However, “Further investigation, including mechanistic studies, well-designed cohort studies, and possibly controlled trials, is needed,” the authors caution.
Dr. Zhi- Jiang Zhang, with the School of Public Health at Shanghai Jiao Tong University, China, and colleagues note that the risk of liver cancer is approximately doubled in patients with diabetes. Also, earlier studies have indicated that metformin may have a preventive effect against liver cancer as well as colorectal cancer and several other types of cancer.
To investigate further, the team searched the literature for case-control studies or cohort studies that examined the effect of metformin on hepatocellular carcinoma or primary liver cancer in patients with type 2 diabetes.
Data were abstracted from 5 relevant studies involving a total of 105,495 type 2 diabetics. Compared to no metformin treatment, metformin use was associated with an odds ratio of 0.38 for liver cancer (p
“A latency time period was considered in four of the five included studies, although the possibility of reverse causation is not completely ruled out,” Dr. and colleagues note.
They comment that metformin would be attractive for cancer chemoprevention if it is ultimately shown to reduce the risk of liver cancer, since it is well tolerated and inexpensive. “In this regard, it is instructive that the less developed countries have been disproportionately affected by liver cancer, accounting for nearly 85% of total new liver cancer cases worldwide. Thus, the affordability of metformin is important for accessibility to the general population.”