Value-Of-Contrast-Ct-In-Combination-With-Pet-Ct-In-Mesothelioma-Staging-Optimal-Protocol-For-Initial-Assessment.pdf

The Egyptian Journal of Radiology and Nuclear Medicine xxx (2016) xxx–xxx

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Original Article

Value of contrast CT in combination with PET/CT in mesothelioma
staging: Optimal protocol for initial assessment
Mohamed Houseni a,⇑, Amr Osama b, Dalia Ibrahim Mohamed b, Shahinda Salem c
a

Department of Diagnostic and Interventional Medical Imaging, National Liver Institute, Menoufia University, Shibin El-Koum, Egypt
Radiology Department, Faculty of Medicine, Cairo University, Cairo, Egypt
c
Nuclear Medicine Unit, Department of Clinical Oncology and Nuclear Medicine, Faculty of Medicine, Cairo University, Cairo, Egypt
b

a r t i c l e

i n f o

Article history:
Received 2 October 2016
Accepted 16 December 2016
Available online xxxx
Keywords:
Mesothelioma staging
18F-FDG-PET

PET/CT
Contrast CT

a b s t r a c t
Purpose: To assess the value of contrast enhanced CT (ceCT) when added to positron emission tomography combined with the standard low-dose non-contrast CT (PET/CT) protocols for staging patients with
malignant pleural mesothelioma (MPM).
Methods: Retrospective analysis of 47 patients with pathologically proved MPM. All patients underwent
PET/CT with low dose CT followed by ceCT. PET/CT and ce-CT were evaluated separately then in combination. All the results were validated either by histopathology and/or clinical-radiological follow-up.
Staging was performed based on TNM system.
Results: For T-stage, the sensitivities for PET/CT, ceCT and combined PET/CT-ceCT were 89.1%, 86.9%, and
97.5%, respectively, p = 0.04. Regarding nodal stage, the sensitivity, specificity and accuracy for PET/CT
were 88.5%, 90.5%, and 89.4%; for ceCT 73.1%, 95.2% and 82.9%; and for PET/CT-ceCT 96.2%, 95.2% and
95.7%, respectively. PET/CT-ceCT significantly associated with the sensitivity, p = 0.05. Considering the
metastatic disease, the sensitivity, specificity and accuracy for PET/CT were 81.3%, 96.8%, and 91.5%;
for ceCT 56.3%, 90.3% and 78.7%; and for PET/CT-ceCT 93.8%, 96.8% and 95.7%, respectively. PET/CTceCT significantly improved the sensitivity (p = 0.03) and accuracy (p = 0.02). Furthermore, combined
PET/CT-ceCT significantly identified patients not suitable for surgery.
Conclusion: The addition of ceCT to PET/CT protocol has significantly contributed to the staging of MPM.
Ó 2016 The Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier. This
is an open access article under the CC BY-NC-ND license ( />4.0/).

1. Introduction
Malignant pleural mesothelioma is an aggressive cancer. It
mainly affects the parietal pleura and may invade local structures.
Treatment may involve a combination of radical surgery,
chemotherapy and radiation [1]. Accurate staging of mesothelioma
is paramount to choose the most efficient treatment strategy. The
most significant step in staging and re-staging is to identify
patients who may get benefit from surgery [2]. Based on The European Organization for Research and Treatment of Cancer (EORTC),
patients with T4, N2-N3 nodal stage as well as M1 metastatic status are precluded from surgery [3].
The role of PET/CT in oncology is well established. It has changed the diagnostic algorithm in cancer patients [4–6]. In mesothe-

Peer review under responsibility of The Egyptian Society of Radiology and Nuclear
Medicine.
⇑ Corresponding author.
E-mail address: (M. Houseni).

lioma, PET/CT is a powerful modality in the depiction of
mediastinal as well as chest wall invasion [7]. It is also superior
to other modalities in the detection of lymphadenopathy and
metastatic disease [8]. On the other hand, exact local tumor
extension and the assessment of small lesions are challenging with
PET/CT [9].
Contrast CT chest is widely used to evaluate pleural mesothelioma. It defines primary tumor outline, local invasion, intrathoracic lymphadenopathy and extra-thoracic extension [8]. This
is because of the superb soft tissue resolution and the availability
of multi-planar image reconstruction from the volumetric acquisition [10]. However, CT is limited when assessing normal sized
lymph nodes. In addition, CT suffers from reduced sensitivity in
the detection of metastatic lesions that are not associated with
structural changes [11].
It is still recommended to perform attenuation correction for
PET using low dose non-contrast CT to avoid beam-hardening artifacts from contrast. Furthermore, metabolic activity may falsely
increased as a result of contrast [12]. An added issue in the thorax

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is respiratory motion artifact, which affects the spatial resolution
of PET images and the accuracy of the attenuation correction information [13]. Therefore, the acquisition of PET and low dose CT in
quite respiration will limit this artifact; then performing contrast
CT with breath-hold will provide superior chest images.
The purpose of this study was to assess the value of contrast
enhanced CT (ceCT) when added to positron emission tomography
combined with the standard low-dose non-contrast CT (PET/CT)
protocols for staging patients with malignant pleural mesothelioma (MPM).

collimation for detector configuration. The gantry rotation time
was 0.5 s, field of view of 50 cm and reconstruction matrix of
512  512. Automated exposure control was applied for all
patients (CARE Right, Siemens Medical Solutions, Forchheim, Germany) with 120 kV tube potential and the average mAs of 150.
Trans-axial images were reconstructed at 1.5 mm slice thickness
in 1 mm increment using a convolution kernel B20f body filter.
For multi-planar evaluation, coronal and sagittal images with a
1.5 mm slice thickness in 1 mm increment were reconstructed.
2.3. Image interpretation

2. Methods
2.1. Patients
This retrospective study included adult patients referred for initial assessment of pathologically proven pleural mesothelioma.
This study was approved by the institutional review board. The
need for informed consent was waved.
Forty-seven consecutive patients were included during the period between November 2012 and February 2016.
All patients have performed 18F-FDG-PET/CT with low dose CT
followed by diagnostic contrast enhanced CT as part of the imaging
protocol.
2.2. Imaging protocol

All patients underwent 18F-FDG PET/CT examinations using a
dedicated PET/CT scanner equipped with a 20-slice CT system (Siemens mCT20, Biograph Classic; Siemens Medical Solutions, Knoxville, USA). Patients fasted for about 6 h before the injection time.
Serum glucose levels were measured before injection to confirm
euglycemia (blood glucose level <200 mg/dL). Then, 370–
550 MBq of 18F-FDG was injected with a saline infusion in the
antecubital vein depending on the weight. Patients were asked to
drink 750 mL of 5% mannitol as a negative oral contrast during
the uptake phase. Approximately after 60 min from injection,
PET/CT scans were performed. Scanning was performed in a supine
position with patient’s arms rested above head.
A low-dose CT scan, for attenuation correction and anatomical
mapping. The acquisition was performed in helical mode from
skull base to mid-thigh, using 150 kV, 50 mAs, and a 512  512
matrix size, acquiring a field of view (FOV) of 780 mm in about
20 s.
The emission PET scan was acquired, after the low dose CT, in a
three-dimensional mode (3D) from skull base to mid-thigh. Imaging was performed, using sequential overlapping bed positions
with the acquisition time of three minutes per bed position. The
number of bed positions depends on the patient’s height with
one-slice overlap at the borders of the FOV. Dead-time correction
and online delayed coincidence subtraction were used to correct
for random coincidences. The low-dose CT images were rescaled
to produce attenuation correction values for the PET scan. Image
reconstruction based on point-spread function (PSF) together
with time of flight (TOF) (Siemens ‘ultraHD
PET’; iterations, 2; subsets, 21). The projection data were reconstructed by 3-mm slice
thickness. Gaussian filter (FWHM, 2 mm) was used for the reconstructed data. Finally, the low dose CT was reconstructed using a
convolution kernel B20f body filter.
Following PET imaging, volumetric contrast enhanced CT scanning was performed from skull base to mid-thigh on the same PET/
CT machine using the helical 20-slice multi-detector CT system of
the PET/CT scanner. Intra-venous contrast was given at a rate of

1.5 ml/kg with overall dose ranging from 80 to 100 ml. The CT
acquisitions were performed using a 1.2-pitch and 20  0.6 mm

PET/CT studies were reviewed separately by a consultant
nuclear medicine. Contrast enhanced CT images were reviewed
independently by a consultant radiologist. After that the combined
PET/CT-ceCT images were evaluated in consensus by both
consultants.
2.3.1. PET images interpretation
All the images were reviewed to assess the primary site, lymph
nodes and metastatic disease. Lesions with increased 18F-FDG
uptake in comparison to the surrounding background were considered malignant.
2.3.2. Contrast CT images interpretation
Regarding the primary site, nodular pleural lesion, thickening
greater than one cm or abnormal pleural enhancement were considered malignant. Lymph nodes larger than one cm in short axis,
enhancing, necrotic or rounded nodes were considered positive.
Abnormal focal lesions that do not demonstrate known benign features by diagnostic CT were considered distant metastases.
2.4. Staging
Staging was done on a patient basis, in accordance to the seventh edition of the AJCC cancer staging manual [14]. The nodal
and metastatic lesions were verified based on histopathology
and/or the clinic-radiologic follow-up.
2.5. Statistics
Sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and prevalence were computed from the
resulting 2  2 contingency tables. The chi-square test was used
categorical data. A p-value < 0.05 was considered statistically significant. All tests performed by using IBM SPSS Statistics, version
20, (IBM Corp, Armonk, NY).
3. Results
3.1. Patients
Forty-seven patients (39 men and 8 women) with mean age 55year (range between 22 and 70 years), with pathologically proved
mesothelioma were retrospectively evaluated. Mean blood glucose

was 117.5 mL ± 21 at the time of 18F-FDG injection. All the findings for local tumor spread, nodal status and distant metastases
have been confirmed with histopathology and/or clinicalradiological follow-up. The average follow-up period was
17.8 months (range, 6–38 months).
3.2. Primary tumor stage
For T-staging, 7 patients were T1, 12 cases demonstrate T2, 17
with T3 and 11 patients were T4. 18F-FDG-PET/CT correctly

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M. Houseni et al. / The Egyptian Journal of Radiology and Nuclear Medicine xxx (2016) xxx–xxx
Table 1
Overall results for 18F-FDG-PET/CT, contrast CT and combined PET/CT with contrast
CT regarding lymph nodal staging.

Sensitivity
Specificity
Accuracy
Positive
predictive value
Negative
predictive value
*

18F-FDGPET/CT (%)

Contrast CT
(%)

PET/CT-ceCT

(%)

p
value

88.5
90.5
89.4
92

73.1
95.2
82.9
95

96.2
95.2
95.7
96.2

0.05*
0.7
0.1
0.8

86.4

70.1

95.2

0.1

3

classified 41 of the cases; one case was falsely overstaged and five
were falsely understaged. The sensitivity for 18F-FDG-PET was
89.1% with positive predictive value (PPV) 97.6%. Contrast CT correctly classified 40 of the patients; one case was falsely overstaged and six were falsely understaged. The sensitivity for
contrast CT was 86.9% with positive predictive value 97.5%. When
the data from 18F-FDG-PET/CT and contrast enhanced CT (PET/
CT-ceCT) combined together there was overstaging in one patient
with no understaging in any case. The sensitivity of T-stage is significantly associated with the use of combined PET/CT-ceCT, p
value 0.04.

p value is significant.

Comparison chart between PET, PET/CT and PET/CT-ceCT
regarding Nodal Stage
100.0%
90.0%
80.0%
70.0%
60.0%

PET

50.0%

ceCT

40.0%

PET/CT-ceCT

30.0%
20.0%
10.0%
0.0%
Sensitivity Specificity

Accuracy

PPV

NPV

Fig. 1. Comparison chart for the sensitivity, specificity, accuracy, PPV and NPV between PET, PET/CT and PET/CT-ceCT regarding nodal stage.

Fig. 2. A patient with locally advanced metastatic malignant pleural mesothelioma. (A) Coronal fused PET/CT image demonstrates chest wall (red arrow), transdiaphragmatic (white arrow) and mediastinal invasion (green arrow). Also noted, bilateral adrenal (white arrow heads) and bone marrow (red arrow head) deposits. (B)
Trans-axial fused PET/CT shows bilateral metastatic cervical lymphadenopathy (white squares). (C) Trans-axial PET/CT image exhibits liver deposit (red circle).

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Table 2
Overall results for 18F-FDG-PET/CT, contrast CT and combined PET/CT with contrast

CT regarding metastatic disease.

Sensitivity
Specificity
Accuracy
Positive
predictive value
Negative
predictive value
*

18F-FDGPET/CT (%)

Contrast CT
(%)

PET/CTceCT (%)

p
value

81.3
96.8
91.5
92.9

56.3
90.3
78.7
75

93.8
96.8
95.7
93.8

0.03*
0.4
0.02*
0.4

90.9

80

96.8

0.05*

p value is significant.

3.3. Lymph nodal involvement
Regarding lymph nodal state, 26 patients had metastatic lymph
nodes and 21 cases were N0. 18F-FDG-PET/CT correctly classified
42 of the cases; two cases were falsely overstaged and three were
falsely understaged. Contrast CT correctly classified 39 of the
patients; one case was falsely overstaged and seven were falsely
understaged. Combined PET/CT-ceCT correctly diagnosed 45 cases;
one case was falsely overstaged and one case falsely understaged.
The sensitivity, specificity, PPV, negative predictive value (NPV)

and accuracy for 18F-FDG-PET/CT, contrast CT and PET/CT-ceCT
regarding nodal stage are shown in Table 1 and as a comparative
chart in Fig. 1. The sensitivity of lymph nodal detection is significantly associated with the use of combined PET/CT-ceCT.
3.4. Metastatic disease
Distant metastases were confirmed in 16 patients. Eleven of the
patients had multiple organs involvement. Metastatic disease
involved lungs (n = 7), distant lymph nodes (n = 3), bone marrow
(n = 6), adrenal glands (n = 3), peritoneal (n = 2) and liver (n = 4).
An example is of metastatic disease is presented in Fig. 2. 18FFDG-PET/CT correctly classified 12 of the cases; one case was falsely overstaged and three were falsely understaged. Contrast CT
correctly classified six of the patients; three cases were falsely
overstaged and seven were falsely understaged. Combined PET/
CT-ceCT correctly diagnosed 14 cases; one case was falsely overstaged and one case falsely understaged. The sensitivity, specificity,
PPV, NPV and accuracy for 18F-FDG-PET/CT, contrast CT and PET/

CT-ceCT regarding distant metastases are shown in Table 2 and
as a comparative chart in Fig. 3. Using combined PET/CT-ceCT is
significantly associated with the sensitivity, accuracy and NPV for
the assessment of distant metastasis.
3.5. Overall TNM staging
Detailed TNM staging is shown in Table 3. Surgery was not suitable in 22 patients, 18F-FDG-PET/CT detected 20 cases, contrast CT
identified only 14 cases, whereas, combined PET/CT-ceCT revealed
21 patients. Unnecessary surgery was avoided in 10 patients with
PET/CT-ceCT by diagnosing four patients with T4 stage and detecting metastatic disease in another six cases. Combined PET/CT-ceCT
is significantly associated with the identification of patients not
suitable for surgery, p value 0.01. Analysis of the disease stage
demonstrated that 18F-FDG-PET/CT incorrectly staged 8 patients,
contrast CT incorrectly staged 14 cases and PET/CTceCT incorrectly
staged 5 patients, p value of 0.05.
4. Discussion
Malignant pleural mesothelioma is an aggressive cancer. It

affects the pleura and may invade local structures. Accurate staging of mesothelioma is critical to choose the suitable treatment
strategy. In addition, staging directly affects the management and
prognosis. Multi-modality imaging approach can significantly
improves staging of cancer and continuous efforts are being made
to adjust imaging protocols to get the most informative data for
tumor staging [15].
In this study, using combined PET/CT-ceCT has significantly
improved the sensitivity of primary tumor T-stage, p value 0.04.
The sensitivity of PET/CT and CT for local tumor extent was almost
equal and tends to underestimate the T-stage. This is in agreement
with other published data [16] and slightly lower than a study
published by Abe et al. [17]. Currently, there are limited data considering the clinical value of PET/CT-ceCT in pleural mesothelioma.
Schaarschmidt et al. [18] reported that PET/CT and PET/MRI can be
used for pleural mesothelioma staging in a study included only six
patients. 18F-FDG-PET combined with low dose CT could be of limited value in outlining the local tumor extent [8]. Furthermore,
PET/CT alone may not give precise information about the T-stage
because of the non-contrast CT images [19]. A recent study showed
that the use of volumetric CT may contribute to the clinical T-stage

Comparison chart between PET, PET/CT and PET/CT-ceCT
regarding Metastatic status
100.0%
90.0%
80.0%
70.0%
60.0%

PET

50.0%

ceCT

40.0%

PET/CT-ceCT

30.0%
20.0%
10.0%
0.0%
Sensitivity Specificity

Accuracy

PPV

NPV

Fig. 3. Comparison chart for the sensitivity, specificity, accuracy, PPV and NPV between PET, PET/CT and PET/CT-ceCT regarding metastatic status.

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M. Houseni et al. / The Egyptian Journal of Radiology and Nuclear Medicine xxx (2016) xxx–xxx
Table 3
Stages of mesothelioma.
Clinico-pathological Staging

T

N

M

PET/CT
No.

Stage I
T1

N0

M0

7

Stage II
T2

N0

M0

8

Stage III
T2
T3

T3
T3

N1
N0
N1
N2

M0
M0
M0
M0

2
4
4
2

8
12

Stage IV
T2

T
7

20
N0

M1

2

T3
T3
T3
T4

N1
N2
N3
N1

M1
M1
M1
M0

3
3
1
4

T4

N2

M1

3

T4

N3

M1

4

Contrast CT
N

M

No.

Stage I
T1

N0

M0

6

Stage II
T2

N0

M0

10

Stage III
T2
T3
T3
T3

N1
N0
N1
N2

M0
M0
M0
M0

2
5
5
1

10
13

Stage IV

T2
T2
T3
T3
T3
T4
T4
T4
T4
T4

T
6

18
N0
N1
N1
N2
N3
N1
N2
N2
N3
N3

M1
M1
M1
M1

M1
M0
M0
M1
M0
M1

1
1
1
6
1
2
1
1
1
3

PET/CT-ceCT
N

M

No.

Stage I
T1

5
N0

M0

5

Stage II
T2

N0

M0

12

12

Stage III

15

T3
T3
T3

N0
N1
N2

M0
M0

M0

6
5
4

Stage IV
T1

N0

M1

1

T3

N0

M1

3

T3
T3
T4

N2
N3
N1

M1
M1
M0

3
3
2

T4
T4
T4

N2
N3
N3

M1
M0
M1

1
1
1

14

T

N

M

No.

Stage I
T1

N0

M0

6

Stage II
T2

N0

M0

9

Stage III
T2
T3
T3
T3

N1

N0
N1
N2

M0
M0
M0
M0

1
4
6
1

6
9
12

Stage IV

20

T2

N0

M1

2

T3
T3
T3
T4

N1
N2
N3
N1

M1
M1
M1
M0

2
4
1
4

T4

N2

M1

3

T4

N3

M1

4

TNM staging according to The American Joint Committee on Cancer (AJCC) [14].

of malignant pleural mesothelioma [20]. Combining both the
metabolic information and the data from the high-resolution contrast CT in our study has significantly improved the local tumor
assessment. There was incorrect staging in six cases by PET/CT
alone and in seven cases by contrast CT alone. One case has been
overstaged by both modalities at the site of biopsy, which demonstrated focal increased 18F-FDG uptake with underlying contrast
enhancement. These findings have been resolved on follow-up
and attributed to post interventional inflammatory changes. It
has been reported that inflammatory reaction at the interventional
site can cause false positive results on CT [21] as well as on PET
images [22]. PET/CT understaged five cases, two with pericardial
and three with diaphragmatic involvement, an example is shown
in Fig. 4. It is known that the size and the shape of lesions affect
their detection on PET imaging. Roca et al. [23] indicated that small
and flat pleural lesions are less detectable on PET/CT. Contrast CT
understaged six cases with chest wall infiltration as shown in
Fig. 5. CT often underestimate T-stage due to difficult detection
of extra-pleura fat invasion [16,24]. In our study, using combined
PET/CT-ceCT has eliminated all the false negative results.
The overall prevalence of N2 or N3 disease was 55.3%. Combined PET/CT-ceCT has significantly improved the sensitivity of
detection of lymph nodal deposits, p value 0.05. The accuracy of
PET/CT was higher than CT alone in our analysis. Several studies
have reported similar data [16,25,26]. In this analysis, contrast

CT tends to understage mediastinal lymph nodes with false negative rate of about 15%, which occurred in the evaluation in normal
sized lymph nodes as reported by other studies [9,27]. A cutoff of
1 cm may be high and leads to underestimation of the involved
nodes [16]. PET/CT alone overstaged 4% and understaged 6% of
cases. False positive PET results found in reactive nodes, whereas,
false negative results occurred in small sized lymph nodes. It has
been reported that inflammatory changes in reactive nodes may
result in false positive findings on PET/CT [28,29], on the other
hand, small lesions can be falsely negative due to partial volume
effect [30]. Furthermore, the presence of hilar nodes in the vicinity
of primary tumor causes misinterpreted results [27,31]. Ambrosini
et al. [32] found that PET/CT identified more metastatic mediastinal lymph nodes than CT alone in patients with mesothelioma.

Fig. 4. (A) Trans-axial contrast CT demonstrates enhancing pleural nodule along the
left diaphragm (arrow) which is not 18F-FDG avid on the (B) fused PET/CT image.

Combined PET/CT-ceCT was falsely negative in one case with small
lymph node and false positive in one case with reactive lymph
node.

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Fig. 5. (A) Axial PET image, (B) contrast CT, and (C) combined PET/CT-ceCT demonstrating increased 18F-FDG uptake in the primary right pleural neoplasm (arrows) with
focal increased activity in the right serratus anterior muscle (arrow heads) which is not depicted on the contrast CT.

A

B

C

D

Fig. 6. Trans-axial images at initial staging; (A) fused PET/CT and (B) CT demonstrate non-FDG avid pulmonary nodule measures 7 mm (arrows). Follow-up images (C) fused
PET/CT and (D) CT after three months demonstrate size progression of the nodule to 10 mm with newly developed 18F-FDG uptake in the nodule. The follow-up study
revealed the metastatic nature of the nodule that was a false negative finding on the initial 18F-FDG-PET study.

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A

7

B

Fig. 7. (A) Trans-axial fused PET/CT image demonstrates 18F-FDG avid bone marrow deposit (arrow), which was false negative on the (B) CT image with no associated
morphologic or structural changes.

The prevalence of metastatic disease was 34%. Combined PET/
CT-ceCT has significantly improved the sensitivity (p value 0.03),
the accuracy (p value 0.02) and the negative predictive value (p
value 0.05). Although, it has been reported that PET/CT provides

a high detection rate in distant metastases [33], PET/CT overstaged
one case with reactive lymph node and underestimated three
cases. The false negative results with PET/CT occurred in a peritoneal deposit showing mild soft tissue thickening, another case
with small pulmonary nodules (Fig. 6) and a third case with small
lymph node. All the three false negative results demonstrate no
significant 18F-FDG activity. Li et al. [34] reported low specificity
for small lesions especially in pulmonary nodules. Similar data
have been reported by Aquino et al. [35] with high false negative
rate in small lung nodules. The evaluation of small pulmonary nodules is challenging with PET/CT because of the relative low spatial
resolution. On the other hand, contrast CT overstaged three cases
and understaged seven cases. The false positive rate was 9.7%
and occurred with small pulmonary nodules proved to be stable
on follow-up studies. The false negative rate for CT was 43.7%. It
has been found in four cases with bone marrow, as shown in
Fig. 7, and two with liver deposits. There were no definite CT
changes corresponding to the pathologic 18F-FDG uptake within
the liver or bone marrow deposits. The 7th false negative case
occurred in a normal size lymph node. We noticed that more than
half of the false negative cases with contrast CT observed in bone
marrow deposits. This has also been observed by other researchers
[36]. In another study, Bier et al. [37] showed a sensitivity of 36.8%
in the detection of bone marrow deposits for contrast CT with most
of the missed lesions located in the medulla. Regarding liver deposits, Odalovic et al. demonstrated lower sensitivity for CT (60%)
compared to PET (83%) in the detection of liver metastases. Similar
to the regional lymph nodal results, combined PET/CT-ceCT was
falsely negative in a small distant metastatic lymph node and falsely positive in a reactive node.
Overall, combined PET/CT-ceCT has changed the management
in 10 cases (21.3%) by hindering futile surgery because of T4 stage
or metastatic disease. Schneider et al. [26] reported the detection
of occult metastases in 2 of 18 patients with mesothelioma by

using PET/CT. On the other hand, Sorensen et al. [25] showed that
PET/CT has changed the management in 29% of mesothelioma
cases. His study included 42 patients. In addition, Erasmus et al.
[9] investigated 29 patients with mesothelioma and indicated that
11 cases (38%) avoided unnecessary surgery based on PET/CT data.
In a study included 100 patients with different malignant tumors,
the additional information by integrating contrast CT in the regular
PET/CT protocol has changed the management in 21% of cases. In
the same study, contrast CT provided additional valuable data in
52% of the cases [38]. It has been reported that mesothelioma

relapse after surgery may occur at the site of occult metastases.
Therefore, enhancing the detection of metastatic disease can help
the selection of patients for surgery and decrease the incidence
of early disease relapse [39].
There were some limitations in our study. The number of the
patients is relatively small; therefore it could slightly deviate from
the malignant mesothelioma population. However, as mesothelioma is a rare tumor, our study represents a suitable analysis. In
addition, we included only patients with pathologically proven
mesothelioma which might further limited the size of the study.
In conclusion, combined PET/CT-ceCT has significantly contributed positively to the staging of pleural mesothelioma. Our
analysis demonstrated potential benefit of 18F-FDG-PET by mapping active disease in addition to the power of diagnostic contrast
CT, which delineates the tumor in a precise way. PET/CT-ceCT can
overcome the weakness of both modalities when interpreted separately. Performing contrast CT as part of the PET/CT protocol has
the ability to provide considerable additional value for patients
with mesothelioma with significant improvement of the sensitivity
and accuracy. Furthermore, PET/CT-ceCT is significantly associated
with the identification of patients unsuitable for surgery.
Conflict of interest
The authors declare that they have no conflict of interest.

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