Detection Of Plasma CtDNA-BRAF-V600E Mutation And CfDNA In Patients With Colorectal Cancer By Liquid Biopsy

Background and purposeAccording to the 2018 World Cancer Report,the incidence of colorectal cancer(CRC)is ranked fourth(6.1%)in all malignancies worldwide,and mortality ranks second among all malignancies(9.2%).[1]According to the latest Chinese cancer cause report,in 2015(China,s cancer data lags behind for 3 years),the number of new cancers in China was 3.929 million,and the death toll was 2.338 million.Among them,the incidence of colorectal malignant tumors in men rarked fourth among all malignant tumors.The incidence rate is ranked fifth among all malignant tumors;the incidence rate is the third among all malignant tumors in women,and the mortality rate ranks fourth among all malignant tumors.[90]Due to the special site of the disease early symptoms are not obvious and the disease screening method is not convenient.When the disease is diagnosed the Staging of disease is often advanced;and there is no simple and reliable diagnosis and monitoring method except image and colonoscopy.Due to the severe and complex tumor prevention and control situation in China,the establishment of a simple and highly manipulative screening method will greatly improve the detection rate of colorectal cancer,shorten the detection time and establish a dynamic observation system to achieve the progress of tumor monitoring.At present,studies have shown that cell free DNA(cfDNA)levels in tumor patients and high-risk populations are significantly higher than healthy people,and studies have shown that mutations in BRAF-V600E gene may adversely affect the treatment and prognosis of patients with colorectal cancer,so Detection of BRAF-V600E gene mutations in patients with colorectal cancer can improve the prognosis of patients while guiding patients to rational treatment.At present,conventional BRAF detection is based on specimens obtained from tissue biopsy,and tissue biopsy has defects such as invasive method and cannot fully reflect the patient's overall tumor heterogeneity,and cannot fully meet clinical needs.With the development of liquid biopsy technology,quantitative detection of cfDNA in a virtually non.invasive manner may be a potential screening tool for early diagnosis and high-risk populations of colorectal cancer,and detection of ctDNA components derived from tumors in cfDNA is expected be a Non-invasive and real-time method for the detection of BRAF-V600E mutations,which provides a basis for guiding the treatment of colorectal cancer and predicting the prognosis of patients.MethodThis study mainly iused ddPCR(Droplet digital PCR)technology to analyze the plasma samples collected from clinical patients,and explored the correlation between plasma cfDNA-related target levels and actual clinical conditions.At the same time,by detecting the mutation of BRAF-V600E in plasma ctDNA,and comparing the test results with gold standard clinical tissue biopsy,the relevant authenticity and predictive indexes of ctDNA for colorectal cancer BRAF-V600E mutation were calculated.ResultThis study analyzed plasma and clinical data from 74 patients.The BRAF V600E mutation was detected by digital PCR(ddPCR)and clinical pathology biopsy.Comparison of plasma ctDNA with tissue detection mutations showed that the BRAFV600E mutation coincidence rate was 56.76%,the sensitivity was 28.13%,and the specificity was 78.57%.At the same time,the plasma cfDNA levels of some patients were also tested,and the difference in cfDNA between 41 patients without metastasis and 14 patients with metastases was statistically significant(p = 0.0003).The cfDNA content of patients without metastasis was positively correlated with tumor size,R2 = 0.5683,p<0.0001.Conclusion:The digital PCR(ddPCR)detection of plasma ctDNA BRAF-V600E mutation in colorectal cancer patients is consistent with the results of immunohistochemical DNA BRAF-V600E mutation detection in clinical tissue biopsy.The specificity of ddPCR detection is good and has certain clinical reference value.The level of plasma cFDNA in patients with colorectal cancer can reflect the tumor volume and the risk of distant metastasis to some extent.