Non-Small Cell Lung Cancer With N1 Involvement or Skip Metastases Presents the Same Survival Outcome: Results From a Multicentric Study

Background: The prognostic difference among patients affected by NSCLC with hilar metastases only or mediastinal nodes metastases without hilar involvement (skip metastases) is still unclear. Aim of this study is to analyse if prognostic difference are present or if the two groups present the same survival outcome. Materials and methods: Data on NSCLC patients from 7 high volume centres (2004-2014) were collected and retrospectively reviewed. Histology different from adenocarcinoma(ADC) or squamous cell carcinoma(SCC), patients without data on lymphadenectomy, who underwent neoadjuvant treatment, with distant metastases or incomplete resection were excluded, selecting patients with hilar involvement or with skip metastases. Different prognostic factors such as Tstage, histology, pathological stage, nodal characteristics and adjuvant therapy administration were correlated to overall survival (OS) by the Kaplan-Meier product-limit method. The log-rank test was used to assess differences between subgroups. A multivariable Cox proportional hazard model was developed using stepwise regression to compare the prognostic power of different factors. Results: The final analysis was conducted on 480 adenocarcinoma/squamous cell carcinoma patients. Five-year OS (5YOS) resulted 53.9%. No significant differences in OS were detected comparing pN1 vs. pN2 patients or stage IIB vs. stage IIIA-B patients. Univariable confirmed as favourable prognostic factors young age (P<.001), T1-2 tumors (P=.030), number of resected nodes≥10 (P=.040), lymph node ratio (P=.026). Multivariable analysis confirmed as independent negative prognostic factors T≥3 (HR:1.385, 95%CI:1.037-1.851, P=.027) and age≥68 years (HR1.637, 95%CI:1.245-2.152). Conclusion: Patients with N1 involvement or skip metastases present a similar prognosis, suggesting that N2 involvement in these cases may be related to a direct lymphatic drainage to the mediastinal stations.