Implication of clinical target delineation for T1b/T2 thoracic esophageal squamous cell carcinoma based on the pattern of lymph node metastases

Aim: This study aimed to explore different patterns of lymph node metastases (LNM) in T1b and T2 thoracic esophageal squamous cell carcinoma (ESCC), and to further clarify its significance in radiotherapy target delineation. Materials & methods: Data of 1960 patients with T1b and T2 thoracic ESCC treated at different cancer centers were retrospectively analyzed. All patients underwent esophagectomy and lymphadenectomy chi(2) test and multivariate analysis were applied for analyzing clinicopathological factors related to LNM. Results: Age, location, tumor length, T stage and pathological grade were significantly associated with LNM (p < 0.01). For T1b ESCC, LNM rates in all sites were below 15%. For T2 upper thoracic ESCC, LNM rates were over 15% in upper mediastinal (15.8%). For T2 middle thoracic ESCC, LNM rates were middle mediastinal (17.2%) and abdominal (15.5%). For T2 lower thoracic ESCC, LNM rates were lower mediastinal (24.9%) and abdominal (22.5%). Subgroup analysis of T2 middle thoracic ESCC demonstrated that for patients older than 60 years, tumor length <4 cm and tumors were well differentiated. The LNM rates for abdominal were 11.9, 12.7 and 9.9%. Conclusion: Given the different patterns of LNM between T1b and T2 thoracic ESCC, target delineation should be adjusted accordingly.