Is the Burden of Metastatic Lymph Node Stations a Prognostic Factor in Patients with Resected Lung Cancer? A Multicentre Study with Validation in Each T Stage

Abstract

Objectives The burden of metastatic lymph node (LN) stations might reflect a distinct N subcategory with a more aggressive biology and behaviour than the traditional N classification. Methods Between 2008 and 2018, we analysed 1236 patients with pN1/2 lung cancer. When survival was analysed according to LN station metastasis, the number of metastatic LN stations that provided additional prognostic information was considered the optimal threshold. We performed the N prognostic subgrouping according to the thresholds for the number of metastatic LN stations with a maximum chi-square log-rank value. This was validated at each pT-stage. Results Survival showed stepwise statistical deterioration with an increase in the number of metastatic LN stations. According to survival analyses results, threshold values for the number of metastatic LN stations were determined and N prognostic subgrouping was created as sN-αlfa; one LN station metastases (n = 632), sN-βeta; two-three LN stations metastases (n = 505), and sN-Ɣamma; ≥4 LN stations metastasis (n = 99). The 5-year survival rate was 57.7% for sN-αlfa, 39.2% for sN-βeta, and 12.7% for sN-Ɣamma (chi-square log rank = 97.906, p < 0.001). We observed a clear tendency of deterioration of survival from sN-αlfa to sN-Ɣamma in the same pT stage, except for pT4 stage. Multivariate analysis showed that age (p < 0.001), sex (p = 0.002), tumour histology (p < 0.001), IASLC-proposed N subclassification (p < 0.001), and sN prognostic subgroups (p < 0.001) were independent risk factors for survival. Conclusion The burden of metastatic LN stations is an independent prognostic factor for survival in patients with lung cancer and could add different prognostic information to the N classification.