Evaluation of the proposed International Association for the Study of Lung Cancer (IASLC)/International Thymic Malignancies Interest Group (ITMIG) staging revisions in thymic well-differentiated neuroendocrine carcinoma patients

In 2014, the International Association for the Study of Lung Cancer (IASLC)/International Thymic Malignancies Interest Group (ITMIG) launched a worldwide Tumor Node Metastasis (TNM) staging proposal for the next edition of thymic tumours. The objective of the current study was to evaluate the proposed new staging system specific to the thymic well-differentiated neuroendocrine carcinoma (TWDNC). From November 2003 to July 2014, 61 consecutive patients were enrolled in this study with pathologically confirmed TWDNC in Shanghai Chest Hospital. Clinical and pathological data were retrospectively reviewed. Survival analysis was performed using the Kaplan-Meier and log-rank tests. Validity evaluation was addressed by Cox proportional hazards regression model, after adjusting for potential confounders and visually assessing the distinction of curves generated based on the staging system of Masaoka-Koga and the proposed TNM ones. Thymic carcinoids made up 4% of total thymic tumours in our institution. The 5-year overall survival (OS) rate and the disease-free survival (DFS) rate were 72 and 41%, respectively. Neither Masaoka-Koga staging system nor the proposed TNM system showed ordered appropriateness visually in survival curves and the prognostic demarcation between stages was poor on both OS and DFS. The IASLC/ITMIG suggested that the TNM and Masaoka-Koga staging systems fail to predict the clinical course of TWDNC patients. Collaborative effort is needed in the future staging validation as ITMIG recommended.