Metagenomic analysis reveals effects of gut microbiome in response to neoadjuvant chemoradiotherapy in advanced rectal cancer

Neoadjuvant chemoradiotherapy can enhance survival rate of patients with advanced rectal cancer, but its effectiveness varies considerably. Previous studies have indicated that gut microbes may serve as biomarkers for predicting treatment efficacy. However, the specific roles of the gut microbiome in patients who have good response to nCRT remains unclear. In this study, shotgun metagenomic sequencing technology was used to analyze the fecal microbiome of patients with varying responses to nCRT. Our findings revealed that beneficial intestinal bacteria and genes from different metabolic pathways (carbohydrate metabolism, amino acid metabolism, and sulfur metabolism) were significantly enriched in patients with good response. Additionally, causal relationship in which microbial-derived GDP-D-rhamnose and butyrate could influence the response to nCRT was clarified. Our results offered new insights into the different response to nCRT, and provided valuable reference points for improving the effectiveness of nCRT in patients with advanced colorectal cancer. • The causal relationship between gut microbiome and response to nCRT were revealed. • Intestinal beneficial species significantly increased in patients with good response to nCRT. • Genes from carbohydrate metabolism and histidine biosynthesis significantly increased. • Potential microbial synthesis of butyrate and GDP-D-rhamnose influence response to nCRT.