Clinical evaluation of a new tumour-node-metastasis staging system for thymic malignancies proposed by the International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee and the International Thymic Malignancy Interest Group.

Abstract

The tumour-node-metastasis classification has been widely used as a guide for estimating prognosis, and is the basis for treatment decisions in patients with malignant tumours. The International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee and the International Thymic Malignancy Interest Group have proposed a new staging system for thymic malignancies. However, its validity has not been fully established. In this study, we assessed the system's utilities and drawbacks. We reviewed 154 consecutive patients with thymic epithelial tumours who underwent complete resection at our institution, and compared their characteristics and outcomes when classified according to the proposed system with those when classified under the Masaoka-Koga system. The proportion of patients with Stage I disease increased remarkably to 77.3% when using the proposed system because of the reclassification of Masaoka-Koga stages II and III diseases. Among 69 patients with Type A, AB or B1 thymoma, 68 tumours (98%) were reclassified as Stage I disease. Moreover, the proportion of Stage III and IV tumours increased in concordance with Types B2, B3 thymomas and thymic carcinoma. Under the proposed new system, the recurrence-free survival rates showed significant deterioration with increasing stage, while the overall survival curves did not. The newly proposed classification for thymic malignancies does not serve as a prognostic prediction model for overall survival but served as a significant imbalance of stage distribution in our cohort. However, it appears to be beneficial, especially in clinical settings and recurrence-free survival analysis.