Download F-18 FDG PET-CT fusion in radiotherapy treatment planning for

F-18 FDG PET-CT FUSION IN RADIOTHERAPY TREATMENT
PLANNING FOR HEAD AND NECK CANCER
Mary Koshy, MD,1 Arnold C. Paulino, MD,3 Rebecca Howell, MS,1 David Schuster, MD,2
Raghuveer Halkar, MD,2 Lawrence W. Davis, MD1
1
Department of Radiation Oncology, Division of Nuclear Medicine and Molecular Imaging,
Emory Clinic and Emory University, Atlanta, Georgia
2
Department of Radiology, Division of Nuclear Medicine and Molecular Imaging,
Emory Clinic and Emory University, Atlanta, Georgia 30322
3
Methodist Hospital/Baylor College of Medicine, Department of Radiation Oncology,
6565 Fannin St., MS-DB1-077, Houston, TX 77030. E-mail: [email protected]
Accepted 30 November 2004
Published online 16 March 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/hed.20179
Abstract: Background. The fusion of fluoro-2-deoxy-Dglucose – positron emission tomography (FDG-PET) with CT
scans has been shown to improve diagnostic accuracy and
staging in non-small cell lung cancer. We report on the influence
of PET-CT fusion on the management of patients with head and
neck cancer.
Methods. Thirty-six patients with intact primary head and
neck cancers treated with radiation therapy (RT) received PETCT as part of treatment planning. Workup before PET-CT included a contrast-enhanced CT scan of the head and neck and
chest X-ray; patients with nasopharyngeal and paranasal sinus
primary tumors also underwent MRI.
Results. Changes in TNM score and American Joint Committee on Cancer stage occurred in 13 patients (36%) and five
patients (14%), respectively, based on PET-CT. RT volume and
dose were altered in five patients (14%) and four patients (11%),
Correspondence to: A. C. Paulino
Dr. Mary Koshy is a recipient of a 2004 Young Oncologist Travel Grant
Award from the American Radium Society.
Abstract presented in part at the 86th Annual Meeting of the American
Radium Society, May 1 – 5, 2004 at Napa Valley, California.
B 2005 Wiley Periodicals, Inc.
494
respectively. Five patients initially were seen with carcinoma of
unknown primary, and PET-CT confirmed oropharyngeal primary
tumors in two. PET-CT data also detected a synchronous lung
cancer in one patient.
Conclusion. PET-CT fusion may have a significant impact
on staging and determination of RT treatment volume and dose.
A 2005 Wiley Periodicals, Inc. Head Neck 27: 494 – 502, 2005
Keywords: PET-CT; head and neck cancer; functional imaging;
radiotherapy treatment planning; staging
Fluoro-2-deoxy-D-glucose – positron emission tomography (FDG-PET) has recently played an important role in the staging process for head and
neck cancer. FDG-PET identifies primary lesions,
nodal disease, distant metastasis, and secondary
tumors in patients with head and neck cancer. In
15 studies of head and neck cancer published since
2000, the reported sensitivity of nodal detection
with PET was 87%, and specificity was 95%, in
contrast to CT/MRI, which was found to have
a sensitivity of 77% and a specificity of 87%.1 – 6
In small series of patients with head and neck
PET-CT Fusion in Radiotherapy Treatment Planning for Head and Neck Cancer
HEAD & NECK
June 2005
cancer, PET has also played a significant role in
the detection of suspected recurrence and residual disease, with a sensitivity and specificity of up
to 100%, in contrast to the 75% sensitivity and
80% specificity of CT/MRI.7 – 10 Recently, combined
PET-CT scanning has been introduced with the
advantage of providing anatomic information of
the CT scan in conjunction with the functional
information of the PET scan. Historically, PET information for T classification has not been as
superior as for nodal staging, primarily because of
a lack of anatomic information. PET-CT provides
critical structural information about the tumor
and its relationship to adjacent soft tissue and
surrounding bone, muscle, and cartilage and allows functional imaging to become a component
of radiation treatment planning. This fused image provides both the anatomic delineation of the
tumor and biologic information, which can aid in
identifying target volumes.10
The use of PET-CT fusion in non-small cell
lung cancer (NSCLC) has been found to have a
significant impact on staging, changes in patient management, and radiation therapy (RT)
treatment volumes.11 – 16 In addition, the use of
PET-CT fusion has been shown to result in more
accurate staging of both the primary tumor and
nodal disease compared with PET alone, CT
alone, and visual correlation of PET and CT.17,18
More accurate methods of staging may lead not
only to more precise RT volumes and doses but
also to overall clinical patient management. Here,
we report on the clinical impact of PET-CT fusion
on the management of patients with intact head
and neck cancer. Specifically, we looked at how
PET-CT altered the TNM and American Joint
Committee on Cancer (AJCC) stage, as well as RT
volume and dose.
MATERIALS AND METHODS
The subjects of this single-institution
retrospective study included 36 consecutive patients seen at our department with intact squamous cell carcinoma of the head and neck region.
The primary site location was oropharynx in
17 patients, nasopharynx in five patients, larynx
in four patients, paranasal sinuses in three patients, oral cavity in two patients, hypopharynx
in two patients, and unknown primary in three
patients. Table 1 illustrates the sites and subsites within the head and neck. There were eight
women and 28 men, with a mean age of 56 years
Patients.
Table 1. Primary site location in 36 patients undergoing
PET-CT fusion.
Primary site
Frequency
Oropharynx
Tonsil
Base of tongue
Valleculla
Soft palate
Nasopharynx
Larynx
Supraglottis
Glottis
Paranasal sinuses
Maxillary sinus
Hypopharynx
Posterior pharyngeal wall
Oral cavity
Floor of mouth
Oral tongue
Unknown primary
Total
17
(9)
(4)
(2)
(2)
5
4
(2)
(2)
3
(3)
2
(2)
2
(1)
(1)
3
36
Abbreviation: PET, positron emission tomography.
(range, 32 – 80 years). All patients except one
were initially seen with a new diagnosis of
malignancy of the head and neck and underwent routine workup with clinical examination,
contrast-enhanced CT of the head and neck, and
chest X-ray. Patients with unknown primary cancers metastatic to cervical nodes had endoscopic
biopsies and tonsillectomy. Patients with nasopharyngeal and paranasal sinus primary tumors
also underwent MRI of the head and neck. One
patient had a history of carcinoma of unknown
primary tumor treated with right neck dissection
3 years previously and was seen with recurrent
disease and a primary tumor in the vallecula. For
the 36 patients, most were initially seen with advanced locoregional disease. The PET-CT scan
was acquired for AJCC TNM staging and for radiation treatment planning before treatment
onset.19 At the time of FDG-PET imaging, no patients had clinical or radiologic evidence of distant metastases or synchronous tumors by CT
scan and MRI of the head and neck and chest
X-ray. At our institution, all patients with head
and neck cancer requiring RT receive intensity
modulated radiation therapy (IMRT). All of the
patients were treated with IMRT technique,
except for one patient with metastatic disease to
the esophagus, who received palliative threedimensional conformal RT. Three patients underwent neck dissections before chemoradiation.
Platinum-based chemotherapy was given concurrently with RT in 31 patients (86%).
PET-CT Fusion in Radiotherapy Treatment Planning for Head and Neck Cancer
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495
Table 2. Tumor (T) classification before and after PET-CT.
Pre – PET-CT
classification
T0
T1
T2
T3
T4
Total
No. patients by post – PET-CT classification
No. patients
T0
T1
T2
T3
T4
Upstage ratio
Downstage ratio
5
7
7
5
12
36
3
—
—
—
—
3
2
7
—
—
—
9
—
—
6
—
—
6
—
—
—
4
—
4
—
—
1
1
12
14
2/5
0/7
1/6
1/6
0/12
4/36
0/5
0/7
0/6
0/6
0/12
0/36
Abbreviation: PET, positron emission tomography.
444 MBq) of 18F FDG was injected, and 45 to
60 minutes was allowed for uptake before patient
imaging. Patients were instructed to minimize
any talking, chewing, swallowing, or movement of
the head, because these activites can influence
muscular uptake in the masticator muscles, tip
of the tongue, face, neck, and larynx.20,21 Non –
contrast-enhanced CT imaging for attenuation
correction anatomic correlation was performed
first from the vertex of the skull to below the
kidneys. An RT head holder was used for
immobilization. First, the CT scan was completed
using 180-mA tube current, 140-kV tube voltage,
0.5-second tube rotation, helical pitch of 1:1, and
reconstructed slice thickness of 4.25 mm. The CT
portion was acquired in less than 30 seconds.
Neither IV nor oral contrast was used. Immediately after the CT scan, a PET emission scan was
acquired starting at the skull vertex with an
acquisition time of 5 minutes per bed position
with a one-slice overlap at the borders of the
14.6-cm field of view. Data were reconstructed
using OSEM iterative reconstruction with two iterations and 28 subsets. Postprocessing with a
post filter at 5.45-mm full width at half maximum
(FWHM), and a loop filter at 3.91-mm FWHM on
a 128 128 matrix was then carried out. Images
All patients initially received a planning CT simulation
scan (with 100 mL intravenous [ IV ] contrast injected at rate of 2 mL/second) on the General
Electric (GE) light speed scanner (General Electric, Milwaukee, WI) in the radiation therapy department. The planning volume was scanned with
2.5-mm increments. Patients were simulated in
the supine position and immobilized with a head
mask and scanned in the RT position. These CT
imaging studies were subsequently fused to the
hybrid PET-CT images.
PET-CT scans were performed either on the
same day or within 1 week of the CT simulation
scan. Before the PET-CT, all patients were required to fast for 4 hours but were encouraged to
drink water. All imaging and data acquisition was
performed on an integrated PET-CT system
(Discovery LS, GE Medical Systems, Milwaukee,
WI), and patients were scanned in the same position (immobilized with a head mask) as they
were in their radiation simulation CT scan. The
PET/CT integrates an eight-slice helical CT scanner (Light Speed Plus; General Electric) and a
PET scanner (Advance NXi; General Electric).
CT and PET images are hardware coregistered
in a single session. Typically, 10 to 12 mCi (370 –
CT Simulation and PET-CT Scan Procedure.
Table 3. Nodal (N) classification before and after PET-CT.
No. patients by post – PET-CT classification
Pre – PET-CT classification
N0
N1
N2a
N2b
N2c
N3
Total
No. patients
N0
N1
N2A
N2B
N2C
N3
Upstage ratio
Downstage ratio
5
8
2
14
5
2
36
3
1
2
1
—
—
7
1
7
—
—
—
—
8
—
—
—
—
—
—
0
1
—
—
12
—
—
13
—
—
—
1
5
—
6
—
—
—
—
—
2
2
2/5
0/8
0/2
1/14
0/5
0/2
3/36
0/5
1/8
2/2
1/14
0/5
0/2
4/36
Abbreviation: PET, positron emission tomography.
496
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Table 4. American Joint Committee on Cancer stage before and after PET-CT.
No. patients by post – PET-CT stage
Pre – PET-CT stage
No. patients
I
II
III
IVA
IVB
IVC
1
2
10
21
2
0
36
1
—
—
—
—
—
1
—
1
1
—
—
—
2
—
—
8
—
—
—
8
—
—
1
20
—
—
21
—
—
—
—
1
—
1
—
1
—
1
1
—
3
I
II
III
IVA
IVB
IVC
Total
Upstage ratio
Downstage ratio
0/1
1/2
1/10
1/21
1/2
0/0
4/36
0/1
0/2
1/10
0/21
0/2
0/0
1/36
Abbreviation: PET, positron emission tomography.
were viewed on a Xelerus (GE Medical Systems)
workstation. PET and CT data sets were then
sent by means of a DICOM (Digital Imaging and
Communication in Medicine) protocol to the CT
simulation workstation for image coregistration.
The radiation planning CT was then fused to the
CT of the hybrid PET-CT, and these data were
used for dose calculation and sent to the
ECLIPSE treatment planning system (Varian,
Palo Alto, CA). Three or more reference anatomic
landmarks were matched and fused, with a
maximum acceptable error of 5 mm.
Table 5. Summary of changes in management with PET-CT.
Patient no. and disease site
Pre – PET-CT TNM
(AJCC stage)
Post – PET-CT TNM
(AJCC stage)
1 Maxillary sinus
T3N0M0 (III)
T4aN0M0 (IVA)
2 Unknown primary
(base of tongue)
T0N2bM0 (IVA)
T1N2bM0 (IVA)
3 Unknown primary
(valleculla)
T0N1M0 (III)
T1N1M0 (III)
4 Tonsil
T2N2bM0 (IVA)
T2N2cM0 (IVA)
5 Larynx
T2N0M0 (II)
T2N2cM1 (IVC)
6 Tonsil
T2N1M0 (III)
T2N0M0 (II)
7 Soft palate
T4bN2cM0 (IVB)
T4bN2cM1 (IVC)
8 Hypopharynx
T4aN2cM0 (IVA)
T4aN2cM1 (IVC)
9 Hypopharynx
T1N0M0 (I)
T1N0M0 (I) Hypopharynx and
T4N2M0 NSCLC (IIIB)
Management changes
Increase in PTV to encompass tumor identified
on PET
Decrease in initial PTV as primary site was found
(nasopharynx not included); primary tumor in
oropharynx received higher RT dose
Decrease in initial PTV as primary site was found
(nasopharynx not included); primary tumor in
oropharynx received higher RT dose
Increase in PTV to include PET identified tumor
extension to deep muscles of tongue and
contralateral (right) neck disease; increase in
RT dose to right neck
Diffuse metastatic disease and bilateral neck
metastasis seen only on PET; RT intent
changed from curative to palliative; RT
volume decreased to include only
esophageal mass causing dysphagia; and
RT dose decreased to palliative 30 Gy.
No change in RT dose or volume; based on the
finding of N0 status with PET, a decision to not
give chemotherapy and treat with RT alone
Curative to palliative intent; no change in
initial RT dose or PTV; change in patient’s
chemotherapy regimen
Curative to palliative intent; no change in
initial RT dose or PTV; change in patient’s
chemotherapy regimen
This patient had a 2.5 cm RLL cavitating lesion
seen on PET-CT; lung biopsy revealed
adenocarcinoma, and the patient was taken
to surgery; Pathology revealed a T4N2M0
stage IIIB NSCLC
Abbreviaitons: PET, positron emission tomography; PTV, planning target volume; RT, radiation therapy; NSCLC; non-small cell lung cancer; RLL, right
lower lobe.
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497
The PET-CT scan was interpreted with all
available clinical information. In general, scans
were interpreted by either a board-certified
nuclear radiologist (DS) or nuclear medicine
physician (RH). A focus was considered positive
if activity was significantly above expected background and could not be explained by a normal
structure. The post-PET TNM stage was determined by the PET-CT fusion findings. The postPET TNM stage was compared with the TNM
stage based on clinical examination and diagnostic CT scan, MRI, and chest X-ray. Findings
suspicious for the presence of distant metastasis
or second primary cancers were confirmed either
histologically or by the combination of additional
imaging tests and clinical follow-up. The gross
tumor volume (GTV) using the PET-CT and CT
were contoured; based on the GTV, corresponding
clinical target volume (CTV), and planning target
volume (PTV) for both PET-CT and CT were derived and compared with each other. For contours
involving the PET-CT, the 50% intensity level
relative to tumor maximum was used to delineate
the borders of the GTV.
RESULTS
The impact of PET-CT on TNM score, AJCC
stage, and overall patient management was
analyzed. Overall, PET-CT altered the TNM score
in 13 patients (36.1%) and the AJCC stage in five
patients (13.9%). The changes in tumor status
and nodal status frequently did not have an
impact on overall stage but did have a significant
impact on radiation volume covered and dose
given. In some patients found to have distant
metastasis, and hence a change in the metastasis
score, the use of chemotherapy also changed.
Overall, PET-CT changed the management of
nine patients (25%).
Among the 36 patients who were initially seen with head and neck
cancer and underwent PET-CT for staging and
RT planning, four patients had their tumor score
increase, whereas none had their tumor score
decrease (Table 2). For nodal disease, three
patients had their nodal score increase, whereas
four patients had their score decrease after PETCT (Table 3). The AJCC stage was altered by
PET-CT in five (14%) of 36 patients; in four
patients, the AJCC stage increased, whereas in
one it decreased (Table 4). Three patients were
found to have distant metastasis, and their
disease was upstaged to stage IVC (Table 5).
One patient had a supraglottic laryngeal cancer
with extension to the esophagus in addition to
bilateral neck adenopathy, axillary, and mediastinal adenopathy (Table 5, patient 5). Another
patient had a soft palate carcinoma with bilateral
neck adenopathy and multiple right lung nodules
(Table 5, patient 7). In both patients 5 and 7,
pathologic confirmation of metastatic disease was
not done because of clinical presentation of widespread dissemination of disease. Another patient
had a hypopharyngeal cancer with bilateral neck
metastasis and a left lower lobe lung mass.
Biopsy of this lung lesion showed similar histologic features to the primary cancer and was
consistent with a metastasis (Table 5, patient 8).
Nine patients
(25%) had a change in management because of
the PET-CT. Table 5 lists the management
changes because of PET-CT.
Impact of PET-CT on Management.
Five patients had a change in RT
volume, and four had a change in RT dose
(patients 2 – 5). Changes in RT volume were
secondary to more extensive disease requiring a
larger volume to irradiate (patients 1 and 4),
discovery of the primary site in two patients with
Radiotherapy.
Impact of PET-CT on Staging.
498
FIGURE 1. PET component of PET-CT scan shows the primary
tumor in the larynx (a), contralateral neck disease (b), and upper
mediastinal node (c). This patient was treated to the primary site
only with palliative radiotherapy using a lower dose.
PET-CT Fusion in Radiotherapy Treatment Planning for Head and Neck Cancer
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June 2005
FIGURE 2. PET-CT image of a patient with squamous cell carcinoma of the posterior pharyngeal wall. CT image is shown on the left, and
PET image is shown on right. Arrows point to the primary tumor.
cervical metastasis from an unknown primary
tumor, eliminating the need to treat the nasopharyngeal area (patients 2 and 3), and discovery
of widespread distant metastasis, which required
only the symptomatic area to be irradiated (patient 5). Three patients had an increase, whereas
one had a decrease in RT dose because of PETCT. Both patients who had their primary sites
discovered after PET-CT received a higher dose to
the oropharyngeal primary tumor (patients 2 and
3). One patient was discovered to have contralateral neck disease requiring a higher dose to the
right side of the neck (patient 4). Another was
treated only to 3000 cGy as palliative treatment
to a symptomatic laryngeal tumor with esophageal extension and distant metastasis (patient 5,
Figure 1). In the four patients in whom PET-CT
downstaged nodal status, both radiation volumes
and dose were not changed on the basis of PETCT findings. Borderline adenopathy, as identified
on CT alone, was still treated on the assumption
that node-positive disease was present and was
included as part of the high-dose target volume.
Three patients had a change
in chemotherapy management. A decision not
to give chemotherapy was made in a patient
whose disease was downstaged after PET-CT
from T2N1M0 cancer of the tonsil to T2N0M0.
This patient had a 1.5-cm lymph node that was
positive on CT but negative on PET-CT; he received radiation alone, with the RT dose and
volume remaining unchanged (patient 6). In two
patients, a change in chemotherapy regimens was
made because of discovery of distant metastasis. One patient with a soft palate primary tumor
Chemotherapy.
FIGURE 3. Images of the same patient as in Figure 2, showing lung metastasis in left upper lobe of lung. CT image is shown on the left,
and PET image is shown on the right. Arrows point to site of distant metastasis. Biopsy of this lesion was consistent with a head and neck
primary tumor. This patient was treated with a different chemotherapy regimen because of this finding.
PET-CT Fusion in Radiotherapy Treatment Planning for Head and Neck Cancer
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499
was treated with cisplatin during RT and because
of distant spread was given post-RT chemotherapy consisting of paclitaxel and gemcitabine (patient 7). Another patient with a hypopharyngeal
primary tumor had his chemotherapy changed
from cisplatin to carboplatin and docetaxel because of pulmonary metastasis (patient 8, Figures 2 and 3).
One patient underwent a right lower
lobe lobectomy and mediastinal node sampling
after chemoradiation for a posterior pharyngeal
wall cancer, because the PET-CT revealed a 2-cm
cavitating mass with a standardized uptake value
of 8.5. Pathologic examination of the specimen
from lobectomy revealed an adenocarcinoma with
mediastinal node spread. His disease was then
staged as a T4N2M0 or stage IIIB NSCLC, and
he is currently awaiting adjuvant treatment (patient 9).
Surgery.
DISCUSSION
This single-institution study confirms previous
results showing that PET is able to identify the
primary lesion and regional lymph node involvement in patients with head and neck cancer.1 – 7
The increased sensitivity and specificity of PET in
the nodal staging of head and neck cancer has
been well documented, and the anatomic information added by combined PET-CT can lead to
even greater accuracy in the staging process. A
number of studies have evinced a clear role for
PET-CT fusion in the management and RT
planning of NSCLC.11 – 16 Less data are available
regarding the role of PET-CT fusion in patients
with head and neck cancer. In two recent studies
of patients with head and neck cancer, PET-CT
fusion was found to have an impact on RT target
delineation.22,23 In a study of 21 patients with nasopharyngeal or oropharyngeal primary tumors,
Nishioka et al22 found that PET-CT detected
39 positive nodes in contrast to only 28 nodes
detected by clinical examination and CT/MRI. In
four patients, the nodal status was increased,
which impacted on target delineation. Parotid
sparing became possible in 71% of patients whose
upper neck areas near the parotid glands were
tumor free by PET-CT, and, except for one
patient, no recurrences were seen at 18 months
when the PET-CT – defined volumes were used as
the GTV.22 Daisne et al23 reviewed 10 patients
with locally advanced oropharyngeal cancers who
had MRI and PET coregistration with CT simu-
500
lation images. They found that the average GTV
was 37% larger when MRI and PET were coregistered with CT compared with CT alone.
In this study, we found that the role of PETCT in staging has important ramifications for
clinical management, particularly with respect to
radiation dose given, radiation target volumes
covered, and the decision to give chemotherapy.
PET-CT fusion altered the TNM score in 38% and
AJCC stage in 14% of patients. The primary
tumor was identified in 33 (92%) of the patients
in this study, and the three patients in whom
tumor was not identified had a diagnosis of carcinoma of unknown primary tumor. In regional
lymph node involvement, PET-CT increased the
nodal score of three patients and decreased the
nodal score in four patients. Physiologic uptake in
normal organs in the head and neck such as the
cricoarytenoid muscles, salivary glands, tongue,
and tonsils can make interpretation of PET data
difficult, despite the fact that such uptake is
symmetric and can usually be distinguished from
cancer.20,21,24,25 With the recent advent of combined PET-CT, interpretation of PET becomes
less difficult and anatomic delineation becomes
more precise.
Certainly, there are limitations in this study.
First, the quality of image fusion between CT and
PET-CT images was evaluated subjectively by use
of three anatomic reference points in the head
and neck for the registration process. An error of
5 mm between the fused images was the upper
limit for what was considered an acceptable
registration, and a discrepancy of 2 to 3 mm was
the standard for most of the fused images. This
may have a slight impact on determination of
GTV on the basis of PET-CT.
Second, we did not have histologic confirmation of borderline lymph nodes, because most of
our patients with locally advanced disease underwent chemoradiation. In some patients, lymph
nodes that did not meet size criteria for disease on
CT exhibited increased FDG uptake on fused
images, and in others, lymph nodes that appeared
enlarged on CT failed to have any FDG uptake on
PET-CT. When PET-CT findings were not in
accord with CT findings for nodal detection, this
had a direct impact on prophylactic radiation
doses to the neck and what was considered as
GTV. Patients who had a positive neck node on
PET-CT but not on CT alone had change in RT
volume and dose to take into account the PET-CT
‘‘gross disease’’ instead of the CT ‘‘subclinical
disease.’’ The reverse, however, was not true. We
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June 2005
did not change our RT volumes and doses when
there was CT-positive lymphadenopathy that was
negative on PET-CT. Furthermore, for two of the
three patients with metastatic disease detected
by PET-CT, pathologic confirmation was not
obtained, and there is a possibility that they
had a synchronous cancer rather than distant
metastasis. However, this seems unlikely, because the two patients with unbiopsied distant
tumors had widespread disease.
Third, we acknowledge that the consistency of
target delineation with PET by visual determination and not by standardized uptake value can
be subjective, and this is why we rely on our
nuclear medicine colleagues to tell us the areas of
abnormality. Other potential problems with PETCT fusion that must always be considered include
patient movement during the combined PET-CT
and patient position being different between the
CT simulation and the PET-CT.
Fourth, we found that three patients had a
change in chemotherapy management, with two
having a change from cisplatin to another type of
regimen. Although cisplatin and RT are used in
our institution for curative therapy for many
locally advanced head and neck cancers, this may
not be the standard chemotherapy in other
centers. It may be that the chemotherapy regimens used for metastatic disease (paclitaxel/
gemcitabine and carboplatin/docetaxel) in our
institution are used in others as first-line chemotherapy for curative disease. Furthermore, one
may argue that a patient with T2N1 tonsillar
cancer could be treated with RT alone and not
chemoradiation as done in our institution. Hence,
the number of patients with change in management may have been overestimated and may only
be six of 36 patients or 16.7%.
Finally, one may speculate that a CT scan of
the chest would have detected the synchronous
lung primary tumor and two cases of metastatic
disease to the lungs. We do not know whether this
would be the case, because in our institution, it is
not routine to order a CT scan of the chest unless
there is an abnormality on chest X-ray. Data for
lung cancer, however, demonstrate the superiority of PET-CT over CT scan alone in detecting
lung disease.17
In our study, two of the five patients with
carcinoma of an unknown primary tumor had
primary disease confirmed by PET-CT findings.
In a review of all reported series on PET and
carcinoma of an unknown primary tumor, approximately 25% of primary tumors were detected
by PET imaging.26 Patients with head and neck
cancers are at a 4% per year risk of another
second primary cancer of the upper aerodigestive
tract developing, and second primary cancers are
a leading cause of death in this population. PET
has been shown to significantly increase the rate
of detection of simultaneous second primary
tumors, usually at an early stage, and distant
metastasis.27 – 29
In addition to PET, data from PET-CT has
been shown to have a significant impact on
staging and treatment planning in patients with
NSCLC. 11 – 18 The use of PET-CT data has
changed radiation management from 26% to
100% of patients with NSCLC compared with
CT-based treatment planning.10 In addition, the
use of PET-CT in patients with NSCLC has
resulted in more accurate staging, improved
sparing of normal lung tissue in radiation planning, and a more consistent definition of what
constitutes the GTV.14,17,30 This study found that
PET-CT has a significant impact on the staging
and clinical management of patients with head
and neck cancer. In the future, the use of PET-CT
in patients with head and neck cancer has the
potential to result in more accurate staging and
more precise target volume delineation and
consequent radiotherapy volumes and doses.
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