CT imaging of the chest and abdomen is recommended in all patients. Fluoro-deoxyglucose positron emission tomography is reserved for patients being considered for surgery to exclude extrathoracic spread. It is not used universally for staging, since there can be false positivity from nonmalignant processes including pleural inflammation from pleurodesis. Magnetic resonance imaging can be helpful in evaluating patients with suspected vascular, diaphragmatic, or spine invasion.
Candidates for surgical resection will also undergo additional procedures to exclude contralateral pleural disease, extrathoracic spread, or peritoneal involvement. Mediastinoscopy or endobronchial ultrasound fine needle aspiration of mediastinal lymph nodes is recommended. Additional studies include video-assisted thoracoscopy to exclude extension into the contralateral lung and laparoscopy to exclude transdiaphragmatic extension into the peritoneal cavity. In a series of 118 possible surgical candidates with MPM, laparoscopy was performed in 109 patients, and ten (9.2%) had incidental peritoneal involvement.30
MPM is a highly aggressive disease with a dismal prognosis with reported median survivals of 6–12 months and <5% of patients surviving >5 years.5,15,31 Both the European Organization for the Research and Treatment of Cancer (EORTC) and the Cancer and Leukemia Group B (CALGB) have published prognostic scoring systems for this disease.32,33 Both scoring systems were established in cohorts of previously untreated patients enrolled in Phase II trials of chemotherapy and have been subsequently validated in independent cohorts.34,35 In a multivariate analysis, the CALGB identified the following as independent predictors of poor outcome: pleural primary site, lactate dehydrogenase >500 IU/L, Eastern Cooperative Oncology Group (ECOG) performance status >0, platelet count >400,000/μL, non-epithelial histology, and age >75 years. Six prognostic subgroups were identified with median survivals that ranged from 1.4 to 13.9 months (Table 2). The best prognostic subgroup included patients with either an ECOG performance status of 0 and age <49 years or an ECOG performance status of 0, age >49 years, and a hemoglobin >14.6 g/dL. The worst survival was seen in patients with an ECOG performance status of 1 or 2 and a white blood cell count >15.6/μL. The EORTC model also identified ECOG performance status >0 and sarcomatoid histology along with an elevated white blood cell count, male sex, and possible/probable diagnosis of mesothelioma (as opposed to a definite diagnosis) as independent predictors of poor outcome in multivariate analysis. This model classified patients into two groups: a low-risk group with a median survival of 10.8 months and a high-risk group with a median survival of 5.5 months (Table 3). In addition to the clinical factors reviewed, multiple groups have attempted to evaluate potential molecular predictors of prognosis, including gene expression analyses.36 However, to date, none have shown enough promise to be in routine clinical use.
(To view a larger version of Table 2, click here.)
(To view a larger version of Table 3, click here.)