Published online Mar 7, 2018. doi: 10.3748/wjg.v24.i9.1022
Peer-review started: December 23, 2017
First decision: January 17, 2018
Revised: January 30, 2018
Accepted: February 8, 2018
Article in press: February 8, 2018
Published online: March 7, 2018
Lymph node (LN) status was determined to be a strong predictor for the prognosis of patients with distal cholangiocarcinoma. However, the prognostic value of the retrieved LNs counts in distal cholangiocarcinoma is still under debate.
The benchmark number of retrieved LNs has been determined in many gastrointestinal carcinomas, in addition to the distal cholangiocarcinomas. Previous studies regarding the retrieved LNs counts in distal cholangiocarcinomas were limited by their small sample size, and the patients in those studies comprised both perihilar and distal cholangiocarcinomas. The present study tried to determine the interactions between the retrieved LNs counts and the prognosis in patients with only distal cholangiocarcinomas, and a population-based database was used for patients’ selection that provided a sufficient sample size.
We aimed to evaluate the prognostic value of the number of retrieved LNs for patients with distal cholangiocarcinomas and to determine the optimal retrieved LNs cut-off number.
The Surveillance, Epidemiology and End Results (SEER) database was used to screen for patients with distal cholangiocarcinoma. The retrieved LNs counts were transformed from continuous variables to categorical variables, and the cut-off was defined by the X-tile program. The overall and cancer-specific survival was compared between the different categories of retrieved LNs counts by the means of the Kaplan-Meier method and Cox regression analysis. Then, we performed stratified analyses by the clinical factors that were evaluated to be independently associated with survival in the Cox regression analysis, among patients within the different LNs groups.
A total of 449 patients with distal cholangiocarcinoma were included in the present study. The Kaplan-Meier survival analysis for all patients and for N1 patients revealed no significant differences among patients with different retrieved LN counts in terms of overall and cancer-specific survivals. In patients with node-negative distal cholangiocarcinoma, patients with four to nine retrieved LNs had a significantly better overall (P = 0.026) and cancer-specific (P = 0.039) survival than others. In the subsequent multivariate analysis, the number of retrieved LNs was evaluated to be independently associated with survival. Additionally, patients with four to nine retrieved LNs had a significantly lower overall mortality risk (hazard ratio (HR): 0.39; 95% confidence interval (CI): 0.20-0.74) and cancer cause-specific mortality risk (HR: 0.32; 95%CI: 0.15-0.66) than other patients. Additionally, stratified survival analyses showed persistent better overall and cancer-specific survival when retrieving four to nine LNs in patients with any T stage of tumor, a tumor between 20 and 50 mm in diameter, or a poorly differentiated or undifferentiated tumor and in patients who were ≤ 70-years-old.
The number of retrieved LNs was an important independent prognostic factor for patients with node-negative distal cholangiocarcinoma. Additionally, patients with four to nine retrieved LNs had a better overall and cancer-specific survival rate than patients with less than four or more than nine retrieved LNs.
Although our study revealed retrieving four to nine LNs in patients with node-negative distal cholangiocarcinoma had better overall and cancer-specific survival rates than others, the reason and mechanism for that were unclear. The future studies should consider more operation- and adjuvant therapy-related parameters into their analysis to evaluate our results.