational shifts are not difficult with present
immobilization systems
Ahn et al
Montefiore-Einstein Experience
RANDOM POSITIONAL VARIATION WITH
TREATMENT PROGRESSION DURING HEAD
AND NECK RADIOTHERAPY
Introduction
 There are 3 degrees each of


translational freedom (X, Y, Z) and
rotational freedom (pitch, roll and yaw)
 Taking the skull, mandible, and each of levels C1-C7 into account,
there are at least 54 separate degrees of freedom in movement of
the head and neck
Patient characteristics:
Histology, operative status, and stage
Methods:
Patient set up
 23 sequential head and neck radiotherapy patients underwent serial
CT scans (total 93 scans).
 Immobilization was achieved with a custom-fitted short face
thermoplastic mask and shoulder pulls.
 Setup was reproduced during planned rescans at approximately 11, 22
and 33 fractions.
Methods:
Motion Measurement
 Points that were taken include:
 bilateral cochlea
 incisive foramen
 bilateral mental foramen
 center of the base of the odontoid process
 bilateral transverse foramina from each of C1-C7, and the
midpoint of the posterior-most extension of the spinous process
Mandible Roll
Roll at C1
Neck Pitch
at C6
Lordosis
Results:
Translation and Rotation
 Both translational and rotational parameters exhibited large
variations with a wide range
 Both rotational and translation movement of the skull was
independent of the lower cervical spine movement
 Changes in scoliosis and lordosis of the cervical spine were
independent of skull movement
Results:
Position variability and set up
 No strong correlation with weight loss or skin separation at multiple
levels: position variability does not depend on anatomy changes.
 Positioning variability was largest in the mandible and in the lower
cervical spine: parotid and lower neck node doses may suffer the
greatest variations.
 Lack of correlation between variations in position and fraction
number: different than previously thought, patient set up accuracy
does NOT improve over time.
Results:
Predicting Changes
 Multiple linear regression analysis did not reveal one or any
combination of surrogate factors (fraction number, weight loss,
changes in skin separation at C1, mandible, C4, or midpoint of tumor
in the neck) that could adequately explain changes in rotational or
translational parameters
Anatomic Changes
Normal Structures and Target
Schwartz et al: J Oncol. 2011
Schwartz et al: J Oncol. 2011
Elstrom et al: Acta Oncologica. 2010
Gregoire et al: Radiother Oncol. 2010
Gregoire et al: Radiother Oncol. 2010
Schwartz et al: J Oncol. 2011
Impact on Dose distribution
Positional and anatomic changes
Loss of “shoulder”
Harari et al: Int J Rad Onc Biol Phys. 2005
Loo et al: Clin Oncol. 2010
Loo et al: Clin Oncol. 2010
 13 locally advanced, Stage III or IVA/B ca of H&N
 Dosimetric study
 Retrospective
 Attending chose which patients would be rescanned
 3 patients replanned for weight loss (average 11%)
 8 patients replanned for both weight loss and tumor
volume loss
Hansen et al.
Montefiore Medical Center/Albert
Einstein Experience
 Prospective study, 23 patients
 Treated with 33 fractions to 66-69.96Gy with
simultaneous integrated boost
 rescan with CT simulator at 11, 22, 33 fractions
 89 CT scans
 129 unique CT-plan combinations
 Patients were replanned if unacceptable PTV coverage or
dose to normal structures
Adaptive Planning
 Patient with unknown primary
 Based on original plan, 45Gy isodose to the cord
Adaptive Planning
 With shrinkage in tumor size, greater than tolerance
dose is now reaching to cord
 Hotspot is greatly increased
Adaptive Planning
 With new plan, cord dose is now within tolerance
Adaptive Planning
 Same patient, original plan
Adaptive Planning
 With tumor shrinkage, greater dose now to the
pharyngeal mucosa (100% = 70Gy)
Adaptive planning
 With replan, dose to mucosa is now decreased
 S1 = planning scan
 S2 = fraction 11 (approximate)
 S3 = fraction 22 (approximate)
 S4 = fraction 33 (approximate)
lateral separation at BB's
14.00
separation (cm)
12.00
10.00
S1
S2
S3
S4
8.00
6.00
4.00
2.00
0.00
1
0.80
vector shift in skin iso (BBs) versus
bony anatomy isocenter
vector displacement
(cm)
0.70
0.60
S1
S2
S3
S4
0.50
0.40
0.30
0.20
0.10
0.00
1
 Shifts in lateral
separation at
isocenter occur as
treatment
progresses
 The tattoos move as
relative to anatomic
isocenter as
treatment
progresses
• increase in volume
at S2 likely reflects
radiation-induced
inflammation
Changes without re-plan
Montefiore Medical Center/Albert Einstein
 15 patients replanned
 3 patients replanned twice
Montefiore Medical Center/Albert Einstein
Surrogate predictor for the need for replan?


Weight loss, positional shifts analyzed
No clear correlative factor seen
rescan Right parotid V26/original plan V26
versus % weight loss
R² = 0,065
300,00
250,00
% of original R parotid V26

200,00
150,00
100,00
50,00
0,00
-10,000
-5,000
0,000
5,000
10,000
% weight
loss
15,000
20,000
25,000
Montefiore Medical Center/Albert Einstein
Dosimetric parameters and
positional variation
Dosimetric and anatomic changes
Reasons for re-plan: any
correlation?
Reason for re-plan
Conclusions
 The head and the neck move in relation to and
independent of each other
 Dosimetric changes that can occur with
positional and anatomic variation:




Cord dosage ~ 3-5 %
Brainstem dosage ~ 3-5 %
Parotid dosage ~ 10-15%
PTV coverage ~ 5-7 %
Conclusions
 No single positional or anatomic variable predicted for
need for a replan
 There is contribution from both inconsistent patient
position (independent random events) and anatomic
changes (gradual and predictable)
 Isocenter and 3 point triangulation (orthogonals) may
not be adequate in IMRT
 IGRT using CT should be frequently employed
Future directions
 To what extent can IGRT be automated?
 Currently labor-intensive from MD standpoint
 Not compensated by insurance
 How does one completely immobilize the head
with the neck?
 With tumor shrinkage and weight loss
 When to replan?
And does it all matter?
Quality of Life Data
Global Health Status
100.00
Physical Functioning
80.00
60.00
40.00
20.00
6 Month Post
3 Month Post
1 Month Post
Week 6
Week 5
Week 4
Week 3
Week 2
Week 1
Pretreatment
0.00
D Blakaj, M Fang et al: ARS 2011
Acknowledgments
 Radiation Oncology
 Shalom Kalnicki, MD, FACRO
 Chandan Guha, MD, PhD
 Peter Ahn, MD
 William Skinner, MD
 Otorhynolaringology
 Radiation Physics
 Ravi Yaparpalvi, MS






Dennis Mah, PhD
Dinesh Mynampati, MS
Paola Scripes MS
Joe Li, MS
Jin Chen, CMD
Ekeni Miller, CMD
 Richard Smith, MD
 Bradley Schiff, MD
 Medical Oncology
 Missak Haigentz, MD
 Nursing
 Hilda Haynes, ANP
 Cathy Sarta, NP
 Yoko Eng, NP