Colorectal cancer is said to be the second most common cancer in Japan, and urgent measures are required.Although mortality is reduced by polypectomy, recurrence after resection and the onset of cancer remain issues. "Prevention" is the ultimate cancer control, but "chemical prevention" performed by administration of medicines includes aspirin, which is clinically applied to prevent myocardial infarction.However, for colorectal cancer, although some analgesics have a preventive effect, they have side effects, and a preventive method has not been established.

　Metformin is a widely prescribed diabetes treatment drug worldwide, but Professor Nakajima and his group have been paying attention to this drug for some time and reported that it suppresses colorectal tumors in the treated mice.Based on this finding, metformin or placebo (placebo) was randomly assigned to patients who had undergone colorectal polyps and did not relapse, and a comparative study was conducted. One year later, endoscopy revealed that the new incidence / recurrence rate of pre-colorectal cancer lesions was 1% in the metformin group and 32% in the placebo group, showing the usefulness of metformin as a chemopreventive agent for colorectal cancer. Showed sex.In addition, no serious side effects of metformin were observed during the study period.

　Metaformin is a drug that meets all of the conditions required for a chemopreventive drug: "less side effects," "clear mechanism of action," "easy to take," and "cheap."In addition, because it is an existing drug, it may lead to a reduction in new drug development costs.However, since it is necessary to follow up for a long period of time and further study whether it really suppresses the development of colorectal cancer, future results are expected to be reported.