Table 1.
Selected characteristics of study participants from the BREAST-Stamp Project, who were referred for an image-guided breast biopsy, stratified by the training and testing sets (n = 852)
| Characteristic | Overall (N = 852) | Training (N = 588) | Testing (N = 264) | P-value* | |||
|---|---|---|---|---|---|---|---|
| n | % | n | % | n | % | ||
| Age at ipsilateral mammogram (years) | 0.85 | ||||||
| <45 | 175 | 20.5 | 119 | 20.2 | 56 | 21.2 | |
| 45–49 | 217 | 25.5 | 152 | 25.9 | 65 | 24.6 | |
| 50–54 | 202 | 23.7 | 142 | 24.2 | 60 | 22.7 | |
| 55–59 | 145 | 17.0 | 95 | 16.2 | 50 | 18.9 | |
| 60+ | 113 | 13.3 | 80 | 13.6 | 33 | 12.5 | |
| Mean (SD) | 50.8 (6.9) | 50.8 (6.9) | 50.7 (6.8) | 0.91** | |||
| Race | 0.81 | ||||||
| White, non Hispanic | 778 | 91.3 | 536 | 91.2 | 242 | 91.7 | |
| Other | 74 | 8.7 | 52 | 8.8 | 22 | 8.3 | |
| Education level | 0.70 | ||||||
| <High school | 14 | 1.7 | 9 | 1.6 | 5 | 2.0 | |
| High school graduation | 132 | 16.0 | 95 | 16.7 | 37 | 14.6 | |
| College/graduation school degree | 678 | 82.3 | 466 | 81.8 | 212 | 83.5 | |
| BMI (kg/m2) | 0.22 | ||||||
| <25 | 427 | 50.4 | 283 | 48.4 | 144 | 54.8 | |
| 25-<30 | 212 | 25.0 | 153 | 26.2 | 59 | 22.4 | |
| 30+ | 209 | 24.7 | 149 | 25.5 | 60 | 22.8 | |
| Mean (SD) | 26.7 (6.3) | 26.8 (6.2) | 26.6 (6.5) | 0.43† | |||
| Age at menarche (years) | 0.41 | ||||||
| ≤12 | 326 | 38.9 | 216 | 37.2 | 110 | 42.8 | |
| 13 | 322 | 38.4 | 233 | 40.1 | 89 | 34.6 | |
| 14 | 114 | 13.6 | 80 | 13.8 | 34 | 13.2 | |
| 15+ | 76 | 9.1 | 52 | 9.0 | 24 | 9.3 | |
| Age at first birth (years) | 0.54 | ||||||
| Nulliparous | 189 | 22.3 | 134 | 22.9 | 55 | 21.2 | |
| <25 | 269 | 31.8 | 193 | 32.9 | 76 | 29.2 | |
| 25–30 | 202 | 23.9 | 135 | 23.0 | 67 | 25.8 | |
| 30+ | 186 | 22.0 | 124 | 21.2 | 62 | 23.9 | |
| Menopausal status | 0.89 | ||||||
| Premenopausal | 472 | 58.1 | 326 | 58.2 | 146 | 57.7 | |
| Postmenopausal | 341 | 41.9 | 234 | 41.8 | 107 | 42.3 | |
| Menopausal hormone therapy use | 0.88 | ||||||
| Never | 719 | 86.1 | 497 | 86.0 | 222 | 86.4 | |
| Ever | 116 | 13.9 | 81 | 14.0 | 35 | 13.6 | |
| First degree family history of breast cancer | 0.45 | ||||||
| 0 | 636 | 77.0 | 439 | 77.6 | 197 | 75.8 | |
| 1 | 167 | 20.2 | 114 | 20.1 | 53 | 20.4 | |
| 2+ | 23 | 2.8 | 13 | 2.3 | 10 | 3.9 | |
| Breast biopsy prior to enrollment | 0.54 | ||||||
| No | 580 | 68.9 | 404 | 69.5 | 176 | 67.4 | |
| Yes | 262 | 31.1 | 177 | 30.5 | 85 | 32.6 | |
| Global FGV (%)c | 0.55 | ||||||
| ≤34.4 (%) | 439 | 51.5 | 307 | 52.2 | 132 | 50.0 | |
| >34.4 (%) | 413 | 48.5 | 281 | 47.8 | 132 | 50.0 | |
| Median (Range) | 34.4 (0.6, 99.5) | 34.4 (0.6, 99.5) | 36.2, (1.4, 99.3) | ||||
| Localized FGV (%)c | 0.21 | ||||||
| ≤40 (%) | 406 | 50.7 | 289 | 52.2 | 117 | 47.4 | |
| >40 (%) | 395 | 49.3 | 265 | 47.8 | 130 | 52.6 | |
| Median (Range) | 40.0 (0, 100) | 39.8 (0, 100) | 43.3 (0, 100) | ||||
| Biopsy type | 0.82b | ||||||
| Ultrasound-guided (14-guage) | 445 | 52.2 | 309 | 52.6 | 136 | 51.5 | |
| Stereotactic-guided (9-guage) | 406 | 47.7 | 279 | 47.5 | 127 | 48.1 | |
| Both | 1 | 0.1 | 0 | 0.0 | 1 | 0.4 | |
| BI-RADS mammography assessment | 0.89 | ||||||
| Probably benign finding | 47 | 5.9 | 32 | 5.8 | 15 | 6.1 | |
| Suspicious abnormality | 670 | 83.7 | 463 | 83.4 | 207 | 84.2 | |
| Highly suggestive of malignancy | 84 | 10.5 | 60 | 10.8 | 24 | 9.8 | |
| Pathologic diagnosisa# | 0.23 | ||||||
| Benign non-proliferative | 282 | 33.1 | 190 | 32.3 | 92 | 34.9 | |
| Proliferative without atypia | 316 | 37.1 | 215 | 36.6 | 101 | 38.3 | |
| Proliferative with atypia | 57 | 6.7 | 44 | 7.5 | 13 | 4.9 | |
| In-situ (LCIS or DCIS) | 76 | 8.9 | 48 | 8.2 | 28 | 10.6 | |
| Invasive breast cancer | 121 | 14.2 | 91 | 15.5 | 30 | 11.4 | |
| Characteristic (per biopsy target, n = 1036 biopsies) | |||||||
| Biopsy type | 0.63b | ||||||
| Ultrasound-guided (14-guage) | 566 | 54.6 | 372 | 54.2 | 194 | 55.6 | |
| Stereotactic-guided (9-guage) | 469 | 45.3 | 315 | 45.9 | 154 | 44.1 | |
| Both | 1 | 0.1 | 0 | 0.0 | 1 | 0.3 | |
| Pathologic diagnosis# | 0.39 | ||||||
| Benign non-proliferative | 373 | 36.0 | 242 | 35.2 | 131 | 37.5 | |
| Proliferative without atypia | 369 | 35.6 | 242 | 35.2 | 127 | 36.4 | |
| Proliferative with atypia | 68 | 6.6 | 52 | 7.6 | 16 | 4.6 | |
| In-situ (LCIS or DCIS) | 83 | 8.0 | 53 | 7.7 | 30 | 8.6 | |
| Invasive breast cancer | 143 | 13.8 | 98 | 14.3 | 45 | 12.9 | |
BMI body mass index, DCIS ductal carcinoma in situ, FGV fibroglandular volume, LCIS lobular carcinoma in situ, SD standard deviation
Missing data were excluded from percentage calculations and statistical comparisons: 28 for education levels, 4 BMI, 14 age at menarche, 6 age at first birth, 39 menopausal status, 17 menopausal hormone therapy use, 26 first degree family history of breast cancer, 10 breast biopsy prior to enrollment, 51 percent volumetric local density (biopsy radius 0–2 mm), 51 BI-RADS mammography assessment
*P-values from Chi-Square test except where noted
**P-value from two-sample t-test
†P-values from Kruskal–Wallis test
aAmong women with multiple biopsies, this was the worst pathologic diagnosis
bOne woman from the test group who had both biopsy types was excluded from the Chi-square test
cThe median cut points of breast density were determined among the training population and were consistent among all 852 women
#Benign non-proliferative diagnosis includes non-proliferative fibrocystic change and other benign and discrete entities; Proliferative without atypia includes ductal hyperplasia and sclerosing adensosis; Proliferative with atypia includes atypical ductal and lobular hyperplasia