Synbiotics protected radiation-induced tissue damage in rectal cancer patients: A controlled trial

Colorectal cancer (CRC), particularly rectal cancer, often requires neoadjuvant radiotherapy (RT) as part of its treatment plan. Although effective, RT can cause significant gastrointestinal side effects. Because the onset of RT-induced tissue injury can be anticipated, there is an opportunity to apply preventive measures before the damage occurs. This study aimed to assess whether prebiotic and synbiotic interventions could mitigate RT-induced gut injury by modulating the mucosa-associated microbiota, reducing inflammation, and enhancing gut barrier function in patients undergoing RT for rectal cancer.

Thirty patients with rectal adenocarcinoma scheduled for preoperative short-term RT (5 × 5 Gy) were divided into three groups: a control group (Ctrl), a prebiotic group (Fiber) receiving oat bran, and a synbiotic group (Synbiotics) receiving oat bran with L. plantarum HEAL19 and blueberry husks. The study products were administered daily for two weeks, starting one week before RT. Blood, faecal, and biopsy samples were collected before and after RT to evaluate inflammatory markers, intestinal permeability, histopathological changes, and mucosa-associated microbiota.

The Fiber and Synbiotics groups exhibited a significant reduction in white blood cell counts following RT (p = 0.01 for both), whereas the Ctrl group did not demonstrate a significant change. However, there was no significant difference in the magnitude of change in white blood cell counts among the three groups (p = 0.12). Histopathological analysis revealed that the Synbiotics group had reduced inflammation and fibrosis compared to the Fiber and Ctrl groups. Although RT reduced bacterial diversity overall, the Synbiotics group preserved a greater proportion of bacterial species, experiencing only a 25.1 % reduction compared to a 55.4 % reduction in the Fiber group.

Synbiotic interventions may protect rectal mucosa by reducing inflammation and modulating mucosa-associated microbiota. The effects were primarily localized to the tissue, reflecting the short-term duration of treatment. While immediate benefits were observed, longer-term interventions should be explored to reduce systemic inflammation.