The IASLC Mesothelioma Staging Project: Proposals for Revisions of the N Descriptors in the Forthcoming Eighth Edition of the TNM Classification for Pleural Mesothelioma

Journal of Thoracic Oncology 2016 September 23 [Epub ahead of print] [Link]

Rice D, Chansky K, Nowak A, Pass H, Kindler H, Shemanski L, Opitz I, Caja SC, Hasegawa S, Kernstine K, Atinkaya C, Rea F, Nafteux P, Rusch V; Staging and Prognostic Factors Committee, Advisory Boards and Participating Institutions


Nodal categories for malignant pleural mesothelioma (MPM) are derived from the lung cancer staging system and have not been adequately validated. The International Association for the Study of Lung Cancer (IASLC) developed a multinational database to generate evidence-based recommendations to inform the 8th edition of the tumor, node metastasis classification of MPM.
Data from 29 centers were entered prospectively (n=1,566) or by transfer of retrospective data (n=1,953). Survival according to the 7th edition N categories was evaluated using Kaplan-Meier (KM) survival curves and Cox proportional hazards regression analysis. Survival was measured from the date of diagnosis.
There were 2,432 analyzable cases: 1,603 had clinical (c) staging; 1,614 had pathologic (p) staging; and 785 had both. For clinically staged tumors there was no separation in KM curves between cN0, cN1 or cN2 (cN1 vs. cN0 HR 1.06, p=0.77 and cN2 vs. cN1 HR 1.04, p=0.85). For pathologically staged tumors, patients with pN1 or pN2 tumors had worse survival than those with pN0 tumors (HR 1.51, p<0.0001) but no survival difference was noted between those with pN1 and pN2 (HR 0.99, p=0.99). Patients with both pN1 and pN2 nodal involvement had poorer survival than those with pN2 only (HR 1.60, p=0.007) or pN0 (HR 1.62, p<0.0001). CONCLUSIONS: A recommendation to collapse both clinical and pathological N1 and N2 categories into a single N category comprising ipsilateral, intrathoracic nodal metastases (N1) will be made for the 8th edition staging system. Nodes previously categorized as N3 will be reclassified as N2.