Fecal Microbiome Associated with Both Colon Adenomas and Lifetime Colorectal Cancer Risk.

BACKGROUND

Increasing data indicates the gut flora including bacteria and fungi combined with environmental factors are important in the pathogenesis of colorectal cancer (CRC). Understanding differences in the microbiome in patients with colon neoplasia will foster the development of biomarkers for early detection.

AIMS

Determine the association of microbiome with presence of adenomas and predicted CRC risk.

METHODS

In subjects referred for colonoscopy, the NCI CRC risk assessment tool was completed and stool for microbiome analysis as well as fecal immunochemical test (FIT) were collected. We calculated the microbiome alpha diversity using the Shannon index as well as individual bacterial and fungal species.

RESULTS

Among 34 patients, we identified 10 with one or more adenomas. Only 2 patients were FIT positive. The median predicted lifetime CRC risk was 2.75% and the prevalence of adenoma was higher in the fourth quartile (P < 0.001). The measured alpha diversity was somewhat higher in patients with adenomas (P = 0.07). We identified 4 bacterial species with an increased relative abundance among patients with adenomas [P < 0.5]. Lifetime CRC risk was associated with 2 specific bacterial species, P. distasonis & E. hermannii [P = 0.05 & 0.09, respectively]. No associations were seen with fungal species and adenoma prevalence or lifetime CRC risk.

CONCLUSIONS

In addition to a strong correlation of predicted CRC risk and adenoma prevalence, we also found important differences in specific bacterial species and both adenoma prevalence and CRC risk. Larger trials are needed to potentially implement further data in the clinical setting.