Abstract
Some patients may develop adverse events during neoadjuvant chemoradiotherapy combined with immunotherapy, influencing response rates. The roles of intestinal microbiome and its metabolites in therapeutic adverse events remain unclear. We collected baseline fecal samples from 21 patients with adverse events (AE group) and 11 patients without adverse events (Non-AE group). Their microbiota and metabolome were characterized using metagenomic shotgun sequencing and untargeted metabolomics. At the species level, the gut microbiota in the Non-AE group exhibits significantly higher abundance of Clostridium sp. Alistipes sp. and lower abundance of Lachnoclostridium sp. Weissella cibaria, Weissella confusa, compared to the AE group (p < .05). A total of 58 discriminative metabolites were identified between groups. Beta-alanine metabolism was scattered. Boc-beta-cyano-L-alanine and CoQ9 were significantly increased in patients without adverse events, while linoleic acid increased in patients with adverse events. The increased Alistipes sp. in the Non-AE group was positively correlated with Boc-beta-cyano-L-alanine and negatively correlated with linoleic acid (p < .05). We constructed a combined microbiome-metabolite model to distinguish Non-AE and AE patients with an AUC of 0.963 via the random forest algorithm. Our findings provided a novel insight into the interplay of multispecies microbial cluster and metabolites of rectal patients with adverse events in neoadjuvant chemoradiotherapy combined with immunotherapy. These microbiota and metabolites deserve further investigations to reveal their roles in adverse events, providing clues for better treatment scenarios.Trial registration number: ClinicalTrials.gov identifier: NCT05368051.