| Background According to cancer statistics in 2015,the mortality of colorectal cancer ranked fifth in China.Eearly diagnosis and treatment for colorectal cancer is of great significance.Early cancer screening had been proved effective in decreasing the incidence and mortality of colorectal cancer.Among the existing screening methods for colorectal neoplasms,colonoscopy can detect the whole colon and identify the location and nature of the lesions with high accuracy,but it is an invasive examination with the risk of bowel perforation and bleeding.Fecal occult blood test is convenient and non-invasive,besides,it is of high sensitivity and specificity.However,it still can not meet the needs of colorectal cancer screening.So we have to search for a non-invasive,convenient and accurate screening method for colorectal neoplasms screening.In recent years,many kinds of biomarkers in blood and stool had been studied and used to detect cancer,such as gene mutation,methylation and so on.In this study,stool DNA was extracted for detection of biomarkers and mutations,and hemoglobin in stool samples were detected by immunoassays.A non-invasive,convenient and accurate screening method was developed by valuating the performance of each biomarker and the combination of them.Methods Stool samples of patients in general surgery or digestive department of the First Affiliated Hospital of Soochow University from August 2017 to October 2018 were collected,including 102 colorectal cancer,20 colorectal adenoma,6 hyperplastic polyps patients and 105 normal controls.Detailed clinical information were recorded.All patients and normal controls were divided into two groups including high-risk group(colorectal cancer and colorectal adenoma patients,same as colorectal neoplasms)and low-risk group(hyperplastic polyp patients and colonoscopy-negative controls).Stool DNA was extracted for detection of methylation(BMP3,NDRG4,SDC2 and SFRP2)and KRAS mutations.Meanwhile,hemoglobin in stool samples were detected by immunoassays.logistic regression model was used for classification,and ROC curve was drew to evaluate the performance of each biomarker and the combinations of them.Meanwhile,the positive rate in colorectal cancer in serum biomarkers was calculated.Results1.The result of single stool-based biomarkerA logistic regression model was built with Ct values of single stool-based DNA biomarker.The accuracy of each stool biomarkers and their ranks were showed as:FIT(80.69%)>SDC2(77.68%)>SFRP2(75.11%)>KRAS(69.96%)>NDRG4(65.24%)>BMP3(59.66%).2.The result of multi-target stool-based biomarkersBy stepwise regression analysis,a combination composed of KRAS mutations,methylation of SDC2 and SFRP2,fecal occult blood testing and reference gene GAPDH was well-behaved in the screening of colorectal cancer and adenoma.This combination showed a sensitivity of 91.4%for colorectal cancer and 60%for adenoma at the specificity of 86.1%.3.Comparation between multi-target stool-based biomarkers and conventional serum biomarkers in colorectal cancer screeningThe positive rate of most of the conventional serum biomarkers was less than 20%in colorectal cancer patients,which was significantly lower than multi-target stool-based biomarkers with a sensitivity of 91.4%,suggesting its poor sensitivity in the screening of colorectal cancer.4.Elevated human DNA in stools of high-risk groupCt values of reference genes for KRAS mutation detection(ACTB)and DNA methylation detection(GAPDH)which reflected the quantity of human DNA in stool to some extent showed a significant difference between high-risk group and low-risk group(P<0.0001),indicating that the quantity of human DNA might also be applied for colorectal neoplasms screening.Conclusion The results showed that the multi-target stool-based biomarkers was a non-invasive and convenient method for colorectal cancer screening with high sensitivity and specificity,which had higher accuracy compared with conventional serum biomarkers and single stool-based biomarker as well. |
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