Table 1 Distribution of risk factors and clinicopathological characteristics by tumor subtype
Characteristic | Overall (%) | A-like (N = 1016/34%) | % | B-like (N = 989/33%) | % | HER2-enriched (N = 387/13%) | % | Triple-neg. (N = 620/20%) | % | P valuea |
|---|---|---|---|---|---|---|---|---|---|---|
Age, yrs | ||||||||||
 Mean (range) | 51.6 (19, 91) | 52.6 (24–90) |  | 51.1 (19, 90) |  | 51.6 (23, 91) |  | 51.5 (21, 87) |  |  |
  < 35 | 180 (5) | 47 | 4.6 | 49 | 5.0 | 26 | 6.7 | 40 | 6.5 | 0.01 |
 35–45 | 711 (21) | 192 | 18.9 | 219 | 22.1 | 76 | 19.7 | 144 | 23.2 |  |
 45–55 | 1204 (36) | 368 | 36.2 | 366 | 37.0 | 136 | 35.1 | 203 | 32.7 |  |
 55–65 | 806 (24) | 241 | 23.7 | 246 | 24.9 | 105 | 27.1 | 143 | 23.1 |  |
 65–75 | 364 (11) | 135 | 13.3 | 90 | 9.1 | 35 | 9.1 | 65 | 10.5 |  |
  > 75 | 90 (3) | 33 | 3.3 | 19 | 1.9 | 9 | 2.3 | 25 | 4.0 |  |
Ethnicity | ||||||||||
 Chinese | 1626 (48) | 567 | 55.8 | 435 | 44 | 180 | 46.5 | 275 | 44.4 | < 0.0001 |
 Malay | 801 (24) | 204 | 20.1 | 263 | 26.6 | 104 | 26.9 | 155 | 25 |  |
 Native | 928 (28) | 245 | 24.1 | 291 | 29.4 | 103 | 26.6 | 190 | 30.6 |  |
Menarche | ||||||||||
  ≤ 12 yrs | 1105 (33) | 344 | 34.1 | 326 | 33.2 | 118 | 30.8 | 190 | 30.9 | 0.20 |
 13 yrs | 1117 (34) | 318 | 31.5 | 340 | 34.7 | 148 | 38.6 | 201 | 32.7 |  |
 14 yrs | 548 (16) | 163 | 16.2 | 167 | 17 | 60 | 15.7 | 111 | 18 |  |
  ≥ 15 yrs | 559 (17) | 184 | 18.2 | 148 | 15.1 | 57 | 14.9 | 113 | 18.4 |  |
Menopause | ||||||||||
  ≤ 50 yrs | 428 (29) | 146 | 32.7 | 128 | 29.7 | 38 | 23.2 | 87 | 31.6 | 0.14 |
  > 50 yrs | 1031 (71) | 301 | 67.3 | 303 | 70.3 | 126 | 76.8 | 188 | 68.4 |  |
Parity | ||||||||||
 Nulliparous | 745 (22) | 242 | 23.8 | 224 | 22.6 | 77 | 19.9 | 128 | 20.6 | 0.29 |
 Parous | 2601 (78) | 774 | 76.2 | 765 | 77.4 | 310 | 80.1 | 492 | 79.4 |  |
Age at FFPb, yrs | ||||||||||
  < 21 | 466 (18) | 116 | 15 | 158 | 20.7 | 54 | 17.4 | 95 | 19.3 | 0.02 |
 21–24.9 | 1011 (39) | 284 | 36.7 | 287 | 37.5 | 129 | 41.6 | 199 | 40.5 |  |
 25–30 | 864 (33) | 275 | 35.5 | 248 | 32.4 | 103 | 33.2 | 154 | 31.4 |  |
  > 30 | 259 (10) | 99 | 12.8 | 72 | 9.4 | 24 | 7.7 | 43 | 8.7 |  |
Breastfeeding | ||||||||||
 No | 377 (14) | 133 | 17.2 | 103 | 13.5 | 31 | 10 | 64 | 13 | 0.01 |
 Yes | 2224 (86) | 641 | 82.9 | 662 | 86.5 | 279 | 90 | 428 | 87 |  |
Breastfeeding duration | ||||||||||
  < 6 months | 927 (52) | 285 | 54.2 | 280 | 51.8 | 111 | 49.6 | 175 | 51.3 | 0.40 |
 6–10 months | 374 (21) | 112 | 21.3 | 122 | 22.6 | 48 | 21.4 | 62 | 18.2 |  |
  > 10 months | 489 (27) | 129 | 24.5 | 138 | 25.6 | 65 | 29.0 | 104 | 30.5 |  |
BMI, kg/m2 | ||||||||||
  < 18.5 | 1253 (39) | 373 | 37.8 | 336 | 35.1 | 163 | 43.7 | 240 | 40.2 | 0.03 |
 18.5–24.9 | 565 (17) | 160 | 16.2 | 172 | 18 | 68 | 18.2 | 114 | 19.1 |  |
 25–29.9 | 998 (31) | 317 | 32.2 | 301 | 31.4 | 104 | 27.9 | 177 | 29.6 |  |
  ≥ 30 | 433 (13) | 136 | 13.8 | 148 | 15.5 | 38 | 10.2 | 66 | 11.1 |  |
Family history | ||||||||||
 No | 2835 (86) | 840 | 84 | 854 | 87.8 | 338 | 88 | 516 | 84.9 | 0.05 |
 Yes | 468 (14) | 160 | 16 | 119 | 12.2 | 46 | 12 | 92 | 15.1 |  |
Histological grade | ||||||||||
 Well diff. | 365 (11) | 212 | 20.9 | 67 | 6.8 | 10 | 2.6 | 27 | 4.4 | < 0.0001 |
 Moderately diff. | 1790 (55) | 781 | 76.9 | 442 | 44.7 | 180 | 46.5 | 238 | 38.4 |  |
 Poorly diff. | 1123 (34) | – | – | 473 | 47.8 | 192 | 49.6 | 344 | 55.5 |  |
Stage | ||||||||||
 I | 454 (14) | 222 | 22.1 | 100 | 10.3 | 34 | 8.9 | 61 | 10 | < 0.0001 |
 II | 1353 (42) | 444 | 44.2 | 395 | 40.6 | 136 | 35.6 | 249 | 40.9 |  |
 III | 1005 (31) | 241 | 24 | 330 | 33.9 | 150 | 39.3 | 203 | 33.3 |  |
 IV | 421 (13) | 78 | 7.8 | 139 | 14.3 | 57 | 14.9 | 91 | 14.9 |  |
Tumor size | ||||||||||
  < 2 cm | 2137 (64) | 761 | 75.6 | 620 | 63.3 | 210 | 54.7 | 353 | 57.8 | < 0.0001 |
 2–5 cm | 522 (16) | 121 | 12 | 150 | 15.3 | 83 | 21.6 | 104 | 17 |  |
  > 5 cm | 660 (20) | 125 | 12.4 | 209 | 21.4 | 91 | 23.7 | 154 | 25.2 |  |
Node status | ||||||||||
 0 | 1517 (46) | 566 | 55.7 | 368 | 37.2 | 146 | 37.7 | 272 | 43.9 | < 0.0001 |
 1 | 922 (28) | 249 | 24.5 | 310 | 31.3 | 95 | 24.5 | 163 | 26.3 |  |
 2 | 480 (15) | 120 | 11.8 | 156 | 15.8 | 70 | 18.1 | 94 | 15.2 |  |
  ≥ 3 | 375 (11) | 72 | 7.1 | 139 | 14.1 | 68 | 17.6 | 75 | 12.1 |  |
Endocrine | ||||||||||
 None | 1248 (40) | 48 | 5.1 | 126 | 14.2 | 357 | 97.5 | 584 | 97.2 | < 0.0001 |
 Tamoxifen | 1456 (47) | 687 | 72.9 | 591 | 66.7 | 7 | 1.9 | 15 | 2.5 |  |
 Aromatase Inhibitor | 395 (13) | 207 | 22.0 | 169 | 19.1 | 2 | 0.6 | 2 | 0.3 |  |
Chemotherapy | ||||||||||
 No | 799 (24) | 371 | 37.3 | 177 | 18.3 | 62 | 16.4 | 95 | 15.5 | < 0.0001 |
 Yes | 2483 (76) | 625 | 62.7 | 789 | 81.7 | 317 | 83.6 | 519 | 84.5 |  |
Surgery | ||||||||||
 No | 389 (12) | 80 | 10.2 | 106 | 15.8 | 53 | 19.4 | 87 | 16.3 | < 0.0001 |
 Yes | 2841 (88) | 913 | 89.8 | 833 | 84.2 | 312 | 80.6 | 519 | 83.7 |  |
Radiotherapy | ||||||||||
 No | 800 (26) | 261 | 27.7 | 218 | 24.6 | 79 | 23.9 | 149 | 26.4 | 0.01 |
 Yes | 2235 (74) | 683 | 72.3 | 669 | 75.4 | 252 | 76.1 | 416 | 73.6 |  |