Table 4.

Risk of adverse breast cancer outcomes among treated diabetic women, 2007–2011a

Ever use after breastAllSBCERecurrenceBreast cancer death
cancer diagnosisnbnbHRc (95% CI)nbHRc (95% CI)nbHRc (95% CI)
Among all treated diabetic women (n = 3,189)
 Metformin
  No932 (29.2)71 (38.8)Reference58 (40.3)Reference40 (58.0)Reference
  Yes2,257 (70.8)112 (61.2)0.62 (0.46–0.83)86 (59.7)0.58 (0.41–0.81)29 (42.0)0.34 (0.21–0.55)
 Sulfonylureas
  No1,585 (49.7)82 (44.8)Reference62 (43.1)Reference28 (40.6)Reference
  Yes1,604 (50.3)101 (55.2)1.04 (0.78–1.40)82 (56.9)1.11 (0.80–1.55)41 (59.4)1.34 (0.82–2.17)
 Insulin
  No2,138 (67.0)106 (57.9)Reference78 (54.2)Reference34 (49.3)Reference
  Yes1,051 (33.0)77 (42.1)1.15 (0.84–1.57)66 (45.8)1.27 (0.90–1.80)35 (50.7)2.42 (1.50–3.91)
 Other diabetes treatments
  No2,025 (63.5)112 (61.2)Reference92 (63.9)Reference47 (68.1)Reference
  Yes1,164 (36.5)71 (38.8)0.77 (0.56–1.06)52 (36.1)0.68 (0.47–0.97)22 (31.9)0.73 (0.44–1.23)
Among all treated diabetic women excluding insulin users (n = 2,138)
 Metformin
  No418 (19.6)29 (27.4)Reference23 (29.5)Reference15 (44.1)Reference
  Yes1,720 (80.4)77 (72.6)0.58 (0.39–0.88)55 (70.5)0.53 (0.33–0.87)19 (55.9)0.37 (0.18–0.73)
 Sulfonylurea
  No1,038 (48.6)44 (41.5)Reference33 (42.3)Reference12 (35.3)Reference
  Yes1,100 (51.4)62 (58.5)1.15 (0.78–1.69)45 (57.7)1.12 (0.71–1.76)22 (64.7)1.76 (0.86–3.60)
 Other diabetes treatments
  No1,397 (65.3)62 (58.5)Reference48 (61.5)ReferencedReference
  Yes741 (34.7)44 (41.5)0.82 (0.54–1.25)30 (38.5)0.67 (0.40–1.10)d0.85 (0.41–1.78)
Among all treated diabetic women who were only using one diabetes treatment (n = 1,803)
 Metformin930 (51.6)31 (34.8)Reference25 (35.2)Reference
 Sulfonylureas368 (20.4)24 (27.0)1.99 (1.14–3.46)21 (29.6)2.12 (1.16–3.89)
 Insulin337 (18.7)25 (28.1)2.34 (1.35–4.06)19 (26.8)2.25 (1.21–4.21)
 Other diabetes treatments168 (9.3)d1.84 (0.86–3.94)d1.49 (0.60–3.70)
  • aSubsets of women were created in a time-varying fashion such that women entered the cohort when they first filled a prescription of diabetes treatment. For analyses among women only using one treatment, the users of each diabetes treatment were also defined in a similar time-varying fashion and would be censored when they started a second diabetes treatment.

  • bEver use was defined as having at least one prescription of a given drug after diagnosis for the purpose of presenting number of users, but the Cox models defined ever use as time-varying such that at risk time before one becomes a user contributes to the nonuser category. Counts of monotherapy users were women exclusively used one medication for at least some time (those who later used another medication were included in the counts but censored in the Cox model).

  • cHRs were adjusted for age at diagnosis, year of diagnosis, AJCC stage, ER/PR status, receipt of complete first course treatment (yes vs. no), receipt of any chemotherapy (yes vs. no), use of adjuvant hormone therapy (time-varying), and hypertension.

  • dCannot be displayed due to restrictions regarding the publication of small cells in the data use agreement.