A Comparative Study On The Detection Of MSI In Gastrointestinal Neoplasms By NGS Method And PCR Method

Objectives:The consistency of NGS(second generation sequencing)method and PCR method for detecting MS(Microsatellite)in tumor tissue was compared,and the consistency of NGS method for detecting MSI in tumor tissue and blood samples was compared.Methods:From March 2019 to December 2019,41 patients with colorectal cancer or gastric cancer in the Oncology Department of the first affiliated Hospital of Kunming Medical University were collected and detected by PCR method and NGS method to compare the consistency of the two methods.For the patients with MSI-H detected by PCR method,their plasma was collected,ctDNA was extracted to detect MSI status,and the consistency of NGS in tissue and MS in blood was evaluated.Results:A total of 41 patients with tumor samples were collected in this project,of which 36 were colorectal cancer(88%)and 5 were gastric cancer(12%);20 were male and 21 were female,with an average age of(60±14)years.Of the 41 patients,24 were diagnosed as MSI-H by standard detection method PCR.The clinical characteristics of the 24 patients with MSI-H were as follows:more female(58%),the average age was 59.6 years old,the right colon was mostly(33%),and the rectum(8%)was relatively infrequent in the early stage of MSI-H;(0 to 71%of ? stage).The tissue samples of 41 patients were detected by NGS method and MSI,could be accurately detected in 40 cases.Compared with PCR method,NGS method showed better detection performance.Sensitivity(SN)96%,specificity(SP)100%,accuracy(ACC)98%,positive predictive value(PPV)100%,negative predictive value(NPV)94%dagger Kappa coefficient 0.950(p>0.05).24 patients with MSI-H detected by PCR method received NGS method to detect MSI in matched blood,Among the 24 cases,5 cases were detected,the detection rate was 20.8%,the detection rate was not ideal.Sensitivity(SN)22%,specificity(SP)100%,accuracy(ACC)25%.Kappa coefficient 0.023(p<0.05)Conclusions:There is a good consistency between tissue MSI status measured by NGS method and tissue MSI status measured by PCR method,which may be used as an alternative method of PCR in clinic.Although the detection rate of MSI status by ctDNA based on NGS is low,it is still possible to become a feasible clinical detection method to benefit patients who are unable to obtain tumor tissue.