Pattern of subcarinal lymph node metastasis and dissection strategy for thoracic esophageal cancer

BACKGROUND: This study aimed to assess the role of subcarinal lymph nodes in lymph node metastasis in thoracic esophageal squamous cell carcinoma (ESCC) and to investigate the adequate range of lymph node dissection during esophagectomy. METHODS: This study included 782 thoracic ESCC patients who underwent esophagectomy between July 2008 and December 2010. The metastatic rate of subcarinal lymph nodes and their influencing factors were investigated. The outcome of subcarinal lymph node dissection was assessed using the efficacy index (the incidence of metastasis to a lymph node station (%) multiplied by the 5-year survival rate (%) of patients with metastasis to that lymph node station and divided by 100). Additionally, postoperative complications were compared between the subcarinal lymph node resection and reservation groups. RESULTS: The metastatic rates of subcarinal lymph nodes in the upper, middle, and lower thoracic ESCC were 8.3% (4/48), 19.1% (79/414), and 16.2% (23/142), respectively (χ(2)=3.669, P>0.05) and in T1, T2, T3, and T4 tumors were 0% (0/71), 4% (4/100), 22.2% (85/383), and 34% (17/50), respectively (χ(2)=42.859, P<0.05). Tumor invasion and size were significantly correlated with metastasis. For upper thoracic ESCC with positive subcarinal lymph nodes, metastasis tendency was mainly to the lower mediastinum. In middle third esophageal cancer, after subcarinal lymph nodes were involved, metastasis to the lower mediastinal lymph nodes increased by nearly 50%, and bidirectional metastasis increased by nearly three times compared with that before involvement. For lower third cancer with positive subcarinal lymph nodes, metastasis tendency was mainly to the upper mediastinum. The postoperative complication rates in the resection and reservation groups were as follows: overall, 19% and 14.6%, respectively (P>0.05), and pulmonary, 10.3% and 7.3%, respectively (P>0.05). The efficacy indexes of lymph node dissection at the upper, middle, and lower third esophagus were 0%, 7.6%, and 27.5%, respectively. CONCLUSIONS: Dissection of subcarinal lymph nodes, which does not increase postoperative complications, should be performed routinely in lower thoracic ESCC after submucosal invasion of tumor; meanwhile, tumors larger than 3cm should also result in subcarinal lymph node dissection in patients with a tumor located in the upper esophagus and T1-T2 ESCC.