The aging of the population and a longer life expectancy have led to more elderly patients with cancers being referred for treatment. For many of them, in particular for those with EC, surgery remains the mainstay of treatment. There is no established cutoff to define a patient as “elderly” in relation to surgery, but most studies available to date have set the age limit at 70 years [7, 8]. In our study, we determined the prognostic value of MLNR compared with N staging in EC patients older than 70 years of age. Our results suggest that MLNR might be a valuable prognostic factor of survival in elderly patients in EC. We conclude that MLNR staging predicts survival after EC similar to the AJCC Seventh Edition N staging classifications and should be considered as an alternative to current pathological N staging. To the best of our knowledge, our present studymay be the first to evaluate the value of MLNR vsAJCC Seventh EditionN staging in elderly patients with EC.
The ratio of metastatic to total lymph nodes (that is, the MLNR) has been shown to be a prognostic factor in EC, but the value of MLNR that is most predictive of survival is being debated. Most of the studies published to date concerning the MLNR and survival have been based on the AJCC Sixth Edition classification system [3–5]. Furthermore, in terms of MLNR and survival, some studies have classified the MLNR into three groups, whereas other studies have used two classifications. In our study, the MLNR was categorized by deciles into 0 (MLNR0), >0 to <0.1 (MLNR1), 0.1 to <0.3 (MLNR2) and ≥0.3 (MLNR3), based on the AJCC Seventh Edition classification system. We developed the MLNR intervals on the basis of our data to provide clinically relevant MLNR strata while probing to identify the subset of MLNR with the greatest predictive potential. In our study, the disease-specific survival rates of MLNR0, MLNR1, MLNR2 and MLNR3 patients were 65.5%, 45.0%, 21.1% and 0, respectively (MLNR0vs MLNR1, P = 0.026; MLNR1 vs MLNR2, P = 0.033; MLNR2 vs MLNR3, P = 0.015). Wilson et al.  classified 144 patients into 4 groups according to MLNR: 0, ≤25%, >25 to ≤50% and > 50%. Althoughan increasing MLNR was linearly associated with a worsening 5-yr survival rate in their study, statistical significance was not achieved (P = 0.153). Bogoevski et al.  also classified 235 patients into four categories according to MLNR: 0, <11%, 11% to 33% and >33%, which is similar to our findings.
The question of how many lymph nodes should be dissected has been a point of debate in previous studies. Rizk et al.  reported that the prognosis of patients after esophagectomy worsens significantly after four or more lymph nodes have metastases, irrespective of T stage. Greenstein et al.  and Yang et al.  recommended 18 nodes as the minimum number of resectable lymph nodes, whereas Peyre et al.  recommended a minimum of 23 regional lymph nodes. Attendees at a consensus conference of experts in 1995 suggested that accurate pathological staging of EC requires resection of at least 15 nodes . The International Union Against Cancer (UICC) and AJCC have proposed that at least sixlymph nodes should be removed during resection of EC. Hu et al.  used a cutoff of six removed lymph nodesas the definition of adequate nodal dissection. Their results showed that patients with six or more lymph nodes dissected had a higher rate of positive lymph nodes identified (46.9% vs 30.3%) and an improvement in overall survival that was statistically significant in pathologically node-negative patients. Accordingly, we excluded patients who had fewer than sixdissected lymph nodes (range: 6 to 61). In our study, we did not find any survival rate difference when using a cutoff of 18 nodes (42.6% vs 44.7%, P = 0.741).
In the present study, the correlation related to MLMR was determined. As expected, we found that there was a positive correlation between MLNR and NMLN (r = 0.914, P < 0.001). There was a negative correlation between MLNR and TLN; however, the correlationwas not significant (r = −0.140, P = 0.110). ROC curves were plotted to verify the accuracy of MLNR staging and N staging for survival prediction. The AUCs were 0.731 for the 2010 AJCC N staging and 0.737 for the MLNR staging, indicating that the MLNR staging was similar to the AJCC Seventh Edition N staging system and could be used as an alternative prognostic staging tool for EC patients.
The potential limitations of the present study include the relatively small number of patients, the use of a retrospective analysis and the short duration of the mean follow-up. In addition, because the study used data from a single institution but with different pathologists and different surgeons, there may have been a lack of uniformity in measurement methods. Furthermore, owing to the limited number of patients in EC, our analysis may contain type I or type II errors. The results of the study should therefore be regarded with caution. Further studies are needed to explore its long-term effect.