Abstract 2804: Comparative analysis of microbial diversity and abundance in colorectal cancer patients before and after surgery

Abstract Background: Previous studies have indicated differing patterns of the microbiome in colorectal cancer (CRC) patients compared to healthy individuals. Yet, the changes in microbial features of CRC patients before and after surgery remain underexplored. This study aims to investigate the impact of surgical intervention on the gut microbial diversity and abundance at the patient level. Methods: This hospital-based study analyzed data from 36 CRC patients who underwent CRC surgery at the Department of Surgery, Seoul National University Hospital between January 2020 and May 2022. Fecal samples from these patients were collected twice, both before surgery and during the post-surgery follow-up period. DNA extraction from stool specimens was performed using the MAG-Bind Universal Pathogen kit. This was followed by amplification and sequencing of the 16S rRNA gene V3-V4 region, with subsequent bioinformatics analyses conducted using QIIME 2. To compare the alpha diversity indices of patients before and after surgery, we employed both the paired t-test and the Wilcoxon signed-rank test. Results: Out of the 36 patients, 21 were male and 15 were female, with a mean age of 63. 8 years. The average duration between surgery and post-surgery fecal sample collection was 2. 3 years. Post-surgery, the alpha diversity indices decreased compared to pre-surgery, but the differences were not significant, except for Faith's PD. At the phylum level, Firmicutes and Actinobacteriota, both recognized as beneficial bacteria, increased in abundance after surgery, while Bacteriodota, typically considered harmful, significantly decreased. At the genus level, variations in microbial abundance also showed an increase in Blautia, Bifidobacterium, and Collinsella, and a decrease in Enterococcus, Romboutsia, and Faecalibacterium. The rise in Bifidobacterium abundance following surgery suggests a gut environment altered by the surgery to favor beneficial bacteria. However, a specific species decline in Bifidobacterium adolescentis was observed, highlighting that CRC surgery may have distinct impacts on different bacterial species. Conclusions: Our study indicates a slight decline in gut microbiome diversity following surgery. At the phylum level, there was an observed increase in beneficial bacteria and a decrease in harmful bacteria post-surgery, suggesting potential health improvements in CRC patients. Further research, particularly with a larger sample size and encompassing a broader range of bacteria, is needed to better understand the patterns and implications of microbiome variation in relation to surgical outcomes. Such insights could be pivotal in optimizing patient care and recovery strategies post-surgery. Citation Format: Hyeree Park, Min Jung Kim, Ji Won Park, Seung-Yong Jeong, Aesun Shin, Sung-Yup Cho, Eun Sung Jung, Dong Ho Suh, Sunyoung Lee, Yu Jin Park. Comparative analysis of microbial diversity and abundance in colorectal cancer patients before and after surgery abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2804.