Researchers at the University of Michigan have discovered a positive correlation between the presence of certain gut bacteria in the digestive system to increased risk of developing colorectal cancer. The study was published in Cancer Prevention Research, a journal by the American Association for Cancer Research. The current standards of colorectal cancer are either faecal occult blood testing (FOBT) or the rather invasive but effective colonoscopy.

The study was conducted using the stool samples of 90 individuals. 30 individuals were healthy, 30 had precancerous polyps and 30 had colorectal cancer. All the stool samples were sequenced to map the gut microbiome of each individual.

“A person’s gut microbiome is the collection of all the bacteria in their gut,” said lead investigator and associate professor in the Department of Microbiology and Immunology at the University of Michigan Ann Arbor, Dr. Patrick D. Schloss. “The number of bacteria in the gut is huge; it outnumbers the number of cells in our bodies 10 to one, and the diversity of the bacteria present is critical to our health. By sequencing the V4 region of the 16S rRNA gene we were able to identify the bacteria present in each individual’s gut microbiome.”

Results from the study showed that each group had a unique gut bacterial microbiome signature, thus successfully allowing for the screening of their respective conditions without doing further, more invasive tests. The study further accounted for age and race factors, and found an increased accuracy of prediction for precancerous polyps by 4.5 times when compared to the use of the gut microbiome signature alone. The accuracy was further raised to 5.4 times when body mass index (BMI), an additional risk factor for colorectal cancer, was accounted for.

While the study shows great promise for a highly accurate, non-invasive screening method for colorectal cancer risk, the population size of the study conducted is still not enough warrant the full clinical use of the screening. The next step is to conduct the same studies on a larger population and yield identical results. The study further notes that the gut microbiome test shows greater promise when paired with an FOBT.

“Our data show that gut microbiome analysis has the potential to be a new tool to noninvasively screen for colorectal cancer,” said Schloss. “We don’t think that this would ever replace other colorectal cancer screening approaches, rather we see it as complementary.”