Cell-free DNA as a biomarker for colorectal cancer: a retrospective analysis in patients before and after surgery

This study was aimed at investigating the potential of cell-free DNA (cfDNA) as a biomarker for colorectal cancer prognosis. Sixty patients with colorectal cancer who had not undergone surgery were enrolled as study group. Their peripheral blood samples were collected, and peripheral blood of 30 healthy volunteers (control) was collected. The cfDNA concentration and integrity were determined using q-PCR so as to ascertain if cfDNA was associated with clinical presentations of the disease. Then, the specificities and sensitivities of cfDNA, CFA and CA199 were determined with ROC curve. The level and integrity of cfDNA in patients with colorectal cancer before surgery were significantly higher than those in patients with colorectal cancer after surgery, and cfDNA concentration of colorectal cancer patients after surgery was also significantly higher than that in healthy control group. However, the integrity was not significantly different from that of control group. There was a significant correlation between cfDNA concentration and TNM stage, differentiation degree and CEA expression, while cfDNA integrity was significantly correlated with TNM stage and degree of differentiation. Moreover, specificity and sensitivity of cfDNA concentration and integrity were higher than those of CEA and CA199. The TNM stage and cfDNA concentration were independent risk factors for progression-free survival (PFS) in colorectal cancer patients. In conclusion, cfDNA concentration and integrity were more sensitive and specific than traditional tumor markers (CA199, CEA). Thus, changes in cfDNA changes can be effectively used to determine the prognosis of postoperative colorectal cancer patients.