The International Association for the Study of Lung Cancer Thymic Tumors Staging Project: The Impact of the Eighth Edition of the Union for International Cancer Control and American Joint Committee on Cancer TNM Stage Classification of Thymic Tumors

Objectives: The International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee-Thymic Domain conducted a web-based cross-sectional survey to assess the acceptance of the TNM thymic staging system in the thoracic community. Methods: A 50-item, web-based questionnaire was circulated among the members of the major thymic organizations worldwide from September to December 2018. The survey consisted of six sections (general information; overall perception of the TNM system; pretreatment staging; T category; N category; and perioperative treatments). Results: In total, 217 responses were collected from 37 countries in four continents. The TNM classification was considered useful by 78% of the responders (N = 169); the Masaoka-Koga staging system was being used by 87% of the responders (N = 189). With regard to the T category, most responders (mostly surgeons) felt that the capsular and mediastinal pleural involvements should be considered separate T categories. As for the N category, 48% of the responders (N = 105) used the International Thymic Malignancies Interest Group/International Association for the Study of Lung Cancer thymic nodal map, and lymph node dissection (N1/N2) was performed for 50%/21% thymomas and 66%/41% thymic carcinomas. While analyzing the results by the three continents (Europe, Asia, and Americas), responders in Asia were found to report the largest use of the TNM system, the greatest attention to the N category, and the best participation in international thymic databases. Conclusions: The survey indicates that the Union for International Cancer Control/American Joint Committee on Cancer TNM stage classification of thymic tumors is gaining acceptance among the scientific community. The present results will guide the work of the Staging and Prognostic Factors Committee-Thymic Domain for the revision of the ninth edition of the TNM stage classification of thymic tumors.