OBJECTIVES: The 9th edition of the lung cancer tumor-node-metastasis (TNM) staging system downgrades certain non-small cell lung cancer (NSCLC) patients from stage IIIA (T1N2) to IIB(T1N2a). This study aimed to externally validate this stage adjustment. METHODS: Consecutive resected stage IIB and IIIA (the 9th edition of lung cancer TNM staging manual) NSCLC patients were included. Stage IIB was divided into groups A, B, and C according to lymph node involvement. Group A, patients who having single-station N2 without N1 involvement
Group B, patients who having single-station N2 with N1 involvements
Group C, patients who having station N1 involvement or N0. The stage IIIA patients divided into Group D. Overall survival (OS) and disease-free survival (DFS) were compared using the Kaplan-Meier method, with propensity score matching (PSM) employed to mitigate potential biases. COX regression models were utilized to assess prognostic differences. RESULTS: 224 stage IIB and 227 stage IIIA cases was included. There were 38, 66 and 120 patients in the Group A, B and C, respectively. Univariate COX analysis indicated comparable prognoses between the Group A and Group C patients, whereas Group B patients exhibited poorer outcomes. Upon combining the Group A and Group C patients, multivariate COX analysis demonstrated a significantly worse prognosis for Group B patients compared to those with Group A + C patients (OS, P = 0.035
DFS, P = 0.021). Further comparisons between Group B and Group D patients, following PSM analysis, indicated similar survivals (OS: P = 0.390
DFS: P = 0.210). CONCLUSION: In the 9th edition of the lung cancer TNM staging system, the prognosis of stage IIB N2a2 patients was worse than that of remaining stage IIB patients but comparable to that of stage IIIA patients. We proposed that stage IIB N2a2 patients should be maintained as stage IIIA.