Alu-based cell-free DNA: a potential complementary biomarker for diagnosis of colorectal cancer.

Many patients with colorectal cancer (CRC) present with regional or widespread metastasis, partially reflecting limitations of the current screening programs. This study was aimed to find a complementary marker that can improve the diagnostic accuracy. Concentrations of cell-free DNA based on Alu (Alu-based CFD) in 31 unselected CRC patients, 30 intestinal polyp patients and 92 healthy individuals were detected by branch DNA (bDNA). Concentrations of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) were detected by ARCHITECT assay. There was significant difference in concentrations of CFD between CRC and intestinal polyp patients or healthy individuals (P<0.0001). There was no statistically significant difference in CFD in different subgroups of CRC patients with respect to gender, age, tumor site and pathologic stage, suggesting that CFD might be an independent marker relative to CEA and CA19-9. There was a significant correlation between pathologic stage and CEA or CA19-9. Although no significant correlation was observed between pathologic stage and CFD, CFD (the area under the receiver operating characteristic curve (AUC)=0.904) seemed to be a better indicator to distinguish CRC patients from intestinal polyp patients as compared with CEA (AUC=0.681) or CA19-9 (AUC=0.651). CFD was more accurate than CEA or CA19-9 in diagnosing CRC. Combination of CFD, CEA and CA19-9 may be a better option for the diagnosis of CRC than any of them used alone. Discrimination CRC from intestinal polyp patients with CFD and staging with CEA and CA19-9 may substantially improve the accuracy CRC diagnosis.