Prospective, longitudinal analysis of the gut microbiome in patients with locally advanced rectal cancer predicts response to neoadjuvant concurrent chemoradiotherapy

Abstract Background Neoadjuvant concurrent chemoradiotherapy (nCCRT) is a standard treatment for locally advanced rectal cancer (LARC). The gut microbiome may be reshaped by radiotherapy through its effects on microbial composition, mucosal immunity, and the systemic immune system. We sought to clarify dynamic, longitudinal changes in the gut microbiome and blood immunomodulators throughout nCCRT and to explore the relationship of such changes with outcomes after nCCRT Methods A total of 39 LARC patients were recruited in this study. Fecal samples and peripheral blood samples were collected from 39 LARC patients before, during nCCRT (at week 3), and after nCCRT (at week 5). The gut microbiota and the community structure were analyzed based on the 16S rRNA sequencing of the V3-V4 region. Levels of blood immunomodulatory proteins were measured with a Millipore HCKPMAG-11K kit and Luminex 200 platform (Luminex, USA). Results Cross-sectional and longitudinal analysis revealed that the gut microbiome profile and enterotype exhibited characteristic variations in patients with good response (TRG 0–1) vs poor response (TRG 2–3) to nCCRT. Sparse partial least squares regression and canonical correspondence analyses showed multivariate associations between specific microbial taxa, host immunomodulatory proteins, immune cells, and outcomes after nCCRT. An integrated model consisting of baseline Clostridium sensu stricto 1 levels, fold changes in Intestinimonas, blood levels of the herpes virus entry mediator (HVEM/CD270), and lymphocyte counts could predict good vs poor outcome after nCCRT (area under the receiver-operating characteristics curve [1] = 0.821; area under the precision-recall curve [AUPR] = 0.911). Conclusions Our results showed that longitudinal variations in specific gut taxa, associated host immune cells and immunomodulatory proteins before and during nCCRT could be useful for early predictions of the efficacy of nCCRT, which could guide the choice of individualized treatment for patients with LARC.