Skip Hilar Lymph Node Metastasis in Non-Small Cell Lung Cancer Has Similar Survival to N0 Disease: Need for a Change in the pN Sub-classification?

Introduction

Previous edition of TNM lung cancer staging system divided N1 disease into two subgroups: N1a and N1b. Our study aimed to investigate the survival difference between patients with hilar lymph node metastasis only (skip metastasis) and other N1a patients.

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Methods

Patients with NSCLC who were operated between February 2003 and February 2019 were retrospectively analyzed. Patients who have oligometastases or neoadjuvant treatment were excluded. A total of 629 patients were investigated in terms of lymph node metastasis status. Overall survival (OS) of skip hilar was compared to N0 and other N1 patients. Kaplan Meier was used for the analysis with 95% confidence intervals.

Results

There were 470 patients with N0 disease. Patients with N1 disease (n=159) were divided into three groups. Group 1 has 89 skip hilar lymph node metastasis, Group 2 has 41 patients with N1a disease without the skip hilar metastasis and Group 3 has 29 patients with N1b disease. OS of the patients with skip hilar lymph node metastasis was 129 months (95% Confidence Interval: 114-143 months) similar to N0 patients with an OS of 133 months (95% Confidence Interval: 125-142 months) (p=0,013). This was 

Conclusions

Skip hilar lymph node metastasis has a similar survival to N0 disease and is significantly better than non-skip N1 disease. Therefore we are suggesting a change in pN sub-classification for the 9th edition of TNM staging studies. We suggest that patients with skip hilar lymph node metastasis should be staged as pN1a1. The mechanism behind this prognostic advantage and verification of our findings need further studies with larger patient series.

Keywords

pN sub-classification, N1 disease, lymph node metastasis