Clinical significance of preoperative serum sialic acid levels in colorectal cancer: utility in the detection of patients at high risk of tumor recurrence.

This study was conducted to evaluate the significance of preoperative serum sialic acid levels in the diagnosis and prognosis of colorectal cancer (CRC). Total sialic acid (TSA) was determined by the thiobarbituric acid method and normalized to total protein (TP). A postoperative follow-up of CRC patients classified as Dukes' stages A, B or C was performed and survival analysis was carried out to evaluate the impact of sialic acid levels on tumor recurrence. Our diagnostic studies indicate that TSA/TP is a better marker than either TSA or carcinoembryonic antigen (CEA), especially for the detection of CRC patients at an early stage. At a cutoff of 30.90 nmol/mg of protein, TSA/TP showed a sensitivity of 85% with a specificity of 97% to discriminate CRC patients from healthy donors. In survival analysis, both TSA and TSA/TP were found to be significant prognostic factors for tumor recurrence in CRC. Furthermore, TSA/TP could distinguish patients at high risk of recurrence within Dukes' stage B and in multivariate analysis it was identified as the best independent prognostic factor. According to our results, preoperative serum TSA/TP content could supply additional information to that provided by Dukes' stage about the prognosis of CRC patients.