The revised staging system for malignant pleural mesothelioma based on surveillance, epidemiology, and end results database.

BACKGROUND: Several staging systems for MPM have been introduced. However, none of them provide perfect survival stratification among heterogeneous patients. The aim of this population-based cohort study was to propose adjustments to current staging system for malignant pleural mesothelioma (MPM).

METHODS: We retrieved MPM data from Surveillance, Epidemiology, and End Results database (1973-2014). Kaplan-Meier method was derived to examine the prognostic effects of tumor, lymph node, metastasis and histology features. Proportional hazards models guided adjustments to stage groupings. The accuracy of staging systems at predicting survival was evaluated by concordance index and bootstrap resampling.

RESULTS: A total of 1110 MPM cases were extracted from SEER. T stage failed to demonstrate survival difference between adjacent categories with the exception of T3 versus T4 (P < 0.001). Patients in M0 had better prognosis than those in M1 (P < 0.001). Exploratory analyses suggested important survival difference for single-versus multiple-site M1 cases (P < 0.001), but not for different metastatic sites (P = 0.286). Histology subtype was a significant prognostic indicator (P < 0.001). Regrouping of TNM and histology combinations resulted in the best concordance index (0.683), compared with UICC 2010 (0.578) and IASLC 2016 (0.585) staging systems. The revised staging system also improved patients distribution (IA:33.8%, IB:17.0%, II: 20.7%, IIIA:10.6%, IIIB: 6.8%, IV:11.1%). Log-rank analyses and calibration plots both demonstrated the new stage achieved optimal survival prediction and discrimination.

CONCLUSION: The revised staging system improved patients distribution and survival stratification for MPM.