Involved-Field Irradiation Versus Elective Nodal Irradiation in Patients With Locally Advanced Esophageal Squamous Cell Carcinoma Treated With Neoadjuvant Chemoradiotherapy.

BACKGROUND: The method of lymph node (LN) irradiation for locally advanced esophageal squamous cell carcinoma (LA-ESCC) is still a topic of debate. We investigated the efficacy, toxicity, and rate of out-of-field LNs in irradiation across different target areas in patients with LA-ESCC undergoing neoadjuvant chemoradiotherapy (nCRT). METHODS: We retrospectively reviewed patient records from June 2017 to August 2022 and divided patients into elective nodal irradiation (ENI) and involved-field irradiation (IFI) groups. The differences in hematological and non-hematological toxicities of the out-of-field LNs were analyzed between the two groups. The log-rank test was used to evaluate the Kaplan-Meier curves for overall and progression-free survival. RESULTS: Among the 306 included patients, 202 (66.0%) received ENI and 104 (34.0%) received IFI. At the 3-year follow-up, the survival rate did not differ significantly between the groups (p > 0.05). Although the occurrence of radiation-induced pneumonia did not differ (p > 0.05), the incidence of radiation-induced esophagitis and the degree of leukopenia differed significantly (p < 0.05). While the average heart irradiation dose or heart V20, V30, and V40 did not differ significantly (p > 0.05), we observed significant differences in the clinical target volume, average lung irradiation dose, and lung V20, V30, and V40 (p < 0.05). Among all patients, 29 cases (9.5%) experienced out-of-field LNs with 26 (93.1%) in abdominal LNs, whereas only 3 cases (6.9%) with out-of-field LNs were in the upper esophagus. There was no statistical significance between out-of-field LNs and LN irradiation methods (p = 0.724). CONCLUSIONS: Under similar prognostic conditions, IFI resulted in mild toxicity compared to ENI. Therefore, for patients with ESCC undergoing nCRT, IFI is the preferred irradiation approach for the lymphatic drainage area.