Objective: To investigate the log odds of positive lymph nodes(LODDS) on the prognosis of patients with node-negative squamous cell carcinoma of the thoracic esophagus after radical esophagectomy.
Methods: Clinical data of 136 patients with node-negative squamous cell carcinoma of the thoracic esophagus after radical esophagectomy from January 2005 to January 2009 were retrospectively analyzed. LODDS was estimated using the calculation: log(pnod+0.5)/(tnod-pnod+0.5), in which pnod indicates the number of positive lymph nodes and tnod indicates the total number of lymph nodes retrieved. The best cut-off value for LODDS was identified by using the receiver operating characteristic (ROC) curve. Drawing of survival curves was employed with the Kaplan-Meier estimator, and survival rate was analyzed using Log-rank test. The Cox proportional hazard model was used to identify independent factors associated with prognosis.
Results: A total of 136 patients, including 112 males and 24 females, seventy-nine patients were 65 years or older(range 27-92 years), and were included in the present study. Among them, the most cancer site was the middle third of the thoracic esophagus(115 cases), followed by the lower third(13 cases), and the upper third(8 cases). There were 70 patients with tumor diameter ≤3.5 cm and 66 patients with tumor diameter >3.5 cm. There were 32 patients with stage pT1-2, and 104 with stage pT3-4. The number of patients in TNM classification I, II and III was 14, 85 and 37, respectively. All the patients received radical esophagectomy with primary tumor resection and lymph node dissection. The median follow-up time was 44.2 months(range, 4.4-98.4 months). Five-year overall survival rate was 43.2%, and the median total survival time was 48 months. ROC analysis showed that the appropriate cut-off value of LODDS was -1.2. There were 99 patients with LODDS≤-1.2(LODDS1 stage), 37 patients with LODDS >-1.2(LODDS2 stage), the median survival time and 5-year survival rate were 56.5 months and 48.3% in patients with LODDS1 stage and 30.0 months and 29.7% in patients with LODDS 2 stage, respectively, with significant difference(χ(2)=4.980, P=0.026). Multivariate analyses showed that recurrence(HR=0.627, 95% CI:0.395 to 0.996; P=0.048) and LODDS >-1.2(HR=1.853; 95% CI:1.155 to 2.974; P=0.011) were the independent factors affecting the prognosis of patients.
Conclusions: For patients with node-negative squamous cell carcinoma of the thoracic esophagus after radical esophagectomy, LODDS stage has a unique prediction for prognosis, and patients with LODDS less than -1.2 (cut-off value) have a better prognosis.