The staging for patients with malignant mesothelioma is carried out radiographically and/or surgically.
Imaging studies – These are commonly used for the evaluation of patients with suspected resectable malignant mesothelioma. Potential options available include CT, MRI, PET, and integrated PET/CT.
Chest CT – This is useful in identifying invasion of the ribs, chest wall and mediastinal structures. Potential indicators of tumor invasion include gross extension into mediastinal fat, loss of normal fat planes, and tumor which surrounds more than 50% of mediastinal structures. However, it has limited ability to accurately detect the involvement of intrathoracic lymph nodes.
MR imaging – For specific patients with suspected resectable disease, some physicians recommend Magnetic Resonance (MR) imaging in order to further examine the local extent of disease. In particular, coronal MRI may help identify the spread of pleural mesothelioma via the diaphragm into the peritoneal cavity.
PET scan – PET scans that make use of 18-fluorodeoxyglucose (FDG) have been helpful in detecting extrathoracic disease. However, in cases where only PET was used, a number of false negatives and false positives were reported during evaluation of mediastinal lymph nodes.
Integrated PET-CT – This type of imaging technique has proved most reliable for initial assessment of the patient. Below are three single institutional series that demonstrate the results obtained using the above technique:
- In the first series, 42 successive patients without any signs of T4 or M1 disease (based on CT) were evaluated using PET-CT. 12 patients (29%) were reclassified as terminal cases, based on the existence of a T4 lesion or distant metastasis (29% and 14% respectively).
- In the second series, 54 patients with suspected resectable mesothelioma (stage II/III) were evaluated using PET-CT. Surgical procedures were used to establish the imaging findings among 52 patients whereas two patients who had distant metastases were followed. It was noted that PET-CT was considerably more accurate than MRI, CT or PET alone for both stage II and stage III disease.
- In the third series, a comparison between PET-CT and CT in 35 patients was carried out. Based on the PET-CT findings, surgical resection was not indicated in 14 of the 35 cases (40%). This was usually due to the increase in the staging of the primary tumor.
Surgical staging – Extended surgical staging is recommended in cases where extrapleural pneumonectomy (EPP) is still being considered an option after imaging studies. In a series of 118 successive patients, surgical staging involved laparoscopy with peritoneal lavage in order to detect subdiaphragmatic involvement. This was followed by mediastinoscopy. This procedure helped avoid inappropriate interventions in 16 patients (14%).
Other studies – There are many other types of studies that can provide clinically useful ancillary information.
- Mediastinoscopy has shown to be increasingly effective in mesothelioma diagnosis and staging. This is based on recent studies that have shown considerable negative prognostic effects of mediastinal nodal invasion.
- Usually, pulmonary function tests have shown a restrictive pattern, resulting from chest wall involvement and/or encasement of the lung.
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