Metformin may reduce breast cancer risk in Taiwanese women with type 2 diabetes
Menée à partir de données taïwanaises portant sur 476 282 patientes présentant un diabète sucré de type 2 diagnostiqué entre 1998 et 2002, cette étude met en évidence une association entre l'utilisation de la metformine, un antidiabétique oral, et une réduction du risque de cancer du sein
Whether metformin therapy affects breast cancer risk in Asian patients with type 2 diabetes mellitus (T2DM) has not been investigated. The reimbursement databases of Taiwanese female patients with a new diagnosis of T2DM between 1998 and 2002 (n = 476,282) were retrieved from the National Health Insurance for follow-up of breast cancer until the end of 2009. Metformin was treated as a time-dependent variable; and of these patients, 285,087 were never-users and 191,195 were ever-users. A time-dependent approach was used to calculate breast cancer incidence and estimate hazard ratios by Cox regression for ever-users, never-users, and subgroups of metformin exposure (tertiles of cumulative duration and cumulative dose). During follow-up, 2,412 (1.26 %) metformin ever-users and 9,322 (2.10 %) never-users developed breast cancer, representing an incidence of 201.08 and 535.88 per 100,000 person-years, respectively. The overall multivariable-adjusted hazard ratio (95 % confidence intervals) for ever- versus never-users was 0.630 (0.597–0.665). The multivariable-adjusted hazard ratios for the first, second, and third tertiles of cumulative duration of metformin therapy were 1.122 (1.043–1.207), 0.754 (0.692–0.820), and 0.280 (0.253–0.310), respectively, (P-trend <0.0001); and 1.099 (1.021–1.182), 0.664 (0.611–0.723), and 0.311 (0.281–0.344), respectively, (P-trend <0.0001), for cumulative dose of metformin. Metformin use is associated with a decreased risk of breast cancer.