Publication Abstract

Authors: Chen L, Chubak J, Boudreau DM, Barlow WE, Weiss NS, Li CI

Title: Diabetes treatments and risks of adverse breast cancer outcomes among early stage breast cancer patients: A SEER-Medicare analysis.

Journal: Cancer Res :-

Date: 2017 Sep 21

Abstract: The widely prescribed diabetes medicine metformin has been reported to lower the risk of incident breast cancer, but it is unclear if it affects malignant progression after diagnosis. In this study, we conducted a retrospective cohort study using the linked Surveillance, Epidemiology and End-Results (SEER)-Medicare database. Women were included in the study if they were aged 66-80 years, newly diagnosed with stage I or II breast cancer, and enrolled in Medicare Parts A, B, and D during 2007-2011. Information on dispensed diabetes-related medications was obtained from Medicare Part D claims data. Our primary outcomes were second breast cancer events (SBCE), breast cancer recurrence, and breast cancer death. Time-varying Cox proportional hazard models were used to estimate hazard ratios and their 95% confidence intervals (CI). Among 14,766 women included in the study, 791 experienced SBCE, 627 had a recurrence, and 237 died from breast cancer. Use of metformin (n=2,558) was associated with 28% (95% CI: 0.57-0.92), 31% (95% CI: 0.53-0.90), and 49% (95% CI: 0.33-0.78) lower risks of a SBCE, breast cancer recurrence, and breast cancer death. Use of sulfonylureas or insulin was associated with 1.49 (95% CI: 1.00-2.23) and 2.58-fold (95%CI: 1.72-3.90) higher risks of breast cancer death. Further research may be warranted to determine if metformin is a preferred treatment for diabetes among breast cancer survivors and whether it benefits breast cancer patients without diabetes.