P-196 CA 19-9 and CEA as markers of survival in rectal cancer

Carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) are recognized biomarkers for disease monitoring in rectal cancer. The aim of the present study was to evaluate the value of pre-radiotherapy serum CA19-9 and CEA levels for the prediction of disease-specific survival (DSS) and overall survival (OS) in rectal cancer treated with curative intent. A retrospective observational study of 268 patients with a diagnosis of rectal cancer treated with curative intent at the Department of Radiotherapy between 2013 to 2017 was conducted. The optimal CA19-9 cut-off values for the prediction of DSS and OS were identified by receiver operating characteristic (ROC) curve analysis according to the highest Youden index using MedCal software, version 19.1.7. The other data were analysed through IBM SPSS statistics software, version 26.0. Differences in DSS and OS rates stratified by CA19-9 and CEA levels were compared by using Kaplan–Meier and log-rank tests. Cox proportional hazards model was used to identify prognostic variables for DSS and OS. Patients were followed up for a mean time of 33 months (SD: 19.3), and the mean age at diagnosis was 63.9 years (SD: 11.96). According to ROC analysis, the optimal CA19-9 cut-off value for 5-year OS was 12 U/ml, with the highest Youden index (0.2545), a sensitivity of 54.90% and a specificity of 70.55% (area under the ROC curve [AUC], 0.652; 95% CI, 0.581-0.718; p= 0.001). The optimal CA19-9 cut-off value for 5-year DSS was 12, with the highest Youden index (0.3006), a sensitivity of 60% and a specificity of 70.06% (AUC, 0.685; 95% CI, 0.615-0.749; p= 0.0002). Thus, patients were divided into the high-CA19-9 group (n=71, 26.5%) and the low-CA19-9 group (n=126, 47%) based on the CA19-9 cut-off value of 12 U/ml. According to ROC analysis, the optimal CEA cut-off value for 5-year OS was 8.3 ng/ml, with the highest Youden index (0.1966), a sensitivity of 41.54% and a specificity of 78.12% (area under the ROC curve [AUC], 0.618; 95% CI, 0.555-0.677; p= 0.003). The optimal CEA cut-off value for 5-year DSS was 8.3 ng/ml, with the highest Youden index (0.1543), a sensitivity of 39.22% and a specificity of 76.21% (AUC, 0.587; 95% CI, 0.524-0.648; p= 0.049). Thus, patients were divided into the high-CEA group (n=69, 25.7%) and the low-CEA group (n=188, 70.1%) based on the CEA cut-off value of 8.3 ng/ml. The univariate analysis revealed that high CA19-9 level (p=0.001) and high CEA level (p=0.007), were the significant negative predictors of DSS. In OS, high CA19-9 level (p=0.002) and high CEA level (p=0.001), were the significant negative predictors. Multivariate analyses revealed that CA19-9 was an independent factor associated with DSS (hazard ratio [HR], 2.108; 95% CI, 1.040-4.273; p=0.039). The results of this study showed that high levels of pre-radiotherapy serum CA19-9 (>12 U/ml) indicated a worse DSS for rectal cancer treated with curative intent.