Prevention of Radiotherapy-Induced Enteropathy by Probiotics (PREP): Double-Blind Randomized Placebo-Controlled Trial

Probiotics are thought to be effective in the treatment of radiation-induced enteropathy (RIE). However, little is known regarding their efficacy in preventing RIE. In this prospective, randomized, double-blinded, placebo-controlled, single-center study, the incidence of grade 2 acute RIE was compared and the safety of probiotics was evaluated. Patients receiving pelvic radiotherapy for a minimum of 40 Gy at the pelvic level were randomized into two groups: (i) a probiotic group receiving Bacillus licheniformis from two weeks before radiotherapy until the end and (ii) a control group receiving a placebo with the same schedule. The toxicities of 234 patients were graded according to the Common Terminology Criteria for Adverse Events v5.0. Grade 1 RIE was observed in 65 (56%) of the probiotics group compared with 75 (64%) of the placebo group. Grade 2 RIE occurred in 30 patients (26%) in the probiotics group compared with 26 (22%) in the placebo group, indicating that probiotics failed in their preventive role compared with placebo (p = 0.493). Medication adherence rates were good, and no difference was observed between the two arms. These findings suggest that B. licheniformis does not significantly prevent RIE.