Validation of the 9th edition of the TNM staging system for limited-stage small cell lung cancer after Resection: A multicenter study

Objectives: The 9th edition of the tumor-node-metastasis (TNM) staging system for lung cancer was proposed at the 2023 World Conference on Lung Cancer in Singapore. This study aimed to externally validate and compare the latest staging of small-cell lung cancer (SCLC).

Methods: Four hundred and eight patients with limited-stage SCLC were collected after lung resection from four centers. Survival curves by TNM stages were drawn using the Kaplan-Meier method and further compared by the Log-rank test. The Cox regression, receiver operating characteristics curves, area under the curve (AUC), Akaike information criterion (AIC), Bayesian information criterion (BIC), and Concordance index (C-index) were used in this study.

Results: In comparing IA vs. IIB, IIA vs. IIB, IIA vs. IIIA, IIA vs. IIIB, and IIIA vs. IIIB, the 9th edition had a better distinguishing ability than the eighth staging system (all p < 0.05). Besides, the 9th edition TNM staging had better predictive power and accuracy for the overall survival (OS) of SCLC patients over the 8th edition (AUC of 3-year OS: 0.680 vs. o.668; AIC: 4425.25 vs. 4444.52; BIC: 4493.44 vs. 4512.71; C-index: 0.637 [0.04] vs. 0.629 [0.039], p < 0.001).

Conclusions: Our external validation demonstrates that the ninth edition of pathological TNM staging for limited-stage SCLC is reasonable and valid based on a multicenter study. The ninth edition has better prognostic accuracy than the eighth edition.