The goal of this randomized crossover clinical trial is to evaluate the efficacy of Clostridium butyricum MIYAIRI 588 (CBM588) in reducing colorectal adenomatous polyp recurrence in adult patients with a history of colorectal polyps.

The main questions it aims to answer are:

• Does CBM588 reduce the recurrence of colorectal adenomatous polyps?
• Does CBM588 lead to a sustained decrease in polyp burden over time? Researchers will compare a group receiving CBM588 in the first year to a group receiving CBM588 in the second year (after a washout period) to determine whether CBM588 effectively lowers polyp recurrence rates and adenoma prevalence.

This randomized crossover clinical trial evaluates the effect of Clostridium butyricum MIYAIRI 588 (CBM588), a butyrate-producing probiotic, on colorectal adenomatous polyp recurrence. Participants who had undergone complete polypectomy were randomly assigned into two groups:

• Group A: Received CBM588 for one year, followed by a washout period and no treatment in the second year.
• Group B: Did not receive CBM588 in the first year but received it in the second year after a washout period.

Annual colonoscopy assessments were conducted to evaluate polyp count, type, and location. The primary outcome measure is adenoma recurrence. This study was conducted at a tertiary medical center and received Institutional Review Board (IRB) approval (KMUHIRB-F(I)-20170010). All participants provided informed consent.

Inclusion Criteria:

• Adults with a history of colorectal adenomas that had been completely removed by endoscopic resection within the past three years, and who presented with recurrent colorectal polyps detected during surveillance colonoscopy
• Willingness to undergo follow-up colonoscopies at study intervals
• No antibiotic or probiotic use for at least three months before study entry
• Written informed consent obtained

Exclusion Criteria:

• History of colorectal cancer or other gastrointestinal malignancies
• Diagnosis of inflammatory bowel disease or familial adenomatous polyposis
• Use of antibiotics and other probiotics during the study period

We do not plan to share individual participant data (IPD) from this study. The primary reasons include privacy concerns, ethical considerations, and regulatory restrictions. The data contain sensitive health information, and sharing could compromise participant confidentiality. Additionally, there are no institutional or legal frameworks in place to support external data sharing for this study.