Microbiome Dynamics During Rectal Cancer Surgery: Insights from NIHR IntAct Trial

Overview

This study characterized perioperative changes in the rectal microbiome of 202 patients undergoing rectal cancer surgery. Significant shifts in microbial diversity and composition were observed, influenced by factors such as smoking, hospital site, bowel preparation, and use of defunctioning stoma. Although subtle microbiome differences were noted between patients with and without anastomotic leak, no definitive association was established.

Background

The gut microbiome plays a crucial role in health and disease, with emerging evidence linking it to postoperative outcomes after rectal cancer surgery. Anastomotic leak, a serious complication, may be influenced by microbial populations producing collagen-degrading enzymes. Preclinical studies suggest microbiome dysbiosis impairs anastomotic healing, but human data remain limited. The NIHR IntAct trial microbiome substudy aimed to elucidate perioperative microbiome changes and their relationship to clinical outcomes.

Data Highlights

Key Findings

• Alpha-diversity of the rectal microbiome decreased over the perioperative period.
• Postoperative increases were observed in Enterococcus and Prevotella genera.
• Defunctioning stoma use was associated with lower alpha-diversity and increased abundance of Pseudomonas and Streptococcus.
• Collagenase-producing bacteria were detected in 43.6% of postoperative samples, indicating potential tissue-degrading activity.
• No significant differences in overall alpha- or beta-diversity were found between patients with and without anastomotic leak, though subtle differences in low-abundance taxa existed.
• Factors such as smoking, hospital site, bowel preparation, and antibiotic use significantly influenced microbiome composition at various time points.

Clinical Implications

Understanding perioperative microbiome shifts can inform strategies to optimize surgical outcomes in rectal cancer patients. Although no clear microbiome signature predicted anastomotic leak, the presence of collagenase-producing bacteria highlights a potential target for intervention. Tailoring perioperative care, including antibiotic regimens and stoma use, may modulate microbiome composition and reduce postoperative complications.

Conclusion

This largest-to-date study reveals significant perioperative alterations in the rectal microbiome influenced by clinical and treatment factors. While subtle microbiome differences were noted in patients with anastomotic leak, further research is required to clarify their clinical relevance and potential for guiding preventive strategies.

References

1. NIHR IntAct Trial Investigators 2024 -- Exploring Microbiome Alterations During Rectal Cancer Surgery