When do we need to image in Radiation Oncology?
How do we image the treatment target ?
S / RxTh / CH
Work-up-staging
prognostic evaluation
Vincent GREGOIRE, M.D., Ph.D., Hon. FRCR
GTV/CTV
Selection/delineation
Head and Neck Oncology Program, Radiation
Oncology Dept. & Center for Molecular Imaging
and Experimental Radiotherapy, Université
Catholique de Louvain, St-Luc University
Hospital, Brussels, Belgium
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Functional Image-guided
IMRT
FDG
C-methionine
EF3 - F-miso - CuATSM
BFU - FLT
…
Early response
evaluation
Final response
evaluation
Early detection
of recurrence
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What do we need to image in Radiation Oncology?
How do we image ?
What is the accuracy of the various imaging
modalities ?
• Gross Tumor Volume: GTV
• Clinical Target Volume: CTV
• Internal Target Volume: ITV
• Planning Target Volume: PTV
• Planning Organ at Risk Volume:
PRV
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ICRU report 62, 1999
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Bayesian terminology for diagnostic imaging studies
“-”
TN
FN
NPV = TN/TN+FN
“+”
FP
TP
PPV = TP/TP+FP
ICRU report 50, 1993
The use of FDG-PET for the selection of
Target Volume: setting the scene
Disease status
“-”
“+”
Test
?
?
• Organ at Risk: OAR
Laryngeal SCC: T2-N1-M0
Q: unilateral vs bilateral
neck irradiation?
Sensitivity = TP/TP+FN
Specificity = TN/TN+FP
Disease
“-”
48
2
NPV = 96%
“+”
20
30
PPV = 60%
Sensitivity = 94%
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Specificity = 70%
Test
Test
Disease
“-”
“+”
A: highly sensitive
examination
“-”
“+”
“-”
25
25
NPV = 50%
“+”
4
46
PPV = 92%
Sensitivity = 65%
Specificity = 86%
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PET-FDG - N stage in NSCLC
Detection of metastatic disease in the neck
• Meta-analysis: n= 1236 patients (32 studies)
PET
• HNSCC (all sites)
N
Sensitivity
Specificity
Sensitivity
Specificity
Chin
30
78
81
56
86
Patz
42
83
82
43
85
Sasaki
29
76
98
65
87
Sazon
32
100
100
81
56
Scott
27
100
98
60
93
Steinert
47
89
99
57
94
Valk
76
83
94
63
73
• Neck dissection for all patients
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Kyzas et al., JNCI 2008
CT
Reference
Wahl
23
82
81
64
44
Vansteenkiste
68
93
95
75
63
Bury
50
90
86
72
81
Guhlmann
32
80
100
50
75
Total
456
87
92
62
76
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Detection of N2-N3 in NSCLC
The use of FDG-PET for the selection of
Target Volume: setting the scene
Oesophageal SCC
Q: should one increase
the CTV based on a
FDG-PET+?
A: highly specific
examination
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Vrieze, Haustermans et al., 2004
Pre-treatment staging of esophageal carcinoma:
distant lymph nodes
Potential added-value of PET for TV selection
Comparison between CT (MRI) and FDG-PET for nodal staging
Site
Specificity
CT
FDG-PET
CT
FDG-PET
Head and neck cancer
36-86%
50-96%
56-100%
88-100%
NSC lung cancer
45%
80-90%
85%
85-100%
Cervix carcinoma
57-73%1
75-91%
83-100%1
92-100%
Esophageal cancer
11-87%
30-78%
28-99%
86-98%
1
Van Westreenen, JCO, 2004
Sensitivity
?
CT or MRI
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Grégoire, 2004
Molecular Imaging across the board
Potential added-value of PET in oncology
• Lung carcinoma: more accurate delineation of the NSCLC
GTV
• Esophageal tumor: in progress…
• Brain tumor: 11C-Met in low grade glioma and meningioma
• Rectal tumor: promising data to be confirm…
• Cervix carcinoma: proof on concept only…
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Antoch et al., 2004
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Target selection and delineation
Betrayal of images
Target
This is not an
apple…
R. Magritte
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J. John, 1974
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5 cm
Image-Guided Radiation Therapy in HNSCC
Impact of imaging modality on CTV/PTV delineation
Macroscopy
18F-FDG
PET
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Daisne et al, 2003
150
CT-scan
FDG-PET
ANOVA: p<0.05
100
50
0
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Oropharynx (n=10)
Average (± sem) volume (cc)
5 cm
CAT Scan
Average (± sem) volume (cc)
5 cm
Larynx/hypopharynx (n=9)
200
250
200
CT-scan
FDG-PET
ANOVA: p<0.01
150
100
50
0
GTV
CTV
PTV
GTV
CTV
PTV
Geets et al, 2003
Image-Guided Radiation Therapy in HNSCC
Validation protocol in locally advanced HNSCC
Impact of imaging modality on dose distribution
CT-based target volume
Apport de l'imagerie fonctionnelle par Tomographie
par Emission de Positrons (TEP) dans le ciblage biologique
par radiothérapie de conformation (3D-CRT)
et par modulation d'intensité (IMRT) de tumeurs ORL
FDG PET-based target volume
Use of functional imaging with PET for target volume
delineation in 3D-CRT/IMRT for head and neck tumors
Prof. V. Grégoire, UCL St-Luc, Brussels, Belgium
Prof. E. Lartigau, COL, Lille, France
Dr. JF Daisnes, Cliniques St-Elisabeth, Namur, Belgium
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CT
MRI (T2)
FDG-PET
PRE-R/
(Week 2)
4D-IMRT
WEEK 3
(Week 4)
WEEK 5
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The Cathedral of Rouen
C. Monet, 1894
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Image-Guided Radiation Therapy in HNSCC
The 4th dimension …
PET image segmentation during RxTh
FDG-PET
UG 4mm
SBR
Raw image
0 Gy
50 Gy
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Image processing
BG 6mm + deconvolution
W&C
Geets et al, 2003
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Image segmentation
Impact on dose distribution
Impact on TV delineation
Classic CT-based planning Adaptive PET-based planning
P<0.001
P<0.001
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Geets, 2007
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Geets, 2006
How frequently? …
F-Miso PET-CT
Spatially “complex” target
FDG
FLT
CuATSM
A: dayx (before treatment)
B: dayx+3 (before treatment)
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Jeraj et al, 2010
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Zhixiong, Ling et al., 2008
Effect of image resolution
2,5 mm
2,0 mm
Effect of resolution
2,7 mm
3,0 mm
r²
0.88
AR 100 µm
0.84
Mosaic PET
1,5 mm
0.86
0.87
3,5 mm
0.86
0.84
% vol
Mouse T ø
0.0
7.0
8.7
10.0
11.0
12.1
12.7
13.1
13.9
14.5
0.0
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13.9
17.5
20.1
22.1
23.8
25.3
26.6
27.8
28.9
30.0
N. Christian, 2010
15.0
Human T ø
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N. Christian, 2010
Image-Guided
Therapy in HNSCC
TakeRadiation
home message
Comparison 18F-FDG / 14C-EF3
• TV selection depends on the sensitivity and the specificity of
the various imaging modalities
• TV selection is thus highly tumor-site dependent.
• TV delineation with various imaging modalities requires
proper validation methodology
• Use of imaging during RxTh for TV re-delineation needs
further validation.
• Biological IGRT based on new PET tracers should remain in
the research arena.
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N. Christian, 2010
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