A 73-year-old woman presented with complaints of ongoing weight loss and
intermittent abdominal discomfort. CT of the chest, abdomen and pelvis revealed
a 4.3 cm × 3.8 cm spiculated left upper lobe mass and subcentimeter
bilateral nonspecific pulmonary nodules. There was no evidence of mediastinal
or hilar adenopathy. Imaging also revealed a 4.8 cm × 2.2 cm density in
anterior abdominal wall involving the musculature, large amount of ascites,
multiple omental masses. There was no evidence of bowel obstruction, but there
was a 4.6 cm × 4.2 cm mesenteric mass contiguous with the walls of
multiple small bowel loops, with infiltration of mesenteric fat. An FDG-PET/CT
confirmed the left upper lobe spiculated mass with an standardized uptake value
of 7, and several nonhypermetabolic subcentimeter bilateral lung nodules were
also noted. The omental and peritoneal masses had mild-to-moderate metabolic
activity with standardized uptake value between 1.7 and 3, and the mesenteric
mass had standardized uptake value of 2.5. The anterior abdominal wall mass had
standardized uptake value of 1.1.
The patient underwent left upper lobe resection revealing a 4.6 cm
mucinous, moderately differentiated adenocarcinoma, invading overlying pleura.
All lymph nodes were negative but lymphatic invasion was present. The
immunohistochemistry was positive for CK7 and TTF-1 and negative for CD20, CDX2
She recovered without complications and underwent laparoscopy and biopsy
of peritoneal mass, which was consistent with metastatic adenocarcinoma. On
pathologic evaluation, this biopsy differed morphologically from the lung
specimen, and was less columnar than the original.
Immunohistochemistry was strongly positive for CK7, calretinin, D240,
CK5/6, focally positive for WT1, negative for TTF-1, CK20, ER/PR breast 2 and
CA125. This pattern was most consistent with malignant mesothelioma.
Repeat FDG-PET/CT three months later revealed numerous bilateral
subpleural nonhypermetabolic nodules. The previously seen dominant mesenteric
mass had increased in size by almost 3 cm in length although standardized
uptake value was essentially unchanged, from 2.5 to 2.7. There was progression
of nodular thickening of the greater omentum, with standardized uptake value of
2.9, increased peritoneal implants and intra-abdominal and pelvic ascites.
Also, several new mildly hypermetabolic lesions were noted in the sternum,
thoracic vertebrae and iliac bones.
The patient began palliative chemotherapy with cisplatinum and
pemetrexed (Alimta, Eli Lilly), and tolerated the first two cycles without
Figure 1: Initial PET/CT examination demonstrates
hypermetabolic activity (yellow circle) associated with primary lung carcinoma.
Upper left image is axial CT scan, upper right image is corresponding PET
image, lower left image is fusion image containing PET images displayed on a
color scale and CT images displayed on a gray scale. Lower right image is
maximum intensity project (MIP) image of whole body PET study.
Figure 2: Initial PET/CT examination demonstrates
hypermetabolic activity (yellow circle) associated with omental implant.
Display convention is the same as Figure 1.
Figure 3: Comparison of initial and follow-up PET/CT
examination demonstrates increasing amount of ascites. Display convention is
the same as Figures 1 and 2.
Figure 4: Follow up PET/CT examination demonstrates
hypermetabolic activity associated with a new mixed/sclerotic lesion in the
sternum. Display convention is the same as Figures 1, 2 and 3.
Munir Ghesani, MD, is Associate Clinical Professor of Radiology at
Columbia University College of Physicians and Surgeons and Attending
Radiologist at St. Lukes-Roosevelt Hospital Center
Carrie Wasserman, MD, is a second year Hematology/Oncology Fellow at
St. Lukes-Roosevelt Hospital Center.
Anupama Goel, MD, is an Attending Physician in the Division of
Hematology & Oncology at St. Lukes Roosevelt Hospital Center.
Primary peritoneal mesothelioma shares the biologic and clinical
characteristics of pleural mesothelioma but is much less common, with an
incidence of about one in one million. Both are associated with a history of
asbestos exposure and tend to spread locally. They are often aggressive,
although some patients who undergo multimodality therapy for localized disease
do have prolonged survival. The median survival of patients with untreated
malignant mesothelioma is four to 13 months, or six to 18 months in treated
patients, with the majority dying from local chest extension and respiratory
Tumor extension below the diaphragm or primary peritoneal mesothelioma
may result in death from small bowel obstruction. For patients with advanced
(unresectable or recurrent) peritoneal disease, palliative systemic
chemotherapy is identical to that for pleural-based disease. Three randomized
trials have concluded that chemotherapy with a platinum-based doublet prolongs
survival compared to single-agent treatment or best supportive care.
The role of FDG-PET/CT for staging and follow-up of mesothelioma is
evolving. FDG-PET/CT appears to be quite sensitive for detecting extrathoracic
mesothelioma, but its sensitivity for determination of resectability and local
thoracic staging may be more limited.
One study evaluated the utility of FDG-PET in the preoperative
evaluation and staging of patients who were potential candidates for aggressive
combined modality therapy. In 18 patients with biopsy proven malignant
mesothelioma, the FDG-PET results were compared with results from staging
workup including CT scan, mediastinoscopy, thoracoscopy and pathologic
evaluation of biopsy specimens. All mesotheliomas were FDG-PET avid with a mean
standardized uptake value of 7.6 (range 3.33-14.85; n=9). The FDG-PET
evaluation did reveal occult extrathoracic metastases in two patients, which
excluded them from surgery. There were no false negative FDG-PET images, but
two false positives: one in the contralateral chest whose biopsy was negative
and another after partial colectomy.
In another series, 28 patients with suspected malignant pleural
mesothelioma were evaluated by FDG-PET imaging. Surgical biopsy confirmed the
presence of malignant disease in 24 of 28 patients and demonstrated benign
processes in the remaining four. The uptake of FDG was significantly higher in
malignant than in benign lesions. Using a standardized-uptake value cutoff of
2.0 had a sensitivity of 91% and a specificity of 100% for malignant disease.
Another retrospective series of 60 patients with biopsy-proven
malignant pleural mesothelioma were identified who had undergone FDG-PET
imaging preoperatively. The clinical stage based on FDG-PET was compared with
the surgical and pathologic results. The FDG-PET was positive in 59 of 60
patients, and the one false negative had only small volume pleural disease.
However, the sensitivity of FDG-PET in detecting T4 (unresectable) disease was
only 19%. The sensitivity for lymph node involvement was 11%.
The use of FDG-PET/CT in monitoring response to treatment has not been
well studied. The small number of patients and inherent difficulty evaluating
response to treatment in this disease has made phase-3 trials difficult to
conduct. Both the objective response rate (measured as a decrease of >30%
thickness of pleural rind perpendicular to rib on CT scan) and progression-free
survival have been used as surrogates for efficacy in all the phase-3 studies
to date. A decrease in hypermetabolism on FDG-PET may prove a better method to
follow response to treatment but this has not yet been validated.
FDG-PET/CT is a useful tool for evaluating patients in whom one has a
high index of suspicion for mesothelioma, especially those with distant
metastatic disease. It is likely to be useful in following response to systemic
treatment as well. It is less useful for staging and determination of
resectability because the relatively low metabolic activity and characteristic
pattern of spread of makes it difficult to differentiate malignant from benign
For more information:
- Schneider DB, et al. PET Positron emission tomography with
f18-fluorodeoxyglucose in the staging and preoperative evaluation of malignant
pleural mesothelioma. J Thorac Cardiovasc Surg. 2000;120:128-133.
- Benard F, et al. Metabolic imaging of malignant pleural
mesothelioma with fluorodeoxyglucose positron emission tomography.
- Flores RM, Akhurst T, Gonen M, et al. Positron emission tomography
defines metastatic disease but not locoregional disease in patients with
malignant pleural mesothelioma. J Thorac Cardiovasc Surg.