Impact of number and extent of lymph node metastasis on prognosis of thoracic esophageal cancer

Abstract

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. 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. 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. 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.