Metabolic Imaging of Malignant Pleural Mesothelioma With Fluorodeoxyglucose Positron Emission Tomography: Lymph node

Metabolic Imaging of Malignant Pleural Mesothelioma With Fluorodeoxyglucose Positron Emission Tomography: Lymph nodeLymph node involvement was detected by FDG-PET imaging in 12 patients as distinct sites of hypermetabolic lesions in the mediastinum, but biopsy specimen confirmation was available only in 6 (Table 2). Of these six subjects, lymph node metastases were confirmed in five, and granulomatous disease was diagnosed in one. One subject had distant metastasis in the thoracic spine demonstrated solely on PET, but this finding was not confirmed by biopsy specimen or other diagnostic studies. The FDG-PET scans showed no lymph node involvement in the remaining 12 patients with malignant disease. Canadian healthcare mall review Pathologic examination confirmed the absence of lymph node metastases in three, and in eight patients, lymph nodes appeared normal in size on CT scanning. One patient with normal FDG-PET imaging in the mediastinum developed metastases proven by thoracotomy 3 months after the scan. This patient had a biphasic mesothelioma. A CT scan obtained at the same time as the FDG-PET study did not reveal the presence of enlarged lymph nodes.
However, a repeat CT obtained just before surgery demonstrated lymph node enlargement. In the subjects in whom surgical staging was established (n=10), the sensitivity and specificity of FDG-PET imaging were 83% and 75%, respectively.
The results of the semiquantitative measurements in 26 subjects, 22 with malignant and 4 with benign diseases, are summarized in Table 3. There was a clear difference between the average SUV values as well as the average tumor-to-normal lung ratio of malignant and benign pleural diseases (p<0.0001). The analysis revealed that a SUV >2.0 can distinguish between malignant and benign diseases of the pleura. Using this criterion alone, 24 of 26 subjects (in whom quantitative information is available) would be accurately categorized as having benign or malignant disease, with a sensitivity of 91%, a specificity of 100%, and an overall accuracy of 92%. However, SUV values in some mesothelioma cases were very close to this threshold. This indicates that there is an obvious potential for some overlap between mesotheliomas with low FDG uptake and severe pleural inflammation based on the metabolic activity of the lesions alone. Among the patients with malignant pleural disease, the subtype of mesothelioma could be identified from the pathology report in 18 subjects. In the other subjects, either the subtype was not clearly mentioned, or a final diagnosis of adenocarcinoma was established. Mesotheliomas of the epithelial subtype (SUV=3.78±1.96; n=9) tended to have lower level of FDG uptake than those of mixed or sarcomatoid subtypes (SUV=6.16±3.46; n=9), but the difference was not statistically significant (p=0.095).
Table 2—FDG-PET in Staging Nodal Metastasis

Sta ging
•    FDG-PET positive for lymph node metastasis in 12/24 patients with malignant disease–    5 confirmed surgically (CT normal in 2/5)–    6 unconfirmed (110 pathologic lymph node staging; CT normal in 6/6) ‘

–    1 false positive (granulomatous lymphadenitis); CT normal

•    FDG-PET was negative in 12/24 patients with malignant disease

–    1 false negative (thoracotomy performed 3 months after the PET study; initial CT normal)

–    3 true negative (CT normal in 2/3)

–    8 unconfirmed (no surgical lymph node staging; CT normal in 8/8) “

•    FDG-PET was negative in 4/4 cases with benign disease

Results in Patients With Surgical Nodal Staging
Lymph Node Status
PET Malignant Benign Total
+ 5 1 6
1 3 4
Total 6 4 10

Table 3—Quantitative Analysis (26 Subjects)

Differentiation of Benign From Malignant Disease
Benign (n=4) (Value ±SD) Malignant (n—22) (Value ±SD) Normal Lung (Value ±SD)
SUVTumor/lung ratio 1.41±0.63*2.69±1.31f 4.91±2.90*12.97±9.23f 0.43±0.12
*p—0.000042. fp^0.000046.
Comparison Between Mesothelioma Subtypes
Epithelial Subtype (n—9) (Value ±SD) Biphasic/Sarcomatoid (n=9) (Value ±SD)
SUV 3.78±1.96| 6.16±3.46|
|p=0.095.

Category: Pulmonary Function

Tags: FDG, malignant mesothelioma, metabolic imaging, positron emission tomography