New Users of Metformin Are at Low Risk of Incident Cancer
A cohort study among people with type 2 diabetes
Article Figures & Tables
Figures
- Figure 1
Flowchart showing how metformin users and comparators were selected for the study.
- Figure 2
Kaplan-Meier plot with 95% CIs showing time to cancer among metformin users and comparators.
Tables
- Table 1
Baseline characteristics and results of Cox regression analysis for incidence of cancer among metformin users and comparators
Metformin users Comparators Diagnosed cancer Unadjusted Adjusted* Comparators 4,085 — 474 1.00 1.00 Metformin users — 4,085 297 0.46 (0.40–0.53) 0.63 (0.53–0.75) Sex Female 1,848 (45.9) 1,875 (45.2) 315 1.00 1.00 Male 2,237 (54.1) 2,210 (54.8) 456 1.26 (1.09–1.45) 1.37 (1.18–1.59) Age (years) 35–55 1,001 (24.5) 533 (13.1) 51 1.00 1.00 56–63 964 (23.6) 647 (15.8) 138 2.72 (1.97–3.75) 2.66 (1.92–3.68) 64–69 865 (21.2) 691 (16.9) 160 3.40 (2.48–4.67) 3.13 (2.27–4.32) 70–76 781 (19.1) 939 (23.0) 205 4.61 (3.39–6.28) 4.09 (2.98–5.61) 77–100 474 (11.6) 1,275 (31.2) 217 5.95 (4.37–8.12) 4.86 (3.51–6.73) Smoking status Current 577 (14.1) 558 (13.7) 109 1.00 1.00 Ex-smoker 1,015 (24.9) 866 (21.2) 177 0.99 (0.78–1.26) 0.77 (0.60–0.98) Never 1,637 (40.1) 1,411 (34.5) 271 0.87 (0.69–1.09) 0.75 (0.60–0.94) Not known 856 (21.0) 1,250 (30.6) 214 1.19 (0.94–1.51) 0.91 (0.72–1.16) Carstairs deprivation category 1 (least deprived) 224 (5.5) 206 (5.0) 46 1.00 1.00 2 805 (19.7) 902 (22.1) 162 0.75 (0.56–1.01) 0.74 (0.55–0.99) 3 1,129 (27.6) 1,171 (28.7) 223 0.80 (0.61–1.07) 0.82 (0.62–1.09) 4 458 (11.2) 488 (12.0) 99 0.78 (0.56–1.08) 0.81 (0.58–1.12) 5 521 (12.8) 457 (11.2) 77 0.66 (0.47–0.92) 0.69 (0.49–0.97) 6 603 (14.8) 579 (14.2) 106 0.71 (0.52–0.98) 0.79 (0.58–1.09) 7 (most deprived) 345 (8.5) 282 (6.9) 58 0.72 (0.50–1.04) 0.83 (0.58–1.19) BMI 30.7 ± 3.5 28.6 ± 3.1 — 0.93 (0.91–0.95) 0.98 (0.96–1.00) A1C (%) 7.9 ± 1.0 7.2 ± 1.2 — 0.77 (0.72–0.82) 0.91 (0.84–0.98) Insulin use No use 3,833 (93.8) 3,512 (86.0) 696 1.00 1.00 Use within 1 year 252 (6.2) 573 (14.0) 75 0.99 (0.85–1.15) 1.13 (0.97–1.33) Sulphonylurea use No use 2,196 (53.8) 1,996 (73.3) 483 1.00 1.00 Use within 3 months 1,889 (46.2) 1,089 (26.7) 288 1.00 (0.78–1.28) 1.12 (0.87–1.47) -
Data are n, n (%), means ± SD, or HR (95% CI).
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↵*Adjusted for all covariates.
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- Table 2
Unadjusted and adjusted HRs for secondary outcomes with adjusted HRs for incidence of cancer stratified by maximum prescribed dose and duration of follow-up with comparators as the reference category
n (%) Unadjusted Adjusted* Incidence of bowel cancer Comparators 76 (1.9) 1.00 1.00 Users 40 (1.0) 0.41 (0.28–0.61) 0.60 (0.38–0.94) Incidence of lung cancer Comparators 58 (1.4) 1.00 1.00 Users 35 (0.9) 0.49 (0.32–0.74) 0.70 (0.43–1.15) Incidence of breast cancer in women Comparators 41 (2.2) 1.00 1.00 Users 24 (1.3) 0.44 (0.26–0.73) 0.60 (0.32–1.10) Overall mortality Comparators 1,422 (34.8) 1.00 1.00 Users 609 (14.9) 0.32 (0.29–0.35) 0.42 (0.38–0.47) Mortality from cancer Comparators 248 (6.1) 1.00 1.00 Users 123 (3.0) 0.48 (0.39–0.60) 0.63 (0.49–0.81) Incidence of cancer <2 years follow-up* 2–4 years follow-up* >4 years follow-up* Maximum prescribed dose during follow-up (n) Low (1,017) 3.15 (1.92–5.18) 0.99 (0.44–2.25) 0.16 (0.06–0.44) Medium (2,090) 1.94 (1.20–3.13) 0.51 (0.31–0.82) 0.40 (0.27–0.60) High (978) 2.76 (0.56–13.45) 0.28 (0.12–0.70) 0.15 (0.09–0.25) -
Data are HR (95% CI) unless otherwise indicated.
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↵*Adjusted for age, sex, smoking, deprivation, BMI, A1C, insulin use, and sulphonylurea use.
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In this Issue
September 2009, 32(9)
