Background: The American Joint Committee on Cancer-Tumor (AJCC-T) staging

system for esophageal carcinoma patients, which is based on the depth of tumor

invasion, is not applicable in some cases. This study aims to assess the prognostic

value of CT imaging-based tumor volume and its usefulness for T staging in patients with

non-surgical esophageal squamous cell carcinoma (ESCC).

Methods: We retrospectively reviewed the records of 158 ESCC patients undergoing

defifinitive (chemo) radiotherapy from two hospitals. Tumor volume based on the CT

imaging was calculated using the formula: V = pabc / 6. Three cutoff points for tumor

volume were obtained with the X-tile software. Overall survival (OS) was analyzed using

the Kaplan–Meier method. The -2 log-likelihood ratio and Akaike Information Criterion

(AIC) value were evaluated to compare the AJCC-T staging system with the proposed T staging method.

Results: The median tumor volume was 19.8 cm³ (range from 1.0 to 319.5 cm³). The

three optimal cutoff points of tumor volume were 12.7, 22.8, and 51.9 cm³, and the

patients were divided into four groups named as proposed T1–T4 stages. The 3-year OS rates in patients with proposed T1 to T4 stages were 67.9%, 30.6%, 21.3%, and 5.3%,respectively. The −2 log-likelihood ratios of the AJCC-T stage and proposed T stage were 1,068.060 and 1,047.418, respectively. The difference in the AIC value between the two T staging systems was 18.642.

Conclusion: CT imaging-based tumor volume was superior to the depth of tumor

invasion for T staging in predicting the prognosis of non-surgical ESCC patient.