Table 1.
Reproductive and clinical characteristics of premenopausal women, by country
| Characteristic | USA (n = 269) |
Mexico (n = 145) |
Spain (n = 213) |
|---|---|---|---|
| Time since last full-term pregnancy (y), n (%) | |||
| > 10 | 163 (60.6) | 96 (66.2) | 153 (71.8) |
| ≤ 10 | 106 (39.4) | 49 (33.8) | 60 (28.2) |
| Mean ± SD | 13.1 ± 7.8 | 13.8 ± 7.3 | 15.5 ± 8.1 |
| Total full-term pregnancies, n (%) | |||
| 1–2 | 119 (44.2) | 56 (38.6) | 177 (83.1) |
| 3+ | 150 (55.8) | 89 (61.4) | 36 (16.9) |
| Mean ± SD | 2.8 ± 1.3 | 3.0 ± 1.4 | 1.9 ± 0.7 |
| Age at first full-term pregnancy (y), n (%) | |||
| ≤ 23 | 169 (62.8) | 83 (57.2) | 97 (45.5) |
| > 23 | 100 (37.2) | 62 (42.8) | 116 (54.5) |
| Mean ± SD | 22.5 ± 5.4 | 23.0 ± 5.3 | 25.1 ± 5.4 |
| Age at last full-term pregnancy (y), n (%) | |||
| ≤ 30 | 149 (55.4) | 68 (46.9) | 122 (57.3) |
| > 30 | 120 (44.6) | 77 (53.1) | 91 (42.7) |
| Mean ± SD | 29.7 ± 5.7 | 30.5 ± 5.2 | 29.6 ± 5.9 |
| Interval between first and last pregnancy (y) | |||
| Mean ± SD (if parity > 1) | 8.5 ± 5.5 | 8.5 ± 5.3 | 6.4 ± 4.7 |
| Lifetime breastfeedinga (mo), n (%) | |||
| Never | 79 (29.4) | 16 (11.0) | 69 (32.6) |
| ≤ 12 | 115 (42.8) | 60 (41.4) | 113 (53.3) |
| > 12 | 75 (27.9) | 69 (47.6) | 30 (14.2) |
| Mean ± SD | 11.5 ± 16.2 | 21.5 ± 29.2 | 6.4 ± 9.8 |
| Age at menarche (y) | |||
| Mean ± SD | 12.6 ± 1.7 | 12.8 ± 1.5 | 12.8 ± 1.6 |
| Hormone contraceptive use, n (%) | |||
| Never | 84 (31.2) | 45 (31.0) | 82 (38.5) |
| Ever | 185 (68.8) | 100 (69.0) | 131 (61.5) |
| Age at diagnosis (y), n (%) | |||
| ≤ 45 | 163 (60.6) | 69 (47.6) | 101 (47.4) |
| > 45 | 106 (39.4) | 76 (52.4) | 112 (52.6) |
| Mean ± SD | 42.8 ± 6.4 | 44.3 ± 7.0 | 44.9 ± 5.1 |
| Family history of breast cancerb, n (%) | |||
| No | 225 (84.6) | 127 (88.8) | 182 (85.9) |
| Yes | 41 (15.4) | 16 (11.2) | 30 (14.2) |
| Tumor subtype, n (%) | |||
| HR+/HER2− | 164 (61.0) | 80 (55.2) | 149 (70.0) |
| HER2+ | 59 (21.9) | 33 (22.8) | 40 (18.8) |
| TNBC | 46 (17.1) | 32 (22.1) | 24 (11.3) |
| Tumor markers, n (%) | |||
| ER+ | 185 (68.8) | 82 (56.6) | 175 (82.2) |
| PR+ | 173 (64.3) | 85 (58.6) | 155 (72.8) |
| HER2+ | 59 (21.9) | 33 (22.8) | 40 (18.8) |
a
Missing data for lifetime breastfeeding (Spain, n = 1)
b
Family history of breast cancer in a first-degree relative; missing data (USA, n = 3; Mexico, n = 2; Spain, n = 1)