Abstract 123P
Background
Recent research has examined the connection between gut microbiome and colorectal cancer (CRC) development and treatment response, revealing distinct microbiome patterns across healthy individuals, adenoma patients, and CRC patients. Dysbiosis is linked to lifestyle factors like diet and diseases like CRC. Chemotherapy can further alter microbiome, potentially leading to inflammation. Research indicates that a rich microbiome enhances treatment response in mice. This study compares the microbiomes of CRC patients with non-cancer (NC) subjects to identify potential CRC microbiome markers. It also assesses CRC patients' microbiome before and after treatment to understand therapy effects.
Methods
32 NC controls and 17 newly diagnosed stage IV CRC patients were enrolled, none had a history of autoimmune or inflammatory bowel diseases. CRC patients submitted stool samples before treatment (B) and 3-6 months after (A). All patients took chemotherapy, except one took immunotherapy. Stool samples were collected, resuspended in Qiagen RNAlater, and sent for metagenomics analysis.
Results
Microbiome composition was analyzed across 3 groups: 32 NC, 17 B, and 10 A. 2 phyla, Bacteroidetes and Firmicutes, were predominant in all samples. In microbiome research, the Firmicutes/Bacteroidetes ratio (RF/B) is utilized as an indicator of dysbiosis. The average RF/B in NC was < 1, it decreased in B and further diminished in A. To validate the findings, we compared proportions of samples in each group with RF/B < 1. We observed a significant increasing trend (p<0.05) of this proportion across NC versus B versus A. Beta diversity showed that NC clustered away from A, with B in between. This was further validated using alpha diversity within each sample which significantly decreased between NC and A (FDR = 0.002) and between B and A (FDR = 0.04). Table: 123P
| RF/B | NC | B | A | Total |
| < 1 | 11 (34%) | 9 (53%) | 6 (60%) | 26 |
| > 1 | 21 (66%) | 8 (47%) | 4 (40%) | 32 |
| Total | 32 | 17 | 10 | 59 |
Conclusions
The gut microbiome's importance in CRC outcomes is widely acknowledged. This study shows that dysbiosis is evident in CRC patients, particularly after treatment.
Legal entity responsible for the study
The authors.
Funding
Northwestern Kiphart Grant.
Disclosure
All authors have declared no conflicts of interest.