Metformin for recurrent colorectal polyp or adenoma prevention after polypectomy in patients without diabetes mellitus: a prospective study

To reduce the burden of colorectal cancer (CRC), the chemopreventive effects of 1-year metformin on polyps or adenoma recurrence in patients without diabetes mellitus (DM) who underwent polypectomy were evaluated. Patients without DM aged between 40 and 70 years old, with no polyp or adenoma after polypectomy, were randomly assigned to the control (no intervention), low-dose (500 mg/day), or high-dose (1,000 mg/day) metformin groups in a 1:1:1 ratio. After the 1-year intervention, the numbers of polyps and adenomas were measured and recorded, then resected. Plasma lipid and blood glucose were measured at baseline and 1-year follow-up. Data from the three groups were compared statistically. A total of 272 patients were enrolled in the analysis. In the control group, 48.9% of patients had adenoma recurrence, which was significantly higher than those in the low-dose (30.8%, p=0.012) and the high-dose (29.9%, p=0.009) metformin group. For the number of recurrent adenomas per subject, the difference between the control and the high-dose metformin groups was significant (0.86±1.09 vs. 0.47±0.83, p=0.020). No significant difference among the three groups and between baseline and 1-year follow-up was found in the lipid and glucose parameters. In conclusion, 1-year metformin use reduced the prevalence of recurrent adenoma significantly in patients without DM after polypectomy and may not be related to lipid and glucose metabolism.