Objective: To evaluate the influence of the number, station and field of metastatic lymph node on the prognosis of thoracic esophageal cancer and to investigate an ideal nodal staging method.
Methods: Clinicopathological and follow-up data of the 204 patients who underwent thoracic esophagectomy from June 2001 to December 2009 were analyzed retrospectively and all the patients were re-staged according to the 7th edition of the AJCC TNM staging system. Log-rank test was applied to perform survival analysis according to lymph node metastasis staging(number, station, and field), Cox proportional hazard model was used to screen risk factors.
Results: The follow-up rate was 93.1%(190/204). The median follow up time was 37.0(0-104) months. The overall and cancer-specific 5-year survival rates were 35.0% and 38.8%. When grouped according to the number of metastatic lymph node(0, 1-2, 3-6, ≥ 7), the 5-year survival rates of pN0, pN1, pN2 and pN3 were 47.8, 31.8%, 11.5% and 0 respectively(P=0.000). When grouped according to the number of stations of metastatic lymph node[N(0s), N(1s)(1 station LN metastasis), N(≥ 2s)(≥ 2 stations LN metastasis)], the 5-year survival rates of N(0s), N(1s), N(≥ 2s) were 47.8%, 31.5% and 11.3% respectively(P=0.000). When grouped according to the number of fields of metastatic lymph node, the 5-year survival rates of N0, 1 field, 2 fields and 3 fields involvement were 47.8%, 34.2%, 12.1% and 0 respectively(P=0.000). Cox regression showed that the number of stations [P=0.043, RR(95% CI)=1.540(1.013-2.342)], and the number of fields[P=0.010, RR(95%CI)=2.187(1.210-3.951)] of metastatic lymph node were the independent risk factors for survival.
Conclusions: The extent of metastatic lymph node is an independent risk factor for the prognosis of esophageal cancer patients. Revision of the current N-classification of TNM staging system according to the number of stations of metastatic lymph node may be more reasonable.