The human gut microbiome as a screening tool for colorectal cancerOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This study tested whether the gut microbiome could serve as a non-invasive screening tool for colorectal cancer. Researchers sequenced the V4 region of the 16S ribosomal RNA gene from stool. They compared microbiome profiles across the stages of tumor development and combined microbial data with clinical risk factors and a stool blood test. Using logistic regression and Bayesian methods, they asked whether microbes improve on existing screening beyond age, race, and body mass index.
Who was studied?
The sample was 90 adults providing whole stool, evenly split into healthy colons (n equals 30), colonic adenomas (n equals 30), and colonic carcinomas (n equals 30), all confirmed by colonoscopy and biopsy. Participants were recruited across four sites in Canada and the United States. Men, white participants, and those with higher body mass index were more likely to have cancer. This was a human cross-sectional study spanning precancer and cancer stages.
What were the most important findings?
Adding microbiome data markedly improved discrimination. For healthy versus adenoma, adding 5 taxa raised the model area under the curve to 0.896; for healthy versus carcinoma, adding 6 taxa reached 0.922. Carcinomas showed enrichment of oral-associated and Enterobacteriaceae taxa and loss of short-chain-fatty-acid producers like Lachnospiraceae. A microbiome screening test had a positive likelihood ratio of 71 versus 41 for the stool blood test. For a 65-year-old, microbiome data lifted adenoma probability from 0.17 percent to 10.67 percent, a more than 50-fold rise.
What are the greatest implications of this study?
The results show gut microbiome data can meaningfully sharpen non-invasive colorectal cancer screening, outperforming the stool blood test on sensitivity and complementing clinical risk factors. The distinct microbial shifts across stages also support colorectal cancer being a polymicrobial process, involving both gain of pathogens and loss of protective microbes. The study is small and cannot prove microbes cause tumors, so larger, more diverse validation cohorts are needed before clinical use.