Impact of preexisting type 2 diabetes mellitus and antidiabetic drugs on all-cause and cause-specific mortality among Medicaid-insured women diagnosed with breast cancer.

Background: We investigated the influence preexisting type 2 diabetes mellitus (T2DM) and antidiabetic drugs have on all-cause and cause-specific mortality among Medicaid-insured women diagnosed with breast cancer.

Methods: 9221 women aged <64 years diagnosed with breast cancer and reported to the New York State (NYS) Cancer Registry from 2004 to 2016 were linked with Medicaid claims. Preexisting T2DM was determined by three diagnosis claims for T2DM with at least one claim prior to breast cancer diagnosis and a prescription claim for an antidiabetic drug within three months following breast cancer diagnosis. Estimated menopausal status was determined by age (premenopausal age <50; postmenopausal age ≥50). Hazard ratios (HR) and 95 % confidence intervals (95 %CI) were calculated with Cox proportional hazards regression, adjusting for confounders.

Results: Women with preexisting T2DM had greater all-cause (HR = 1.40; 95 %CI 1.21, 1.63), cancer-specific (HR = 1.24; 95 %CI 1.04, 1.47), and cardiovascular-specific (HR = 2.46; 95 %CI 1.54, 3.90) mortality hazard compared to nondiabetic women. In subgroup analyses, the association between T2DM and all-cause mortality was found among non-Hispanic White (HR 1.78 95 %CI 1.38, 2.30) and postmenopausal (HR = 1.47; 95 %CI 1.23, 1.77) women, but not among other race/ethnicity groups or premenopausal women. Additionally, compared to women prescribed metformin, all-cause mortality hazard was elevated among women prescribed sulfonylurea (HR = 1.44; 95 %CI 1.06, 1.94) or insulin (HR = 1.54; 95 %CI 1.12, 2.11).

Conclusion: Among Medicaid-insured women with breast cancer, those with preexisting T2DM have an increased mortality hazard, especially when prescribed sulfonylurea or insulin. Further research is warranted to determine the role antidiabetic drugs have on survival among women with breast cancer.