RA10.06: THE ROLE AND PROGNOSTIC SIGNIFICANCE OF AORTOPULMONARY, ANTERIOR MEDIASTINAL, AND TRACHEOBRONCHIAL LYMPH NODES IN ESOPHAGEAL CANCER: UPDATE OF THE 2018 TNM STAGING SYSTEM
Authors: Wang Wen-Ping , Yang Yu-Shang , He Song-Lin , Hu Wei-Peng , Chen Long-Qi 
Published: September 2018

Abstract

Background
The eighth edition of the American Joint Committee on Cancer TNM staging for esophageal cancer will be implemented at the beginning of 2018. The nodal staging process in the eighth edition remains unchanged from that in the seventh edition in that it was based on the number of lymph nodes (LNs) involved, but the regional lymph node map has been revised. The aortopulmonary (station 5), anterior mediastinal (station 6), and tracheobronchial (station 10) nodes have been omitted from the regional lymph node map for the new TNM staging. However, the role and prognostic significance of these LN stations are not clear. The purpose of this study was to investigate whether the revised nodal staging used in the eighth edition staging system is appropriate, and to verify the role, prognostic significance, and therapeutic value of these LNs in esophageal cancer.

Methods
The records of patients who underwent esophagectomy for cancer in our department between January 2007 and January 2013 were retrospectively analyzed. The rate of metastases and the index of estimated benefit from lymph node dissection (IEBLD) were calculated for stations 5, 6, and 10 LNs. LN metastasis and patient survival were analyzed and the efficacy of the eighth edition TNM staging system was verified.

Results
A total of 1637 patients (1350 men, 287 women) were included. The frequencies of dissection of stations 5, 6, and 10 LNs were 34.3% (562/1637), 15.9% (260/1637), and 50.9% (833/1637), respectively. The calculated rate of metastasis to these stations was 3.2% (18/562), 2.3% (6/260), and 4.9% (41/833), respectively. No difference was found in the N stage determined by the seventh and eighth edition N staging systems. The survival curves differed significantly between N stages calculated using the eighth edition TNM system (P < 0.001). The IEBLD values of stations 5, 6, and 10 LNs were 0.57, 0, and 0.97, respectively. Station 5 or 10 LN(+ ) patients had worse median survival time and 5-year overall survival rate compared with LN(–) patients (P < 0.01). Univariate analysis showed that differentiation, T stage, N stage (both seventh and eighth edition calculations), and metastasis to stations 5 and 10 LNs were associated with long-term survival.

Conclusion
Metastasis to stations 5, 6, or 10 LNs was infrequent. If stations 5, 6, and 10 LNs were omitted in the eighth edition calculation to determine the N stage based on the number of metastatic LNs, this did not influence the accuracy and survival-predicting efficacy of the eighth edition TNM staging. The therapeutic value of lymphadenectomy of stations 5, 6, and 10 was limited. Metastasis to stations 5, 6, and 10 LNs indicated more advanced N stage, which was associated with poor survival. However, no survival difference was found between station 6 LN(+ ) and LN(–) subgroups, possibly because of the limited numbers of cases.

Disclosure
All authors have declared no conflicts of interest.