Abstract
Objectives Colorectal cancer (CRC) is the second leading cause of cancer-related deaths. The development of preventive strategies in CRC has been the subject of much research. Multiple studies have shown an association between diabetes and CRC. In addition to its glucose-lowering properties, metformin might have an additional role in the prevention and treatment of CRC.
Our objective was to summarize findings on role of metformin in colorectal cancer.
Methods We conducted a systematic review of the PubMed and Cochrane databases from January 2005 to December 2017 in search for studies on the association between metformin and CRC.
Results Of the total of 189 studies identified by the search, we excluded 123 studies and reviewed the remaining 66 studies on cell lines, animals, patients with diabetes, and healthy subjects. In vitro and animal studies have shown a protective effect of metformin use on the incidence of CRC and amplification of the therapeutic effects of CRC chemotherapy. Studies on patients with type 2 diabetes treated with metformin analyzed data on total of 146 496 patients. The results of those studies on the role of metformin in CRC suggest risk reduction and potential applications within therapeutic regimens, although some of those are conflicting.
Conclusion Further studies are warranted to define the role of metformin in both prevention and treatment of CRC.
Key words
colorectal cancer - diabetes mellitus - metformin - cancer risk - cancer prevention
