Table 1.
Patient Demographics and Clinical Characteristics by Study Group
| Characteristic | Metformin Group* |
Nonmetformin Group* |
Nondiabetic Group* |
P | |||
|---|---|---|---|---|---|---|---|
| No. | % | No. | % | No. | % | ||
| Age at diagnosis, years | < .001 | ||||||
| Median | 57.5 | 57 | 49 | ||||
| Range | 41-75 | 34-87 | 21-83 | ||||
| < 50 | 15 of 68 | 22 | 20 of 87 | 23 | 1,263 of 2,374 | 53 | |
| ≥ 50 | 53 of 68 | 78 | 67 of 87 | 77 | 1,111 of 2,374 | 47 | |
| Menopausal status at diagnosis | < .001 | ||||||
| Premenopausal | 15 of 68 | 22 | 14 of 87 | 16 | 1,169 of 2,363 | 49 | |
| Postmenopausal | 53 of 68 | 78 | 73 of 87 | 84 | 1,194 of 2,363 | 51 | |
| Hemoglobin A1c level† | .52 | ||||||
| Median | 7.3 | 7.8 | — | ||||
| Range | 5.1-13.7 | 5.4-12.7 | — | ||||
| BMI | .001 | ||||||
| Median | 33.8 | 32.8 | 26.9 | ||||
| Range | 22.5-61.7 | 15.9-57.9 | 16.3-66.0 | ||||
| Category | |||||||
| Normal/underweight, ≤ 25 | 4 of 68 | 6 | 12 of 85 | 14 | 841 of 2,283 | 37 | |
| Overweight, 25 to < 30 | 16 of 68 | 24 | 24 of 85 | 28 | 724 of 2,283 | 32 | |
| Obese, ≥ 30 | 48 of 68 | 71 | 49 of 85 | 58 | 718 of 2,283 | 31 | |
| Clinical stage | .18 | ||||||
| I | 0 of 68 | 0 | 1 of 87 | 1 | 116 of 2,363 | 5 | |
| II | 38 of 68 | 56 | 49 of 87 | 56 | 1,309 of 2,363 | 55 | |
| III | 30 of 68 | 44 | 37 of 87 | 43 | 937 of 2,363 | 40 | |
| Nuclear grade | .28 | ||||||
| 1 | 4 of 66 | 6 | 0 of 86 | 0 | 77 of 2,314 | 3 | |
| 2 | 23 of 66 | 35 | 28 of 86 | 33 | 728 of 2,314 | 31 | |
| 3 | 39 of 66 | 59 | 58 of 86 | 67 | 1,509 of 2,314 | 65 | |
| ER/PR status | .36 | ||||||
| Both negative | 30 of 68 | 44 | 31 of 87 | 36 | 848 of 2,374 | 36 | |
| Either positive | 38 of 68 | 56 | 56 of 87 | 64 | 1,526 of 2,374 | 64 | |
| HER-2 status | .23 | ||||||
| Negative | 47 of 68 | 69 | 69 of 85 | 81 | 1,760 of 2,334 | 75 | |
| Positive | 21 of 68 | 31 | 16 of 85 | 19 | 574 of 2,334 | 25 | |
| Lymphovascular invasion | .80 | ||||||
| No | 48 of 67 | 72 | 55 of 82 | 67 | 1,548 of 2,282 | 68 | |
| Yes | 19 of 67 | 28 | 27 of 82 | 33 | 732 of 2,282 | 32 | |
| Insulin use | .02 | ||||||
| No | 57 of 68 | 84 | 58 of 87 | 67 | — | ||
| Yes | 11 of 68 | 16 | 29 of 87 | 33 | — | ||
| Thiazolidinedione use | .36 | ||||||
| No | 48 of 68 | 71 | 67 of 87 | 77 | — | ||
| Yes | 20 of 68 | 29 | 20 of 87 | 23 | — | ||
| Taxane use | .01 | ||||||
| No | 9 of 68 | 13 | 14 of 87 | 16 | 597 of 2,374 | 25 | |
| Yes | 59 of 68 | 87 | 73 of 87 | 84 | 1,777 of 2,374 | 75 | |
Abbreviations: BMI, body mass index; ER, estrogen receptor; PR, progesterone receptor; HER-2, human epidermal growth factor receptor 2.
*
Because of rounding, figures may not add up to 100%.
†
Based on available data of 29 patients in the metformin group and 34 patients in the nonmetformin group.