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Table 3 Relative risk estimations for breast cancer among insulin treatment groups and the evaluation of bias and power of the studies

From: Treatment with insulin (analogues) and breast cancer risk in diabetics; a systematic review and meta-analysis of in vitro, animal and human evidence

Author, year

Exposure of interest

Exposure comparison group

Cases/controls*** or cases/person-years**** in exposure group (number)

Cases/controls*** or cases/person-years****in comparison group (number)

Risk Ratio**

95 % CI

Risk of bias

Power

Any insulin-no insulin: hazard ratio

Carstensen et al., 2012 [43]

Insulin users

No insulin users

248/102,500

2,118/627,100

0.96

0.84, 1.09

Moderate

Adequate

Ferrara et al., 2011 [48]

Insulin users

No insulin users

NR

NR

1.0

0.9, 1.2

Moderate

Adequate

Neumann et al., 2012 [60]

Insulin users

No insulin users

NR/NR*

NR/NR*

0.86

0.81, 0.91

High

Adequate

Onitilo et al., 2014 [61]

Insulin users

No insulin users

NR/NR*

NR/NR*

0.84

0.58, 1.23

High

Too low

Any insulin-no insulin: odds ratio

Bodmer et al., 2010a [41]

Insulin users

No insulin users

43/131

262/1,022

NE

NE

High

Too low

Cleveland et al., 2012 [45]

Insulin users

No insulin users

20/16

50/49

1.15

0.40, 3.40

High

Too low

Any insulin-NIAD: hazard ratio

Currie et al., 2009a [6]

Insulin users

Metformin only

NR/12,640*

NR/34,847*

1.07

0.79, 1.44

Moderate

Too low

Redaniel et al., 2012a [62]

Insulin and NIAD users

Sulfonylurea only users

33/8,233.8

93/27,308.2

1.23

0.63, 2.38

Low

Too low

Redaniel et al., 2012b [62]

Insulin only users

Sulfonylurea only users

8/2,247.3

93/27,308.2

1.67

0.70, 3.99

Low

Too low

Vallarino et al., 2013****** [67]

Pioglitzone users, not using insulin

Insulin users, not using pioglitazone

181/29,721

113/13,680

0.85

0.67, 1.08

High

Low

Any insulin-NIAD: odds ratio

Hsieh et al., 2012 [53]

Insulin only users

Metformin only users

5/NR

19/NR

1.63

0.60, 4.40

High

Too low

Koro et al., 2007a [54]

Insulin and NIAD users

TZD users

13/52

83/449

0.71

0.36, 1.37

High

Too low

Koro et al., 2007b [54]

Insulin only users

TZD users

9/62

83/449

1.27

0.61, 2.67

High

Too low

Glargine-no glargine: hazard ratio

Bordeleau et al., 2014***** [42]

Glargine users

Standard care, not using glargine

28/11,620*

28/12,845*

1.15

0.67, 1.97

Low

Too low

Home and Lagarenne, 2009***** [52]

Glargine users

Any anti-diabetic drug, NPH in 20 studies

4/4,711

6/4,524

0.62

0.17, 2.18

Moderate

Too low

Rosenstock et al., 2009 [63]

Glargine users

NPH users

3/2,144

5/2,096

0.90

0.64, 1.26

Low

Too low

Chang et al., 2011***** [44]

Glargine users, not using int-/long-acting HI

Non-glargine int/long-acting HI users

6/6,558.8*

65/47,724.6*

0.53

0.21, 1.31

Moderate

Too low

Colhoun et al., 2009a [5]

Glargine plus non-glargine insulin users

Non-glargine insulin users

0/NR

29/9,667*

NE

NE

High

Too low

Colhoun et al., 2009b***** [5]

Glargine only users

Non-glargine insulin users

6/1,200*

29/9,667*

1.47

0.59, 3.64

High

Too low

Currie et al., 2009b***** [6]

Glargine users

Non-glargine insulin users

10/2,245*

38/8,102*

0.86

0.42, 1.75

Moderate

Too low

Fagot et al., 2013a***** [47]

Glargine users

Other int-/long-acting insulin only users

114/42,129*

40/14,082*

1.08

0.72, 1.62

High

Too low

Habel et al., 2013a**** * [51]

Glargine users

NPH insulin users

52/10,614.8

217/60,868.1

1.3

1.0, 1.8

Moderate

Too low

Habel et al., 2013b [51]

Glargine only users

NPH insulin users

33/6,402.4

217/60,868.1

1.3

0.9, 2.0

Moderate

Too low

Habel et al., 2013c [51]

Glargine and NPH insulin users

NPH insulin users

19/4,212.5

217/60,868.1

1.3

0.8, 2.0

Moderate

Too low

Kostev et al., 2012a***** [55]

Glargine users

NPH insulin users

NR

NR

0.93

0.68, 1.27

High

Too low

Lind et al., 2012a***** [56]

Glargine users

Non-glargine users

19/7,019.4

96/48,889.6*

1.54

0.90, 2.67

Moderate

Too low

Morden et al., 2011a [59]

Glargine plus non-glargine insulin users

Non-glargine insulin users

102/18,889*

333/65,294*

1.08

0.86, 1.36

High

Low

Morden et al., 2011b***** [59]

Glargine only users

Non-glargine insulin users

118/21,071*

333/65,294*

1.03

0.83, 1.29

High

Low

Ruiter et al., 2012a***** [64]

Glargine only users

Human insulin only users

11/6,875*

NR; IR=2.28*

1.65

1.10, 2.47

Moderate

Too low

Sturmer et al., 2013a **** [65]

Glargine users

NPH users

103/26,277

19/5,885

1.07

0.65, 1.75

Moderate

Too low

Suissa et al., 2011a***** [66]

Glargine users

Non-glargine insulin users

18/6,094

60/12,262

0.8

0.3, 2.1

Moderate

Too low

Pooled hazard ratio

Glargine

No glargine

  

1.04

0.91, 1.17

  

Glargine-no glargine: incidence rate ratio

Ljung et al., 2011a [57]

Glargine plus non-glargine insulin users

Non-glargine insulin users

59/25,033

283/101,419

1.04

0.77, 1.41

High

Low

Ljung et al., 2011b [57]

Glargine only users

Non-glargine insulin users

31/7,302

283/101,419

1.58

1.09, 2.29

High

Too low

Glargine-no glargine: odds ratio

Grimaldi-Bensouda et al., 2013a [49]

Glargine users

Non-glargine users

78/287

697/2,763*

1.04

0.76, 1.44

Low

Borderline

Grimaldi-Bensouda et al., 2013b [49]

Glargine users

Non-glargine insulin users

74/203

70/207

0.96

0.61, 1.53

Low

Too low

Grimaldi-Bensouda et al., 2013c [49]

Glargine users

Human insulin users

NR

NR

1.29

0.78, 2.13

Low

NE

Grimaldi-Bensouda et al., 2013d [49]

Glargine users

Aspart users

NR

NR

1.10

0.64, 1.89

Low

NE

Grimaldi-Bensouda et al., 2013e [49]

Glargine users

Lispro users

NR

NR

0.85

0.48, 1.50

Low

NE

Mannucci et al., 2010a [58]

Glargine users

Non-glargine insulin users

NR

NR

NE

NE

High

Too low

Determir-no determir: hazard ratio

Fagot et al., 2013b [47]

Determir users

Other int-/long-acting insulin only users

38/12,806*

116/43,131*

1.08

0.72, 1.62

High

Too low

Kostev et al., 2012b [55]

Detemir users

NPH insulin users

NR/789

NR/4,206

1.17

0.66, 2.06

High

Too low

Determir-no determir: incidence rate ratio

Dejgaard et al., 2009a [46]

Determir users

NPH users

1/2,252

0/1,420

NE

NE

Low

Too low

Dejgaard et al., 2009b [46]

Determir users

Glargine users

1/917

3/628

NR

NR

Low

Too low

Aspart-no aspart: odds ratio

Grimaldi-Bensouda et al., 2013f [55]

Aspart users

Non-aspart users

54/241

721/2,809*

0.95

0.64, 1.40

Low

Borderline

Lispro-no lispro: odds ratio

Grimaldi-Bensouda et al., 2013g [49]

Lispro users

Non-lispro users

46/133

729/2,917*

1.23

0.79, 1.92

Low

Borderline

Human insulin-no human insulin: hazard ratio

Fagot et al., 2013c [47]

Basal human insulin users

Other int-/long-acting insulin only users

15/5,813*

139/50,948*

1.03

0.56, 1.88

High

Too low

Gu et al., 2013 [50]

Human insulin users

No insulin users

4/6,188*

14/10,435*

0.33

0.10, 1.13

Moderate

Too low

Ruiter et al., 2012b [64]

Non-glargine insulin users

Human insulin only users

31/15,578*

NR; IR=2.28*

0.99

0.81, 1.20

Moderate

Too low

Human insulin-no human insulin: odds ratio

Grimaldi-Bensouda et al., 2013h [49]

Human insulin users

Non-human insulin users

59/260

716/2,790*

0.81

0.55, 1.20

Low

Borderline

  1. Bold values are significantly different. *Calculated using data provided (if not indicated directly these were taken from the table in the paper). **Risk estimates are adjusted for covariates as stated in Additional file 1: Table S3. Covariates used in the various analyses are the same within one study. ***Case–control studies. ****Cohort studies or randomized clinical trials. *****Included in meta-analysis. ******The exposure of interest is the exposure comparison group in this analysis. Studies are first ordered by type of exposure and then by type of risk estimate. Note: Hiesh 2012 is a cohort study but provided odds ratio estimates in the paper. Names of exposure groups are defined by the authors of the study. Several papers showed multiple risk estimates for the same exposure with different analytical approaches. For each study and exposure, the results from the least biased or best performed analyses are shown; showing hazard ratios, incidence rate ratios or odds ratios as applicable. Different exposure comparisons within one study are indicated by a,b,c etc. We choose to include the risk estimate that gave (in order of importance): 1) estimates for incident users was preferred over estimates for prevalent users; 2) as-treated analysis (during study period/follow up) was preferred over intention-to-treat analysis (during fixed period/at baseline); 3) estimates with the longest latency period were preferred. Estimates from statistical models adjusted for covariates were preferred over crude estimate. NR not reported, NE not estimated, HI human insulin, TZD Thiazolidinedione, NIAD non-insulin anti-diabetic drug, NPH Neutral Protamine Hagedorn, Int intermediate.