OBJECTIVETo evaluate the impact of total number of removed regional lymph nodes (LN) during esophagectomy on TNM staging and long-term survival.

METHODSBetween 1984 and 1989, a total of 1098 patients with advanced squamous cell carcinoma of the thoracic esophagus were surgically treated, and the data were retrospectively analyzed. The survival was analyzed by Kaplan-Meier method. Multivariate and univariate analysis were performed using Cox proportional hazard model and Log-rank test respectively in order to compare the survival difference and the impact of <6 or > or =6 removed LN on TNM staging and survival.

RESULTSThe shortest follow-up time was 10 years with a follow-up rate of 91.4%. Of these 1098 patients, 378 patients were found to have regional LN metastases with a LN metastasis rate of 34.4%. Totally, 4157 LN were removed and tumor spreading into the lymph node was documented in 800 with a lymph node metastasis degree of 19.2%. The mean number of removed LN in each esophgectomy was 3.8. According to the number of total removed LN, patients were divided into group A (removed LN <6, N=825) and group B (removed LN > or =6, N=273). The survival of group A was worse than that of group B. The depth of tumor invasion, degree of lymph node metastasis, tumor location, and tumor residual status were the most important prognostic factors. Even though the lymphatic metastasis rate in group A was significantly lower than that in group B (30.3% vs. 46.9% P < 0.001), the LN metastasis degree was higher in group A than that in group B (21.2% vs. 17.5% P = 0.002) due to less number of removed LN in group A than in group B. With the stratification analysis according to the number of involved lymph nodes, for patients without LN spreading, the survival in group A was significantly worse than that in group B (P = 0.003), but in the patients with only one or > or =2 positive nodes, the survival was similar (P = 0.919 and 0.182, respectively). When stratified patients according to TNM stage, for stage IIa patients (T2N0M0, T3N0M0), the survival in group A was significantly worse than that in group B (P = 0.006), while such difference did not exist in patients with stage IIb or stage lIII(P = 0.302 and 0.108, respectively).

CONCLUSIONA large series of retrospective study on advanced squamous cell carcinoma of the thoracic esophagus demonstrates that the number of metastatic LN is an important prognostic factor, therefore, it should be considered when refining UICC-TNM classification for esophageal cancer. If the total number of LN removed during each esophagectomy is less than 6, the occult positive regional LN might be missed, resulting in an inaccurate N classification and incorrect staging. Removal of > or = LN for each esophageal cancer patient during esophagectomy recommended by UICC is rational and should be complied with.