Background: Several pathologic staging systems for malignant pleural mesothelioma (MPM) have been published, but none of them provide optimal survival stratification or stage distribution among patients treated with surgery. Interpretation of prior studies that correlate pathologic factors with outcome has been confounded by the inclusion of patients undergoing differing surgical procedures and with varied tumor histology.
Methods: We examined pathologic characteristics, previously included in published studies, and explored correlations with outcome among patients with epithelioid MPM who underwent extrapleural pneumonectomy (EPP) at Brigham and Women's Hospital (BWH). Comparisons of survival among patients with and without each tumor or lymph node feature guided adjustments to the American Joint Commission on Cancer (AJCC)/International Union Against Cancer (UICC) classification criteria. Proportional hazards modeling of TN combinations guided adjustments to stage groupings.
Results: Three hundred fifty-four patients were resectable by EPP and had complete pathologic data. Overall median survival was 18 months from surgery. By AJCC/UICC criteria, 233 (66%) patients were stage III, whereas by BWH criteria, 194 (55%) patients were stage III. T classification criteria were adjusted based on prevalence and relation to survival. N status correlated significantly with survival. Regrouping of TN combinations based on relative hazard and Kaplan-Meier survival analysis resulted in improved stage distribution (stage I-IV: 8%, 43%, 33%, 16%, respectively) and survival stratification (51, 26, 15, 8 months, respectively).
Conclusions: Proposed adjustments to TNM staging criteria improved outcome stratification of patients with epithelial tumor histology who received surgical therapy by EPP and complete pathologic assessment. Determining relevance to other treatment or staging modalities will require verification in additional cohorts.