Evaluation of the Prognostic Significance of TNM Staging Guidelines in Lung Carcinoid Tumors

Introduction: The TNM classification for lung cancer, originally designed for NSCLC, is applied to staging of bronchopulmonary carcinoid tumors. The validity of the eighth edition of the staging system for carcinoid tumors has not been assessed. In this study, we evaluated its prognostic accuracy by using data from a large national population-based cancer registry. Methods: Patients with typical and atypical bronchopulmonary carcinoids diagnosed between 2000 and 2013 were identified from the National Cancer Institute's Surveillance, Epidemiology and End Results registry. We used competing risks analysis to compare 10-year disease-specific survival (DSS) across stages. Results: Overall, 4645 patients with bronchopulmonary carcinoid tumors were identified. Worsening DSS with increasing TNM status and stage was demonstrated across both typical and atypical carcinoids, with overlaps between adjacent subcategories. The combined stages (I versus II, II versus III, and III versus IV) showed greater separation in DSS despite persistent overlaps between groups. For typical carcinoids, we found decreased DSS for stages II, III, and IV, with hazard ratios of 3.8 (95% confidence interval [CI]: 2.6–5.6), 4.3 (95% CI: 3.0–6.1), and 9.0 (95% CI: 6.1–13.1), respectively, compared with stage I. Conclusion: The combined stage categories of the eighth edition of the TNM staging system provide useful information on outcomes for typical and atypical carcinoids. However, persistent overlaps in combined stage and subcategories of the staging system limit the usefulness of the TNM staging system, particularly in intermediate stages. These limitations suggest the need for future further study and refinement.