The IASLC Mesothelioma Staging Project: Proposals for the ‘N’ descriptors in the forthcoming 9th edition of the TNM classification for Pleural Mesothelioma

Abstract

IntroductionThe International Association for the Study of Lung Cancer developed an international database to inform potential revisions in the 9th edition of the Tumor, Node, Metastasis classification of diffuse pleural mesothelioma (PM). This study analyzed the clinical and pathological N categories to determine whether revisions were indicated relative to the 8th edition staging system. MethodsOf 7,338 PM cases diagnosed 2013 to 2022, 3,598 met all inclusion criteria for planned analyses. Data on 2,836 patients without metastases were included in this study. Overall survival (OS) was measured from date of diagnosis. Patients were included regardless of whether they received neoadjuvant treatment. For the pathological N analysis, patients who underwent resection (extrapleural pneumonectomy or pleurectomy/decortication) were included. N subgroups were analyzed and overall survival (OS) assessed by the Kaplan Meier method. ResultsThe existing 8th edition N categories performed adequately in the 9th edition dataset. A median OS advantage was noted for clinical and pathological N0 versus N1 patients: 23.2 versus 18.5 and 33.8 vs. 25.0 months, respectively. Patients with resected pN0 had a 3-year OS of 48%. No difference in OS was noted for single versus multiple station nodal metastases. The number of nodal stations sampled at the time of resection was not associated with a difference in OS. ConclusionsData regarding clinical and pathological N categories corroborate those used in the 8th edition. No changes in the N categories are recommended in the 9th edition of PM staging system.