Japanese Trial Shows Reduced Risk of Subsequent Colorectal Adenomas and Polyps With Low-Dose Metformin
Treatment with low-dose metformin reduced the risk of metachronous colorectal adenomas and polyps over 12 months in nondiabetic patients who had undergone endoscopic polypectomy, according to a report by Higurashi et al in The Lancet Oncology.
Study Details
In the double-blind phase III trial, 151 patients from 5 sites in Japan were randomized to receive metformin at 250 mg/d (n = 79) or placebo (n = 72), with randomization stratified for institute, age, sex, and body mass index. Of them, follow-up endoscopy at 1 year was performed in 71 metformin patients and 62 placebo patients.
Reduced Recurrence
Hyperplastic polyps or adenomas (total polyps) were found in 38.0% (95% confidence interval [CI] = 26.7%–49.3%) of the metformin group vs 56.5% (95% CI = 44.1%–68.8%) of the placebo group (risk ratio [RR] = 0.67, P = .034). Adenomas were found in 30.6% (95% CI = 19.9%–41.2%) vs 51.6% (95% CI = 39.2%–64.1%; RR = 0.60, P = .016).
Overall, there were 44 polyps (37 adenomas and 7 hyperplastic polyps) in the metformin group vs 66 polyps (59 adenomas and 7 hyperplastic polyps) in the placebo group (median = 0 vs 1 for polyps, P = .041; 0 vs 0 for adenomas, P = .037).
Adverse Events
Adverse events occurred in 11% of patients, and all were grade 1. Adverse events consisted of diarrhea, rash, and constipation in the metformin group and abdominal pain, diarrhea, constipation, and alopecia in the placebo group. No serious adverse events were observed.
The investigators concluded: “The administration of low-dose metformin for 1 year to patients without diabetes was safe. Low-dose metformin reduced the prevalence and number of metachronous adenomas or polyps after polypectomy. Metformin has a potential role in the chemoprevention of colorectal cancer. However, further large, long-term trials are needed to provide definitive conclusions.”
The study was funded by the Ministry of Health, Labour, and Welfare of Japan.
Atsushi Nakajima, MD, of Yokohama City University School of Medicine, is the corresponding author of The Lancet Oncology article.
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