Table 1.
Risk Factors in the Ella Study, by Breast Cancer Tumor Subtype
| Luminal A n=571 | HER2+ n=225 | TNBC n=159 | |
|---|---|---|---|
| Age at diagnosis, y | |||
| <50 | 250(43.8) | 93 (41.3) | 93(58.5) |
| 50 to 59 | 169 (29.6) | 73 (32.4) | 30 (18.9) |
| ≥60 | 152 (26.6) | 59 (26.2) | 36 (22.6) |
| Mean ± SD | 52.3 ± 12.2 | 53.2 ± 12.2 | 50.1 ± 13.3 |
| Age at menarche, y | |||
| <13 | 261 (45.7) | 104 (46.2) | 64 (40.5) |
| ≥13 | 310 (54.3) | 121 (53.8) | 94 (59.5) |
| Unknown | 0 | 0 | 1 |
| Mean ± SD | 12.7 ± 1.6 | 12.7 ± 1.7 | 13.0 ± 1.7 |
| Parity | |||
| Nulliparous | 58 (10.2) | 25 (11.1) | 9 (5.7) |
| 1 to 2 children | 176 (30.8) | 74 (32.9) | 39 (24.5) |
| ≥3 children | 337 (59.0) | 126 (56.0) | 111 (69.8) |
| Mean ± SD (excludes nulliparous) | 3.5 ± 2.2 | 3.5 ± 2.1 | 3.7 ± 2.1 |
| Age at first full-term pregnancy, y | |||
| <21 | 201 (39.2) | 77 (38.5) | 68 (45.6) |
| 21–24 | 133 (25.9) | 55 (27.5) | 42 (28.2) |
| ≥25 | 179 (34.9) | 68 (34.0) | 39 (26.2) |
| Nulliparous | 58 | 25 | 9 |
| Unknown | 0 | 0 | 1 |
| Mean ± SD | 23.1 ± 5.6 | 23.0 ± 5.3 | 21.9 ± 4.9 |
| Time since last full-term pregnancy, y | |||
| >10 | 159 (64.4) | 53 (57.0) | 48 (60.0) |
| ≤10 | 88 (35.6) | 40 (43.0) | 32 (40.0) |
| Postmenopausal (or unknown) | 293 | 122 | 71 |
| Premenopausal but nulliparous | 31 | 10 | 8 |
| Mean ± SD | 13.5 ± 7.6 | 13.5 ± 8.2 | 12.1 ± 7.7 |
| Time from menarche to first pregnancy, y | |||
| <8 | 179 (34.9) | 71 (35.5) | 69 (46.6) |
| 8–12 | 172 (33.5) | 68 (34.0) | 49 (33.1) |
| ≥13 | 162 (31.6) | 61 (30.5) | 30 (20.3) |
| Nulliparous | 58 | 25 | 9 |
| Unknown | 0 | 0 | 2 |
| Mean ± SD | 10.3 ± 5.8 | 10.2 ± 5.5 | 8.9 ± 5.2 |
| Lifetime duration of breastfeeding, mo | |||
| Never | 134 (26.1) | 58 (29.0) | 23 (15.3) |
| Up to 12 | 188 (36.7) | 63 (31.5) | 52 (34.7) |
| >12 | 191 (37.2) | 79 (39.5) | 75 (50.0) |
| Nulliparous | 58 | 25 | 9 |
| Mean ± SD | 18.3 ± 28.7 | 21.5 ± 36.5 | 24.8 ± 34.9 |
| Breastfeeding duration per birth, mo | |||
| Never | 134 (26.1) | 58 (29.0) | 23 (15.3) |
| >0 to 5 | 206 (40.2) | 66 (33.0) | 60 (40.0) |
| >5 | 173 (33.7) | 76 (38.0) | 67 (44.7) |
| Nulliparous | 58 | 25 | 9 |
| Mean ± SD | 4.7 ± 6.5 | 5.1 ± 6.3 | 6.4 ± 7.4 |
| Duration of menstruation, y | |||
| 7.6–27.35 | 172 (32.4) | 59 (28.8) | 64 (42.4) |
| 27.4–33.45 | 174 (32.8) | 62 (30.2) | 60 (39.7) |
| 33.5–50.5 | 185 (34.8) | 84 (41.0) | 27 (17.9) |
| Periods never regular | 35 | 14 | 7 |
| Unknown | 5 | 6 | 1 |
| Mean ± SD | 30.1 ± 7.2 | 30.9 ± 6.4 | 27.5 ± 7.1 |
| Duration of menstruation, y | |||
| 0–25.23 | 150 (31.5) | 56 (30.8) | 58 (40.9) |
| 25.23–31.75 | 160 (33.6) | 55 (30.2) | 57 (40.1) |
| 31.85–50.5 | 166 (34.9) | 71 (39.0) | 27 (19.0) |
| Periods never regular | 35 | 14 | 7 |
| Unknown | 60 | 29 | 10 |
| Mean ± SD | 28.4 ± 7.5 | 28.8 ±6.9 | 25.8 ± 7.6 |
| Menopausal status at diagnosis | |||
| Premenopausal | 278 (49.2) | 103 (47.0) | 88 (55.7) |
| Postmenopausal | 287 (50.8) | 116 (53.0) | 70 (44.3) |
| Unknown | 6 | 6 | 1 |
| Age at menopause, y | |||
| <50 | 164 (57.1) | 68 (58.6) | 48 (68.6) |
| ≥50 | 123 (42.9) | 48 (41.4) | 22 (31.4) |
| Premenopausal at diagnosis | 278 | 103 | 88 |
| Unknown | 6 | 6 | 1 |
| Mean ± SD | 47.3 ± 6.7 | 47.7 ± 6.1 | 45.9 ± 7.1 |
| Hormone replacement therapy | |||
| Never | 490 (86.9) | 192 (85.7) | 142 (89.3) |
| Ever | 74 (13.1) | 32 (14.3) | 17 (10.7) |
| Unknown | 7 | 1 | 0 |
| Hormone contraceptive use | |||
| Never | 244 (42.8) | 102(45.3) | 78 (49.1) |
| Ever | 326 (57.2) | 123 (54.7) | 81 (50.9) |
| Unknown | 1 | 0 | 0 |
Abbreviations: SD, standard deviation; U.S., United States; HER2, human epidermal growth factor receptor 2; TNBC, triple negative breast cancer.
A
Textile categories; duration accounts for pregnancy. Excludes 56 women never having a regular period and 12 women with unknown age at menopause or menopausal status.
b
Tertile categories; duration accounts for pregnancy and breastfeeding. Excludes 56 women never having a regular period, 12 women with unknown age at menopause/menopausal status, and 87 women with unknown lifetime duration breastfeeding.