Table 5.

Risk of adverse breast cancer outcomes by diabetes treatment stratified by time of initiation

All womenSBCERecurrenceBreast cancer death
n = 11,494n = 537n = 414n = 134
n (%)an (%)aHRb (95% CI)n (%)aHRb (95% CI)n (%)aHRb (95% CI)
Metformin
 Never users9,277 (80.7)438 (81.6)Reference338 (81.6)Reference110 (82.1)Reference
 Continuous user1,463 (12.7)62 (11.5)0.77 (0.55–1.06)44 (10.6)0.66 (0.45–0.96)15 (11.2)0.41 (0.22–0.74)
 Began use after cancer diagnosis484 (4.2)21 (3.9)0.83 (0.49–1.41)19 (4.6)0.93 (0.54–1.62)c0.61 (0.22–1.71)
Sulfonylurea
 Never users10,010 (87.1)457 (85.1)Reference351 (84.8)Reference100 (74.6)Reference
 Continuous user976 (8.5)50 (9.3)1.03 (0.73–1.45)38 (9.2)0.99 (0.67–1.47)18 (13.4)1.18 (0.65–2.15)
 Began use after cancer diagnosis289 (2.5)21 (3.9)1.48 (0.88–2.50)18 (4.3)1.72 (0.99–2.96)c3.08 (1.53–6.20)
Insulin
 Never users10,625 (92.4)473 (88.1)Reference359 (86.7)Reference106 (79.1)Reference
 Continuous user519 (4.5)26 (4.8)1.08 (0.70–1.68)22 (5.3)1.22 (0.75–1.99)14 (10.4)2.14 (1.14–4.00)
 Began use after cancer diagnosis301 (2.6)35 (6.5)1.97 (1.25–3.13)31 (7.5)2.45 (1.52–3.96)12 (9.0)3.37 (1.73–6.58)
Other diabetes treatments
 Never users10,296 (89.6)473 (88.1)Reference366 (88.4)Reference115 (85.8)Reference
 Continuous user643 (5.6)34 (6.3)0.99 (0.66–1.47)24 (5.8)0.82 (0.51–1.32)12 (9.0)0.90 (0.47–1.72)
 Began use after cancer diagnosis255 (2.2)15 (2.8)0.82 (0.41–1.60)c0.78 (0.36–1.69)c0.55 (0.17–1.79)
  • aAnalyses were restricted to women enrolled in Medicare Part A/B/D at least 1 year prior to cancer diagnosis. Counts and percentages reflect ever use after cancer diagnosis, which was defined as having at least one prescription of a given drug after the initial cancer diagnosis. Numbers may not add up to the column total and percentages may not add up to 100% as those who stopped using the treatment after cancer were dropped from the analyses on that particular type of treatment.

  • bHRs 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 hormone therapy (time-varying), hypertension, and diabetes.

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