Prognostic Value of Preoperative N Subcategories in Patients with Stage IIIA N2 Non–Small Cell Lung Cancer

Purpose To evaluate the preoperative risk factors in patients with pathologic IIIA N2 non-small cell lung cancer (NSCLC) who underwent upfront surgery and to evaluate the prognostic value of new N subcategories. Materials and Methods Patients with pathologic stage IIIA N2 NSCLC who underwent upfront surgery in a single tertiary center from January 2015 to April 2021 were retrospectively reviewed. Each patient's clinical N (cN) was assigned to one of six subcategories (cN0, cN1a, cN1b, cN2a1, cN2a2, and cN2b) based on recently proposed N descriptors. Cox regression analysis was used to identify the significant prognostic factors for recurrence-free survival (RFS) and overall survival (OS). Results A total of 366 patients (mean age ± SD, 62.0 years ± 10.1; 202 male patients [55%]) were analyzed. The recurrence rate was 55% (203 of 366 patients) over a median follow-up of 37.3 months. Multivariable analysis demonstrated that cN (hazard ratios [HRs] for cN1 and cN2b compared with cN0, 1.66 [95% CI: 1.11, 2.48] and 2.11 [95% CI: 1.32, 3.38], respectively) and maximum lymph node (LN) size at N1 station (≥12 mm; HR, 1.62 [95% CI: 1.15, 2.29]), in addition to clinical T category (HR, 1.51 [95% CI: 1.14, 1.99]), were independent prognostic factors for RFS. For OS, clinical N subcategories (cN1, cN2a2, and cN2b vs cN0; HRs, 1.91 [95% CI: 1.11, 3.27], 1.89 [95% CI: 1.13, 2.18], and 2.02 [95% CI: 1.07, 3.80], respectively) and LN size at N1 station (HR, 1.75 [95% CI: 1.12, 2.71]) were independent prognostic factors. For clinical N1, OS was further stratified according to LN size (log-rank test,