An Evaluation of the Fecal Microbiome in Lynch Syndrome.

Purpose: There is limited data regarding the fecal microbiome findings in patients with Lynch syndrome. We aimed to study the fecal micobiome of patients with Lynch syndrome with and without cancer.

Methods: We performed an observational study comparing the fecal microbiome of patients with Lynch syndrome (LS) with cancer with those without cancer. We included subjects older than 18 years with LS and excluded those with a history of colectomy or inflammatory bowel disease. We analyzed their fecal microbiome by 16S ribosomal subunit PCR amplification and performed comparative analyses.

Results: Eight patients were included: 3 of these with LS and cancer (LS-C) and 5 patients with LS and no cancer (LS-NC). We found non-significant differences at the phyla and genera level between the LS-C and LS-NC groups. At the phyla level, LS-C patients had a higher percentage of Bacteroidetes (42.2% vs. 28.5%; P = 0.068) and Verrucomicrobia (0.644% vs 0.0007%; P = 0.10), and a lower percentage of Firmicutes (48.3% vs. 65.4%; P = 0.078). At the genus level, LS-C patients had a higher rate of Akkermania (0.766% vs. 0.001%; P = 0.11). LS-C patients with endometrial cancer had a higher rate of Bacteroides (37.4% vs 17.3%; P = 0.10). LS-C patients had a lower rate of Pseudobutyrvibrio (0.74% vs. 2.71%; P = 0.10).

Conclusions: The fecal microbiome of LS patients with extraintestinal cancer differs that of LS patients without cancer. Further studies are needed to explore microbiome changes in these high risk patients.