LAUSR

Background: Previous studies have suggested the disturbance in the microbial composition followed by dysbiosis contribute to the onset of gastrointestinal malignancies, including colorectal cancer (CRC). However, the impact of microbiome on short-term postoperative complications after CRC surgery is not well investigated. This study aimed to investigate whether the gut microbial diversity and composition in CRC patients were associated with the occurrence of short-term postoperative complications. Methods: We linked the clinical data and preoperative sequencing data of fecal samples of 331 patients who underwent CRC surgery from 2017 to 2019 in Seoul National University Hospital. Short-term postoperative complications were defined as first complications that developed within 30 days of surgery. We used linear discriminant analysis (LDA) of effect size (LEfSe) in the Galaxy webserver to identify enriched bacteria in patients with and without complications. Then, we calculated microbial dysbiosis index (MDI) by each patient and compared them according to the complication status. Wilcoxon rank sum test was conducted to compare the alpha diversity indices according to the complication event. Subgroup analyses according to types of complications were also performed: surgical procedure-related (SP) group and nonsurgical procedure-related (NSP) group. Results: Overall, 84 patients (25%) developed short-term postoperative complications: SP group (n=39) and NSP group (n=45). From the LEfSe analysis, Bacteroides uniformis (LDA score: 3.64, p-value 0.04) and Clostridium colicanis (LDA score: 3.39, p-value 0.01) were enriched in patients who developed short-term complications, whereas Roseburia faecis (LDA score: 3.26, p-value 0.05), Bifidobacterium bifidum (LDA score: 2.98, p-value 0.03), Faecalibacterium sp. (LDA score: 3.12, p-value 0.02) and Prevotella nigrescens (LDA score: 2.87, p-value 0.05) were enriched in patients without complications. When compared with patients without complications, taxa related to class Gammaproteobacteria, genus Clostridium, species Roseburia faecis, and Desulfovibrio D168 were abundant in the SP group. Alpha diversity indices were not significantly different according to the complication status or the type of complication. MDI from the enriched bacteria were significantly higher in patients with complications compared to those without complications (p-value<0.001), and MDI of the SP group were also significantly higher than that of patients free of complications (p-value 0.001). Conclusion: Our study suggests a potential relationship between microbial composition and surgical outcome in CRC patients. No significant difference in alpha diversity was observed according to the occurrence or the type of complication. Further studies are needed to investigate the postoperative changes of microbial features. Citation Format: Hyeree Park, Tung Hoang, Min Jung Kim, Ji Won Park, Seung-Yong Jeong, Aesun Shin. Microbial diversity and composition according to short-term postoperative complication status in colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5892.