A Prospective Study Of The Influence Of Metformin On Cancer Risk And Prognosis In Diabetes

ObjectiveMetformin, a widely prescribed oral medication used as front-line therapy for type2diabetes, was recently found to have anticancer effects. These observations are supported by in vitro and in vivo evidence that metformin inhibits the growth of cancer cells. The objective of this study was to test the hypothesis that metformin use is associated with a reduced risk of cancer in people with type2diabetes and improve cancer prognosis.MethodsTo evaluate the relationship involving metformin and cancer, in an observational cohort study we identified people with type2diabetes in Liaocheng Pepole’s Hospital databases from January1,2000to December31,2010. We identified metformin users (the metformin group) and a set of diabetic comparators (the control group), individually matched to the metformin users by year of diabetes diagnosis, who had never used metformin. According to the drug dose, the metformin group was reassigned to2subgroups:subgroup1(>lg/d), subgroup2(≤1g/l). According to the applying time of metformin, the metformin group was reassigned to2subgroups:subgroup A (<5years), subgroup B (≥5years). The detection index included FPG, TC, TC, ALT, AST, BMI and so on. Cancer incidence was ascertained using cancer registries. Mortality data were obtained from death certificates. In the risk estimate analysis we calculated odds ratios (OR) for diagnosis of cancer, of the two groups using.ResultsA total of12156diabetes were initially identified, while, prospective data on6716metformin users and4950non metformin users were analyzed. There are no differences among sex, age, smoking history, course of disease, BMI, FPG, TC, TC, ALT and AST between the metformin group and the control group(P>0.05). From2000to2010, cancer was diagnosed among0.789%of6716metformin users compared with1.657%of4950 comparators, with median times to cancer of4.8and3.9years, respectively (P<0.001). The risk estimate analysis showed that metformin users was associated with a lower risk of incident cancer (Odds ratio0.472[95%CI0.334-0.668]). The cancer incidence of diabetes was nagetively related to the usage dose and application time of metformin. Patients whose metformin usage dose was<lg/d had a higher risk of incident cancer (odds ratio2.263[95%CI1.317-3.887]).Patients whose application time of metformin was<5years had a higher risk of incident cancer (odds ratio2.021[95%CI1.174-3.479]).ConclusionsMetformin use is associated with a reduced risk of cancer in people with type2diabetes, and metformin usage appears to be associated with improved overall survival of diabetic cancer patients. So, metformin is a promising anticancerous agent, which can be combined with chemotherapeutic agents to improve their sensitivity and their efficiency.