Which N descriptor is more predictive of prognosis in resected non-small cell lung cancer: the number of involved nodal stations versus the location-based pathological N stage?
The eighth edition of nodal classification for non-small cell lung cancer (NSCLC) is defined only by the anatomical location of metastatic lymph nodes.We sought to evaluate the prognostic significance and discriminatory capability of the number of involved nodal stations (nS) in a large Chinese cohort.A total of 4,011 NSCLC patients undergoing surgical resection between 2009 and 2013 were identified. The optimal cut-off values for nS classification were determined using X-tile software. Kaplan-Meier and multivariate Cox analysis were used to examine the prognostic performance of the nS classification in comparison with the location-based N classification. A decision curve analysis (DCA) was performed to evaluate the standardized net benefit of nS classification in predicting prognosis.All the patients were classified into four prognostically different subgroups according to the number of involved nodal stations: (1) nS0 (none positive), (2) nS1 (one involved station), (3) nS2 (two involved stations), and (4) nS ≥ 3 (three or more involved stations). The prognosis among all the neighboring categories of nS classification were statistically different in terms of disease-free survival (DFS) and overall survival (OS). The multivariate Cox analysis demonstrated that nS was an independent prognostic factor of DFS and OS. Patients belonging to N1 or N2 stage could be divided into three prognostically different subgroups according to nS classification. However, the prognosis was similar between N1 and N2 subgroups when patients staging in the same nS category. The DCA showed that the nS classification tended to have a higher predictive capability than the location-based N classification.The nS classification could be used to provide a more accurate prognosis in patients with resected NSCLC. The nS is worth taking into consideration when defining nodal category in the forthcoming ninth edition of the staging system.