Highly sensitive diagnostic method for colorectal cancer using the ratio of free DNA fragments in serum

OBJECTIVES: The correlations of the ratio of long-/short-chain DNA fragments in blood with the existence of cancer and the clinicopathological features of colorectal cancer (CRC) were examined. The potential use of this ratio for diagnostic screening was evaluated. METHODS: DNA concentrations were amplified using Alu247 for long-chain DNA fragments and Alu115 for long- and short-chain DNA fragments. The Alu247/115 ratio was calculated for 60 patients with CRC and 24 healthy volunteers. The correlation of the Alu247/115 ratio with clinicopathological variables and the efficacy of this ratio as a tumor marker were examined. The Alu247/115 ratio cut-off value was set using a receiver operating characteristic (ROC) curve. RESULTS: The Alu247/115 ratio was significantly higher in patients with CRC than in healthy volunteers (P<0.001). The Alu247/115 ratio was also significantly higher in patients with Dukes stage A or B CRC than in healthy volunteers (P=0.034) as well as in patients with Dukes C or D CRC than in those with Dukes A or B CRC (P=0.016). Among patients with CRC, the Alu247/115 ratio was significantly higher in those with than without venous invasion (P=0.031). Using the cut-off value set from the ROC curve, the sensitivity of the Alu247/115 ratio was significantly higher than that of the carcinoembryonic antigen level (P=0.004) or the carbohydrate antigen 19-9 level (P<0.001). CONCLUSION: Our data suggest that the Alu247/115 ratio is a promising tool for highly sensitive and early detection of CRC.