Prognostic value of the ratio of pretreatment carcinoembryonic antigen to tumor volume in rectal cancer

Abstract

Background As a commonly used biomarker in rectal cancer (RC), the prognostic value of carcinoembryonic antigen (CEA) remains underexplored. This study aims to evaluate the prognostic value of pretreatment CEA/tumor volume in RC. Methods This retrospective study included patients who underwent pretreatment magnetic resonance imaging (MRI) with histologically confirmed primary rectal adenocarcinoma from November 2012 to April 2018. Patients were divided into high-risk and low-risk groups according to the median values of CEA/Dia path (CEA to pathological diameter), CEA/Dia MRI (CEA to MRI tumor diameter), and CEA/Vol MRI (CEA to MRI tumor volume). Cox regression analysis was utilized to determine the prognostic value of CEA, CEA/Dia path , CEA/Dia MRI , and CEA/Vol MRI . Stepwise regression was used to establish nomograms for predicting disease-free survival (DFS) and overall survival (OS). Predictive performance was estimated by using the concordance index (C-index) and area under curve receiver operating characteristic (AUC). Results A total of 343 patients [median age 58.99 years, 206 (60.06%) males] were included. After adjusting for patient-related and tumor-related factors, CEA/Vol MRI was superior to CEA, CEA/Dia path , and CEA/Dia MRI in distinguishing high-risk from low-risk patients in terms of DFS [hazard ratio (HR) =1.83; P=0.010] and OS (HR =1.67; P=0.048). Subanalysis revealed that CEA/Vol MRI stratified high death risk in CEA-negative individuals (HR =2.50; P=0.038), and also stratified low recurrence risk in CEA-positive individuals (HR =2.06; P=0.024). In the subanalysis of stage II or III cases, the highest HRs and the smallest P values were observed in distinguishing high-risk from low-risk patients according to CEA/Vol MRI in terms of DFS (HR =2.44; P=0.046 or HR =2.41; P=0.001) and OS (HR =1.96; P=0.130 or HR =2.22; P=0.008). The nomograms incorporating CEA/Vol MRI showed good performance, with a C-index of 0.72 [95% confidence interval (CI): 0.68–0.79] for DFS and 0.73 (95% CI: 0.68–0.80) for OS. Conclusions Higher CEA/Vol MRI was associated with worse DFS and OS. CEA/Vol MRI was superior to CEA, CEA/Dia path , and CEA/Dia MRI in predicting DFS and OS. Pretreatment CEA/Vol MRI may facilitate risk stratification and treatment decision-making.