The International Association for the Study of Lung Cancer Mesothelioma Staging Project: Proposals for the "N" Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Pleural Mesothelioma.

Introduction: The International Association for the Study of Lung Cancer developed an international database to inform potential revisions in the ninth edition of the TNM classification of diffuse pleural mesothelioma (PM). This study analyzed the clinical and pathologic N categories to determine whether revisions were indicated relative to the eighth edition staging system.
Methods: Of 7338 PM cases diagnosed from 2013 to 2022 and 3598 met all inclusion criteria for planned analyses. Data on 2836 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 pathologic N analysis, patients who underwent resection (extrapleural pneumonectomy or pleurectomy/decortication) were included. N subgroups were analyzed and OS assessed by the Kaplan-Meier method.
Results: The existing eighth edition N categories were performed adequately in the ninth edition data set. A median OS advantage was noted for clinical and pathologic N0 versus N1 patients: 23.2 versus 18.5 and 33.8 versus 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.
Conclusions: Data regarding clinical and pathologic N categories corroborate those used in the eighth edition. No changes in the N categories are recommended in the ninth edition of PM staging system.
Competing Interests: Disclosure Dr. Pass reports serving on the steering committee and speakers bureau of Roche and serving on the advisory board of AstraZeneca. Dr. Ripley reports receiving institutional clinical trial funding from AstraZeneca and serving on the speakers’ bureau of Merck. Dr. Rusch reports receiving institutional clinical trial funding from Genentech; having meeting preparation and receiving travel reimbursement from NIH/NCI Thoracic Malignancy Steering Committee; and serving as an unpaid member, DSMC Committee, MARS II trial (Cancer Research UK). Dr. Opitz reports receiving an institutional grant and serving on the speakers’ bureau of Roche; serving on the advisory board and speakers’ bureau of AstraZeneca; serving on the advisory boards of Merck Sharp & Dohme and Bristol-Myers Squibb; receiving an institutional grant from Medtronic; and having proctorship from Intuitive. The remaining authors declare no conflict of interest.
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