The value of plasma SEPT9 gene methylation combined with serum carcinoembryonic antigen and carbohydrate antigen 724 in the diagnosis of colorectal cancer / 肿瘤研究与临床

ABSTRACT

Objective:To investigate the clinical application value of plasma SEPT9 gene methylation combined with serum carcinoembryonic antigen (CEA) and carbohydrate antigen 724 (CA724) in the diagnosis of colorectal cancer.Methods:A total of 219 patients with colorectal diseases in Baoji Central Hospital and Yunnan Province New Kun Hua Hospital from May 2018 to October 2021 were selected, including 149 cases of colorectal cancer and 70 cases of colorectal polyp diagnosed by pathology. A total of 100 healthy people in the same period were selected as the healthy control group. The methylation of SEPT9 gene in plasma was measured by using real-time fluorescent polymerase chain reaction (PCR), and the levels of serum CEA and CA724 were measured by using electrochemiluminescence. The expressions of three indicators in each group were compared, and the effect of every single indicator and the combination of the three indicators on the diagnosis of colorectal cancer was analyzed by using receiver operating characteristic (ROC) curve.Results:The positive rate of SEPT9 gene methylation in colorectal cancer group (74.50%, 111/149) was higher than that in colorectal polyp group (22.86%, 16/70) and healthy control group (1.00%, 1/100), and the difference was statistically significant ( P < 0.001). The positive rate of CEA in colorectal cancer group (46.98%, 70/149) was higher than that in colorectal polyp group (40.00%, 28/70) and the healthy control group (3.00%, 3/100) and the difference was statistically significant ( P < 0.001). The positive rate of CA724 in colorectal cancer group (38.93%, 58/149) was higher than that in colorectal polyp group (32.86%, 23/70) and the healthy control group (2.00%, 2/100), and the difference was statistically significant ( P < 0.001). The area under the curve (AUC) of ROC of SEPT9 gene methylation, CEA and CA724 in the single diagnosis of colorectal cancer was 0.823 (95% CI 0.753-0.891), 0.788 (95% CI 0.725-0.852) and 0.689 (95% CI 0.624-0.754), respectively. The optimal cut-off Ct value of SEPT9 gene methylation in the diagnosis of colorectal cancer was 36.5, the sensitivity was 90.30%, and the positive predictive value was 84.68%, which were higher than those of CEA and CA724. The optimal cut-off value of CEA in the diagnosis of colorectal cancer was 8.80 ng/ml, and the specificity (77.50%) and negative predictive value (78.48%) were higher than those of SEPT9 gene methylation and CA724. The sensitivity (97.66%), positive predictive value (93.98%), negative predictive value (81.25%) and AUC (0.846, 95% CI 0.749-0.944) of the combined detection of the three indexes taking the optimal cut-off value of every single indicator were higher than those of the single indicator. Conclusions:The combined detection of plasma SEPT9 gene methylation, CEA and CA724 in the diagnosis of colorectal cancer has high sensitivity and accuracy. The three combined detection can complement each other and improve the diagnostic efficiency, which is of high clinical value for the diagnosis of colorectal cancer.