Pathological analysis of extracapsular extension of metastatic lymph node and its potential impact on nodal clinical target volume in the radiotherapy of esophageal squamous cell carcinoma

There is no consensus regarding the clinical target volume (CTV) margins which surround the gross tumor volume of metastatic lymph nodes (LN) in radiotherapy of esophageal squamous cell carcinoma (ESCC). This study retrospectively assessed the distance of extracapsular extension (ECE) of metastatic LN in thoracic ESCC and defined nodal CTV margins. Histological sections of metastatic LNs from 217 patients with thoracic ESCC were re-examined. The incidence and maximal distance of ECE of metastatic LNs were assessed. The relationships between ECE and clinicopathologic features were also investigated. The ECE was found in 37.3% of patients (81/217) and 23.1% of metastatic LN (159/689), and the incidences had a significant relationship with N stage and LN size. The median distance of ECE was 1.0 mm (range, 0.2-9.7 mm). The distance of ECE showed a positive correlation with LN size (Spearman's correlation coefficient = 0.419; p