A prospective, single-centre, randomized, double-blind controlled study protocol to study whether long-term oral metronidazole can effectively reduce the incidence of postoperative liver metastasis in patients with colorectal cancer.

Introduction: Fifteen to 25% of patients with colorectal cancer have combined liver metastases at the time of diagnosis, whereas an additional 15 to 25% will develop liver metastases after curative resection of primary colorectal cancer, with the vast majority (80-90%) of liver metastases unresponsive to curative resection at first. Colorectal cancer liver metastasis is also the leading cause of death in patients with colorectal cancer. In recent years, several studies have demonstrated that intestinal flora, especially Fusobacterium nucleatum, plays a crucial role in the development of colorectal cancer liver metastasis, so we hypothesized that long-term metronidazole use could effectively reduce the incidence of postoperative liver metastasis in colorectal cancer patients.

Methods/design: This study is a prospective, single-centre, randomized, double-blind controlled study in which 300 patients will be randomly assigned to the test group or the control group in a 1:1 allocation ratio. The aim of this trial is to demonstrate that long-term oral antibiotics can effectively reduce the incidence of postoperative liver metastasis in patients with colorectal cancer.

Ethics And Dissemination: Ethics approval was obtained from the Ethics Committee at the Chinese Ethics Committee of Registering Clinical Trials (ChiECRCT20210229). The results of this study will be disseminated at several research conferences and as published articles in peer-reviewed journals.

Trial Registration: Chinese Clinical Trial Registry ChiCTR2100046201. Registered on July 05, 2021.