Application Of CtDNA Detection In Diagnosis And Treatment Of Colorectal Cancer Based On Next Generation Sequencing

Objective: To explore the feasibility and application of Circulating-tumor DNA(ct DNA)in the diagnosis and treatment of colorectal cancer by using Next Generation Sequencing(NGS).Methods: 20 patients of department of Gastrointestinal Surgery,Shenzhen People 's Hospital who suffered from colorectal cancer were collected,from August 2016 to January 2017.Tumor tissue and peripheral blood 3 days before surgery and 21 days after surgery were obtained from these 20 patients.The tumor tissue DNA and circulating free DNA was extracted,and detected by NGS.The ct DNA sequencing data were analyzed by comparing with histological DNA sequencing data,immunohistochemistry(IHC)test results and conventional tumor marker carcinoembryonic antigen(CEA).Result: The total amount of cf DNA in 20 patients was higher than that in the first 3 days(Z =2.278,P = 0.023).While preoperative cf DNA(X~2=0.460,P=0.928)and postoperative cf DNA(c 2=2.512,P=0.473)were not statistically significant respectively in patients with different stages.The sensitivity,specificity and correct rate were 100% that mutation of tumor-associated genes detected by NGS and IHC.And the sensitivity,specificity and correct rate were 75.0%,100% and 90.0% respectively,that mutation of tumor-associated genes of tumor tissue and preoperative ct DNA were detected by NGS.The ct DNA mutation rate(Z = 2.793,P = 0.005)and positive rate(X~2=6.667,P=0.010)were lower than that before operation.The positive rate of ct DNA in peripheral blood was higher than that in CEA(X~2=10.101,P=0.001),and there was a significant statistical difference between ct DNA and CEA positive negative rate in peripheral blood(P = 0.023).While there was no significant statistical difference in CEA(Z = 1.680,P =0.093)and CEA positive rate(X~2=0.125,P=0.723).Conclusion: The results of ct DNA detection of patients with colorectal cancer based on next generation sequencing were highly consistent with the results of tumor tissue test,and ct DNA can be detected when the tumor tissue is not available for gene sequencing.Colorectal cancer cf DNA is more sensitive than CEA in assessing tumor burden,thus cf DNA is expected to be used as a new tumor marker in colorectal cancer for real-time monitoring of disease development.