Moderate alteration to gut microbiota brought by colorectal adenoma resection.

BACKGROUND AND AIM: Microbial dysbiosis is involved in the development of colorectal cancer and its most common precancerous lesion, colorectal adenoma. Endoscopic resection is one of the procedures for primary prevention of colorectal cancer, yet little is known about how the endoscopic therapy influences gut microbiota. METHODS: We conducted a prospective study of 20 patients who underwent endoscopic resection of colorectal adenoma and analyzed the fecal microbiota before and 3 months after adenoma resection. MiSeq sequencing of 16S rRNA genes was performed to determine the alterations in microbial diversity and structure. To discriminate the microbiota of the two groups, random forest and receiver operating characteristic analysis were applied, and a genus-based microbiota signature was obtained. RESULTS: Despite few alterations in overall microbial structure after adenoma resection, the abundance of Parabacteroides revealed a significant increase postoperatively (3.8% vs 1.5%, 0.1160), and the microbiota signature of Parabacteroides, Streptococcus, and Ruminococcus showed an optimal discriminating performance of postoperative status with the area under the curve 0.788, P < 0.001. CONCLUSION: Fecal microbial alterations indicate the moderate influence of adenoma resection on gut microbiota and lay the groundwork for microbial prediction of adenoma recurrence. Larger sample studies are further required to validate the findings.

Fecal Clostridium symbiosum for Noninvasive Detection of Early and Advanced Colorectal Cancer: Test and Validation Studies.

OBJECTIVE: Current non-invasive early detection of colorectal cancer (CRC) requires improvement. We aimed to identified a fecal Clostridium symbiosum-based biomarker for early and advanced colorectal cancer detection. DESIGN: In the test stage, the relative abundance of Clostridium symbiosum (C. symbiosum) was measured by qPCR in 781 cases including 242 controls, 212 colorectal adenoma (CRA) patients, 109 early CRC (tumor restricted to the submucosa) patients, 218 advanced CRC patients. The prediction accuracy was compared to Fusobacterium nucleatum (F. nucleatum), fecal immunochemical test (FIT) and CEA (carcinoembryonic antigen) and validated in an independent cohort of 256 subjects. Current status of the trial:ongoing/still enrolling. Primary endpoint:June, 2017 (Clinicaltrials.gov Identifier NCT02845973). RESULTS: Significant stepwise increase of C. symbiosum abundance was found in CRA, early CRC and advanced CRC (P<0.01). C. symbiosum outperformed all the other markers in early CRC prediction performance. The combination of C. symbiosum and FIT achieved better performance (0.803 for test cohort and 0.707 for validation cohort). For overall discrimination of CRCs, the combination of all above markers achieved the performance of 0.876. CONCLUSIONS: Fecal C. symbiosum is a promising biomarker for early and noninvasive detection of colorectal cancer, being more effective than F. nucleatum, FIT and CEA. Combining C. symbiosum and FIT or CEA may improve the diagnosis power.