Lymph Node Status after Neoadjuvant Chemoradiation Therapy for Esophageal Cancer according to Radiation Field Coverage

BACKGROUND: To explore the effect of radiation on metastatic lymph nodes (LNs) after neoadjuvant chemoradiation therapy (nCRT), we examined the metastatic features of LNs according to their inclusion in the radiation field. METHODS: The patient group included 88 men and 2 women, with a mean age of 61.1±8.1 years, who underwent esophagectomy and lymphadenectomy after nCRT. Dissected LNs were compared in terms of clinical suspicion of metastasis, nodal station, and inclusion in the radiation field. RESULTS: LN positivity did not differ between LNs that were inside (in-field [IF]) and outside (out-field [OF]) of the radiation field (IF: 40 of 465 [9%], OF: 40 of 420 [10%]; p=0.313). In clinical N+ nodal stations, IF stations had a lower incidence of metastasis than OF stations (IF/cN+: 16 of 142 [11%], OF/cN+: 9/30 [30%]; p=0.010). However, in clinical N- nodal stations, pathological positivity was not affected by whether the nodal stations were included in the radiation field (IF/cN-: 24 of 323 [7%], OF/cN-: 31 of 390 [8%]; p=0.447). CONCLUSION: Radiation therapy for nCRT could downstage clinically suspected nodal metastasis. However, such therapy was ineffective when used to treat nodes that were not suspicious for metastasis. Because significant numbers of residual metastases were identified irrespective of coverage by the radiation field, lymphadenectomy should be performed to ensure complete removal of residual nodal metastases after nCRT.