Objective  To investigate how gut microbiota changes during prostate cancer radiotherapy and decipher the relationship of gut microbiota with disease progression and chronic radiation enteritis.

Methods Thirty-one patients with prostate cancer were included in this study, admitted to The First Affiliated Hospital of Xinjiang Medical University from September 2022 to December 2023. The clinical data and stool samples of the patients were collected, and patients were followed up. The collected stool specimens were subjected to 16S rRNA sequencing to detect gut microbiota and bioinformatics analysis.

Results The relative abundance of phyla such as Firmicutes and Actinobacteria increased, and that of Bacteroidetes decreased (P<0.05) with an increasing radiotherapeutic dose, while beta diversity was significantly higher (P = 0.001). The relative abundance of the phylum Actinobacteria was significantly higher in the prostate cancer progression group than in the non-progression group (P<0.05), the relative abundances of genera such as Sutterella and Haemophilus were significantly higher in the progression group (P<0.05). That of Verrucomicrobia and its offshoots in Akkermansia was higher in the chronic radiation enteritis than in the non-enteritis group (P<0.05), while the relative abundances of Coprococcus_1 and Catabacter in the non-enteritis group were higher than those in the enteritis group (P<0.05).

Conclusions Radiotherapy dose accumulation significantly remodeled the floral structure. Sutterella and Haemophilus of the phylum Proteobacteria might be key flora in prostate cancer recurring early after treatment. An augmented abundance of Akkermansia might increase the risk of chronic radiation enteritis, whereas the flora under the Lachnospiraceae branch might exert aprotective effect against chronic radiation enteritis.