Researchers discovered that patients with cystic fibrosis (CF) have fewer short-chain fatty acid (SCFA)-producing bacteria and a greater population of bacteria associated with colorectal cancer compared to the general population. Their study is published in Colorectal Disease. 

Epidemiological studies demonstrate that individuals with CF have a higher risk of developing colorectal cancer compared to the general population. Estimates indicate that around 50% of the patients will have adenomatous polyps and 3% will have colorectal cancer by age 40. Scientists propose that this is due to dysfunctional CF transmembrane conductance regulator (CFTR) protein causing variations in the gut microbiota. 

Gilbert and colleagues conducted a systematic review to assess existing evidence regarding the microbiome of adult patients with CF and whether it corresponds with known colorectal cancer microbiome alterations. They conducted a literature search in 4 academic databases and excluded studies that were conducted on pediatric patients, lacked control groups, or did not use next-generation sequencing. 

Five studies were included in their final analysis. These studies were published between 2007 and 2021 and included between 12 and 112 participants. Importantly, all 5 studies required individuals in the control group to not be on antibiotic medication between 28 days to 1 year prior to specimen collection, improving the quality of the data collected. 

Read more about cystic fibrosis etiology 

The research team discovered that patients with CF significantly lacked gut microbial diversity and generally had reduced populations of Bacteroidetes, Proteobacteria, and Cyanobacteria. However, they generally had an increase in Fusobacterium, B. fragilis, and E. faecalis, which are linked with colorectal cancer.

In addition, they found that SCFA-producing bacteria were likely to be reduced in patients with CF. This creates an environment that makes tumorigenesis more likely. 

“Consistent across all studies, CF patients have lower levels of SCFA-producing bacteria and increased [colorectal cancer]-associated microbes,” the authors of the study concluded. “Given the high rates of adenomas and [colorectal cancer] in CF, this warrants further longitudinal investigation.” 


Gilbert B, Kaiko G, Smith S, Wark P. A systematic review of the colorectal microbiome in adult cystic fibrosis patientsColorectal Dis. Published online January 4, 2023. doi:10.1111/codi.16472