P0262 - Fecal Microbiome Associated With Both Colon Adenomas and Lifetime Colorectal Cancer Risk

Sarah A. Alharfi, MD¹, Gregory Cooper, MD², Mahmoud Ghannoum, PhD³, Nancy Furey, RN¹, Hilmi Al-shakhshir, ^3
1University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, OH; ²University Hospitals Case Medical Center, Cleveland, OH; ³Case Western Reserve University, Cleveland, OH

Introduction: Increasing data indicates the gut flora including bacteria and fungi (mycobiome) combined with environmental factors are important in the pathogenesis of colorectal cancer (CRC). Whereas numerous studies have examined the bacteriome in CRC, very few have examined the mycobiome. Understanding differences in the microbiome in patients with colon neoplasia will foster the development of biomarkers that may enable early detection of CRC and advanced adenoma to improve screening strategies.

Methods: We conducted a prospective cohort of subjects 50-75 yrs, referred for colonoscopy. Patients with high-risk genetic conditions, inflammatory bowel disease, GI bleeding in the past month, or colonoscopy within the past 5 yrs were excluded. Prior to the colonoscopy preparation, the National Cancer Institute (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 & fungal species. In addition, we compared the microbiome according to predicted lifetime risk probability of CRC, which was derived from the NCI tool.

Results: Among 34 individuals, we identified 10 (29.4%) patients with one or more adenomas, including 2 with advanced adenomas & 2 with sessile serrated adenomas. Only 2 patients were FIT positive, one of whom had an advanced adenoma. The median predicted lifetime CRC risk was 2.75%. The prevalence of adenoma in the 1^strisk quartile was 1.5% compared to 62.5% in the 4^thquartile (p< 0.001). The measured alpha diversity was somewhat higher in patients with adenoma (p=0.1). Nine unique species were found in the adenoma group. We identified 2 bacterial species, B.obeum & L.boronitolerans, which showed an increased relative abundance among patients with adenoma [mean=0.0002 & 0.0007, p=0.01 & 0.03, respectively]. The lifetime CRC risk was associated with 2 specific bacterial species, P.distasonis [p= 0.05] & E.hermannii [p= 0.09], whereas a negative correlation was found in 4 other species [P< 0.1]. No associations were seen with fungal species & adenoma prevalence or lifetime CRC risk.

Discussion: In addition to a strong correlation of predicted CRC risk and adenoma prevalence, we also found important differences in specific bacterial but not fungal species and both adenoma prevalence and CRC risk. Given these associations, larger trials are needed to potentially implement further data in the clinical setting.


Figure: Predicted Lifetime Risk correlated with Species abundances


Disclosures:
Sarah Alharfi indicated no relevant financial relationships.
Gregory Cooper indicated no relevant financial relationships.
Mahmoud Ghannoum indicated no relevant financial relationships.
Nancy Furey indicated no relevant financial relationships.
Hilmi Al-shakhshir indicated no relevant financial relationships.


Sarah A. Alharfi, MD¹, Gregory Cooper, MD², Mahmoud Ghannoum, PhD³, Nancy Furey, RN¹, Hilmi Al-shakhshir, ³. P0262 - Fecal Microbiome Associated With Both Colon Adenomas and Lifetime Colorectal Cancer Risk, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.