Metformin and the Incidence of Cancer in Patients With Diabetes: A Nested Case-Control Study

Diabetes is associated with an increased risk of various forms of cancer, such as cancer of the liver, colon, pancreas, breast, bladder, and kidney. Metformin, widely given to patients with type 2 diabetes, works by inhibiting hepatic glucose production through an LKB1 (serine-threonine liver kinase B1)/AMP-activated protein kinase (AMPK)–mediated mechanism. LKB1 is a well-recognized tumor suppressor. Activation of AMPK by LKB1 plays an important role in inhibiting cell growth. It has been suggested that metformin use in patients with diabetes may reduce their risk of cancer (1). Some studies have reported that diabetic patients taking metformin showed decreased cancer risk (2,3). However, several studies have shown that metformin does not reduce the risk of cancer in patients with diabetes (4,5). Little information is available on the subject considering non-Caucasian ethnicity. We used representative National Health Insurance datasets for Taiwan to form a cohort to …