A PROPOSED NEW INTERNATIONAL TNM STAGING SYSTEM FOR MALIGNANT PLEURALMESOTHELIOMA FROM THE INTERNATIONAL MESOTHELIOMA INTEREST GROUP

Study objective: investigation of the behavior and treatment of diffus e malignant pleural mesothelioma (MPM) is hindered by the lack of an a ccurate universally accepted staging system, To address this problem, the International Mesothelioma Interest Group (IMIG) has developed a n ew TNM based staging system. Methods: the staging system was developed at a consensus meeting of IMIG members involved in clinical research in MPM, including the originators of previously proposed staging syste ms, The new staging system is based on the analysis of emerging inform ation about the impact of T and N status on survival. Results: in cont rast to five previous staging systems, the T descriptors designated as T1, T2, T3 and T4, provide precise anatomic definitions of the local extent of the primary tumour. The N descriptors, designated as N0, N1, N2 and N3, are virtually identical to those used in the International Lung Cancer Staging System. The stage groupings recognize new data ab out the better prognosis of T1 and N0 tumours and classify those tumou rs into stages I and II. The adverse impact of nodal metastases on sur vival noted in some recent surgical series warrants placing node posit ive tumours in stage III. Locally advanced unresectable (T4) tumours a nd extrathoracic disease (N3 or M1) are classified as stage IV. Conclu sion: this proposed staging system reconciles and updates several earl ier systems, and can provide the framework for analyzing the results o f prospective clinical trials aimed at improving the currently dismal prognosis of MPM.