Source: Schloss PD. Cancer Prev Res. 2014; doi:10.1158/1940-6207.CAPR-14-0129.
August 07, 2014
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Gut microbiome represents novel biomarker in colorectal cancer

Source: Schloss PD. Cancer Prev Res. 2014; doi:10.1158/1940-6207.CAPR-14-0129.
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Analysis of the gut microbiome significantly improved clinical ability to differentiate between patients with precancerous adenomatous polyps and those with invasive colorectal cancer compared with fecal occult blood testing.

“A person’s gut microbiome is the collection of all the bacteria in their gut,” Patrick D. Schloss, PhD, associate professor in the Department of Microbiology and Immunology at the University of Michigan, said in a press release. “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.”

Based on prior studies that suggested patients with colorectal cancer exhibited an abnormal gut microbiome structure vs. healthy patients, Schloss and colleagues examined stool samples from 90 individuals: 30 patients with precancerous adenomatous polyps, 30 patients with invasive colorectal cancer and 30 healthy control individuals.

The researchers extracted and analyzed microbial genomic DNA from the stool samples to identify gut microbiome signatures for each patient group. Schloss and colleagues assessed patients for known clinical risk factors for precancerous adenomatous polyps, including age, gender, race/ethnicity, BMI and current medications.

The researchers generated logit models using both clinical and microbiome data as independent variables to contrast dissimilarities across patient groups. As a basis for comparison, researchers also evaluated the likelihood of adenoma detection using guaiac fecal occult blood test in these three patient groups.

According to study results, gut microbiome data, when combined with known risk factors for colorectal cancer, demonstrated a 4.5-fold improved ability to predict precancerous adenomatous polyps. In addition, combining risk factor and gut microbiome data enabled 5.4-fold improved prediction of invasive colorectal cancer.

“We found that the composition of the gut microbiome allowed us to identify who in our study had precancerous adenomatous polyps and who had invasive colorectal cancer,” Schloss said. “If our results are confirmed in larger groups of people, adding gut microbiome analysis to other fecal tests may provide an improved, noninvasive way to screen for colorectal cancer.”

The researchers also determined that gut microbiome signatures were superior to fecal occult blood testing in differentiating patients with precancerous adenomatous polyps (area under the curve= 0.617) from those with invasive colorectal cancer (area under the curve=0.952).

“The feasibility, lack of invasive procedures, ability complement existing screening methods and the strength of signal seen in this study support the further investigation and application of microbial biomarkers from stool as a method for colorectal cancer screening,” Schloss and colleagues wrote.

Disclosure: The researchers report no relevant financial disclosures.