Involved-Field Irradiation in Definitive Chemoradiotherapy for Locoregional Esophageal Squamous Cell Carcinoma: Results From the ESO-Shanghai 1 Trial

Purpose To evaluate the feasibility and efficacy of involved-field irradiation in definitive chemoradiation therapy for locoregional esophageal squamous cell carcinoma. Methods and Materials Patterns in recurrence and elective nodal failure were analyzed in patients from the previously published ESO-Shanghai 1 trial, who received definitive chemoradiation therapy with involved-field irradiation to 61.2 Gy in 34 fractions using intensity modulated radiation therapy planning. Nodal regions were delineated using the lymph node map from the sixth edition of the American Joint Committee on Cancer staging system. Elective nodal failure was defined as recurrence in the regional nodal area outside the planning target volume. Extensive elective nodal failure, defined as an extensive nodal area regardless of tumor location, was calculated for additional analysis. The incidental (ie, mean) irradiation dose of each node and each region was evaluated. Results With a median follow-up of 48.7 months among survivors, the 3-year actuarial rate for overall survival was 53.6%, and the median overall survival was 44.8 months (95% confidence interval, 34.6-55.0). Of the 436 patients included in this study, 258 patients (59.2%) experienced treatment failure. Elective nodal failure was experienced by 37 patients (8.5%), 7 (1.6%) of whom encountered nodal-only failure. The 3-year actuarial rates of elective nodal control and elective nodal-only control were 89.7% and 97.9%, respectively. The median incidental dose of these nodes was 33.2 Gy (interquartile range [IQR], 1.3-50.7 Gy). The median distance of each node to the planning target volume was 1.4 cm (IQR, 0.6-4.9 cm). Extensive elective nodal failure was experienced by 51 patients (11.6%), and 20 (4.6%) patients had nodal-only failure. The 3-year extensive elective nodal control and extensive elective nodal control-only rates were 86.0% and 94.3%, respectively. The median incidental dose of these nodes was 23.2 Gy (IQR, 1.1-53.5 Gy). The median distance of each node to the planning target volume was 2.0 cm (IQR, 0.6-5.5 cm). Conclusion Involved-field irradiation can achieve a low rate of isolated nodal failure and a satisfactory survival outcome. The use of elective nodal irradiation may be unnecessary in definitive chemoradiation therapy for the treatment of locoregional esophageal squamous cell carcinoma.