Table 3.

Use of medications for T2D in relation to ER+ and ER− breast cancer incidence

ER+ breast cancerER− breast cancer
CasesMV HR (95% CI)CasesMV HR (95% CI)
No diabetes841Reference426Reference
T2D medication usea
 No130.93 (0.54, 1.61)122.03 (1.13–3.62)
 Yes581.07 (0.81, 1.40)291.30 (0.88–1.92)
Type of medicationa
 Metformin370.92 (0.65–1.28)211.26 (0.80–1.98)
 All other types211.49 (0.96–2.32)81.41 (0.69–2.86)
  • NOTE: HRs adjusted for age, BMI, BMI at age 18, parity, age at first birth, age at menarche, duration of oral contraceptive use, duration of menopausal hormone use, and first degree family history of breast cancer.

  • aMedications reported in the three most recent follow-up questionnaires, covering period of approximately 6 years prior to breast cancer diagnosis (for cases) or end of follow-up (noncases).