Identification of risk factors and the pattern of lower cervical lymph node metastasis in esophageal cancer: implications for radiotherapy target delineation

Radiotherapy remains the important therapeutic strategy for patients with esophageal cancer (EC). At present, there is no uniform opinion or standard care on the range of radiotherapy in the treatment of EC patients. This study aimed to investigate the risk factors associated with lower cervical lymph node metastasis (LNM) and to explore the distribution pattern of lower cervical metastatic lymph nodes. It could provide useful information regarding accurate target volume delineation for EC. We identified 239 patients who initial diagnosed with esophageal squamous cell carcinoma. The clinicopathological factors related to LNM were analyzed and the locations of the lower cervical metastatic lymph nodes were transferred onto computed tomography images. The lower cervical area was further divided into four subgroups areas. The results showed that the incidence of lower cervical LNM was 37.2 % (89 of 239) and 94.4 % (84 of 89 patients) patients had subgroup II and/or subgroup III region LNM. Of those patients, 151 nodes were considered to be clinical metastatic in the lower cervical region and 96% nodes were located in group II and group III. Based on the present study, prophylactic irradiating to lower cervical areas is recommended for patients with deeper tumor invasion, the mediastinal level 1, 2, and 4 station LNM and the more number of LNM. The atlas showed that, for the lower cervical area, the subgroup II and III region should be precisely covered in the target volume and the subgroup I and IV may be spared for minimizing the toxicity.