Significance of intratreatment tumor volume change during chemoradiotherapy for potentially resectable thoracic esophageal squamous cell carcinoma

Objective: The purpose of this study was to investigate the clinical significance of tumor response assessment at a twentieth fraction of radiotherapy when predicting the survival of patients with potentially resectable esophageal squamous cell carcinoma (ESCC).

Methods: A total of 123 ESCC patients with clinical stages II to IV_a were enrolled and analyzed. Gross tumor volume (GTV) of the esophagus (GTV_e) and GTV of the metastatic lymph node (GTV_nd) were manually contoured by at least 2 senior professional radiotherapists on the simulated computed tomography (CT) images in a process that followed the delineating rules for ESCC.

Results: The GTV_e reduction ratio (RR) and GTV_nd RR were calculated based on the evaluation of the tumor volume at a twentieth fraction of radiotherapy. Univariate analysis showed that GTV_e and GTV_nd before treatment, and GTV_e RR and GTV_nd RR at the twentieth fraction of radiotherapy were all significantly associated with complete clinical response (cCR) and overall survival (OS). The Kaplan-Meier method was used to estimate OS and locoregional recurrence-free survival (LRRFS).

Conclusions: The GTV_e RR ≥27.92% and GTV_nd RR ≥21.49% at a twentieth fraction of radiotherapy are positive predictive factors of LRRFS, and according to multivariate analysis, only GTV_e RR at the twentieth fraction of radiotherapy ≥27.92% is prognostic for a favorable OS.