Early diagnosis of peritoneal metastases in patients with colorectal cancer (CRC) can influence patient prognosis. The aim of this study was to identify the clinical significance of carcinoembryonic antigen (CEA) in peritoneal fluid detected during operation in stage I–III CRC patients.

Between April 2009 and April 2015, we reviewed medical records from a total of 60 stage I–III CRC patients who had peritoneal fluid collected during operation. Patients who had positive cytology in the assessment of peritoneal fluid were excluded. We evaluated the values of CEA in peritoneal fluid (pCEA) to predict the long-term outcomes of these patients using Kaplan-Meier curves and Cox regression models.

The median follow-up duration was 37 months (interquartile range, 21–50 months). On receiver operating characteristic analysis, pCEA had the largest area under the curve (0.793; 95% confidence interval, 0.635–0.950; P=0.001) with an optimal cutoff value of 26.84 (sensitivity, 80.0%; specificity, 76.6%) for predicting recurrence. The recurrence rate was 8.1% in patients with low pCEA (<26.84 ng/mL, n=37), and 52.2% in patients with high pCEA (≥26.84 ng/mL, n=23). In multivariate Cox regression analysis, high pCEA (≥26.84 ng/mL) was a risk factor for poor cancer-free survival (CFS) in stage I–III patients.

In this study, we determined that high pCEA (≥26.84 ng/mL) detected during operation was helpful for the prediction of poor CFS in patients with stage I–III CRC.