Table 1.
Clinicopathological features by HER2 and hormone receptor status
| Total (%) | Hormone receptor-positive (%) | Hormone receptor-negative (%) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| HER2-zero (n = 16,020) |
HER2low (n = 12,260) |
P | HER2-zero (n = 12,712) |
HER2-low (n = 10,791) |
P | HER2-zero (n = 3272) |
HER2-low (n = 1362) |
P | |
| Age at diagnosis, years | |||||||||
| Below 35 | 787 (4.9) | 541 (4.4) | 0.071 | 528 (4.2) | 455 (4.2) | 0.014 | 256 (7.8) | 77 (5.7) | < 0.001 |
| 35–49 | 7448 (46.5) | 5798 (47.3) | 6131 (48.2) | 5244 (48.6) | 1291 (39.5) | 466 (34.2) | |||
| 50–64 | 5639 (35.2) | 4357 (35.5) | 4319 (34.0) | 3768 (34.9) | 1315 (40.2) | 581 (42.7) | |||
| 65 and over | 2146 (13.4) | 1564 (12.8) | 1734 (13.6) | 1324 (12.3) | 410 (12.5) | 238 (17.5) | |||
| Ethnicity | |||||||||
| Chinese | 5203 (32.5) | 4674 (38.1) | < 0.001 | 4344 (34.2) | 4183 (38.8) | < 0.001 | 853 (26.1) | 483 (35.5) | < 0.001 |
| Malay | 374 (2.3) | 220 (1.8) | 301 (2.4) | 194 (1.8) | 73 (2.2) | 26 (1.9) | |||
| Indian | 253 (1.6) | 149 (1.2) | 191 (1.5) | 123 (1.1) | 62 (1.9) | 26 (1.9) | |||
| Korean | 6873 (42.9) | 5363 (43.7) | 5245 (41.3) | 4739 (43.9) | 1622 (49.6) | 613 (45.0) | |||
| Japanese | 3182 (19.9) | 1782 (14.5) | 2516 (19.8) | 1488 (13.8) | 642 (19.6) | 206 (15.1) | |||
| Others | 135 (0.8) | 72 (0.6) | 115 (0.9) | 64 (0.6) | 20 (0.6) | 8 (0.6) | |||
| Year of diagnosis | |||||||||
| 2000–2005 | 2171 (13.6) | 906 (7.4) | < 0.001 | 1697 (13.4) | 714 (6.6) | < 0.001 | 466 (14.2) | 172 (12.6) | 0.002 |
| 2006–2010 | 6501 (40.6) | 3835 (31.3) | 5069 (39.9) | 3286 (30.5) | 1421 (43.4) | 538 (39.5) | |||
| 2011–2015 | 7348 (45.9) | 7519 (61.3) | 5946 (46.8) | 6791 (62.9) | 1385 (42.3) | 652 (47.9) | |||
| Histology | |||||||||
| IDCa | 14,090 (88.0) | 11,043 (90.1) | < 0.001 | 11,019 (86.7) | 9665 (89.6) | < 0.001 | 3040 (92.9) | 1277 (93.8) | 0.323 |
| ILCa | 895 (5.6) | 688 (5.6) | 821 (6.5) | 654 (6.1) | 72 (2.2) | 32 (2.4) | |||
| Others | 1035 (6.5) | 529 (4.3) | 872 (6.9) | 472 (4.4) | 160 (4.9) | 53 (3.9) | |||
| T-stage | |||||||||
| T1 | 8828 (55.1) | 6815 (55.6) | 0.003 | 7413 (58.3) | 6112 (56.6) | 0.002 | 1392 (42.5) | 635 (46.6) | 0.100 |
| T2 | 6011 (37.5) | 4629 (37.8) | 4472 (35.2) | 4008 (37.1) | 1528 (46.7) | 594 (43.6) | |||
| T3 | 719 (4.5) | 557 (4.5) | 528 (4.2) | 478 (4.4) | 189 (5.8) | 75 (5.5) | |||
| T4 | 309 (1.9) | 167 (1.4) | 209 (1.6) | 131 (1.2) | 100 (3.1) | 30 (2.2) | |||
| Othersb | 103 (0.6) | 58 (0.5) | 46 (0.4) | 30 (0.3) | 57 (1.7) | 27 (2.0) | |||
| Unknown | 50 (0.3) | 34 (0.3) | 44 (0.4) | 32 (0.3) | 6 (0.2) | 1 (0.1) | |||
| N-stage | |||||||||
| N0 | 10,412 (65.0) | 7679 (62.6) | 0.001 | 8199 (64.5) | 6754 (62.6) | 0.042 | 2191 (67.0) | 855 (62.8) | 0.005 |
| N1 | 3865 (24.1) | 3101 (25.3) | 3118 (24.5) | 2760 (25.6) | 735 (22.5) | 319 (23.4) | |||
| N2 | 1081 (6.8) | 920 (7.5) | 887 (7.0) | 810 (7.5) | 194 (5.9) | 102 (7.5) | |||
| N3 | 647 (4.0) | 543 (4.4) | 494 (3.9) | 453 (4.2) | 151 (4.6) | 83 (6.1) | |||
| NX | 15 (0.1) | 17 (0.1) | 14 (0.1) | 14 (0.1) | 1 (0.0) | 3 (0.2) | |||
| Overall stage | |||||||||
| Stage 1 | 6782 (42.3) | 5217 (42.6) | 0.159 | 5732 (45.1) | 4712 (43.7) | 0.050 | 1034 (31.6) | 452 (33.2) | 0.033 |
| Stage 2 | 6881 (43.0) | 5154 (42.0) | 5206 (41.0) | 4485 (41.6) | 1657 (50.6) | 636 (46.7) | |||
| Stage 3 | 2357 (14.7) | 1889 (15.4) | 1774 (14.0) | 1594 (14.8) | 581 (17.8) | 274 (20.1) | |||
| ER receptor status | |||||||||
| Positive | 12,338 (77.0) | 10,578 (86.3) | < .0001 | 12,338 (97.1) | 10,578 (98.0) | < 0.001 | 0 (–) | 0 (–) | - |
| Negative | 3643 (22.7) | 1574 (12.8) | 371 (2.9) | 210 (2.0) | 3272 (100) | 1362 (100) | |||
| Unknownc | 39 (0.2) | 108 (0.9) | 3 (0.0) | 3 (0.0) | 0 (–) | 0 (–) | |||
| PR receptor status | |||||||||
| Positive | 10,832 (67.6) | 9296 (75.8) | < 0.001 | 10,832 (85.2) | 9296 (86.2) | 0.050 | 0 (–) | 0 (–) | – |
| Negative | 5136 (32.1) | 2853 (23.3) | 1864 (14.7) | 1488 (13.8) | 3272 (100) | 1362 (100) | |||
| Unknownb | 52 (0.3) | 111 (0.9) | 16 (0.1) | 7 (0.1) | 0 (–) | 0 (–) | |||
| Tumour grade | |||||||||
| Grade 1 | 3586 (22.4) | 2745 (22.4) | < 0.001 | 3471 (27.3) | 2657 (24.6) | < 0.001 | 104 (3.2) | 47 (3.5) | 0.028 |
| Grade 2 | 6544 (40.9) | 5601 (45.7) | 5882 (46.3) | 5277 (48.9) | 648 (19.8) | 291 (21.4) | |||
| Grade 3 | 4879 (30.5) | 3219 (26.3) | 2552 (20.1) | 2296 (21.3) | 2321 (70.9) | 914 (67.1) | |||
| Unknown | 1011 (6.3) | 695 (5.7) | 807 (6.4) | 561 (5.2) | 199 (6.1) | 110 (8.1) | |||
| Received radiotherapyd | |||||||||
| Applicable—no | 2487 (15.5) | 1957 (16.0) | < 0.001 | 2045 (16.1) | 1742 (16.1) | < 0.001 | 432 (13.2) | 189 (13.9) | 0.267 |
| Applicable—yes | 6302 (39.3) | 4114 (33.6) | 5015 (39.5) | 3583 (33.2) | 1272 (38.9) | 495 (36.3) | |||
| Not applicable | 7231 (45.1) | 6189 (50.5) | 5652 (44.5) | 5466 (50.7) | 1568 (47.9) | 678 (49.8) | |||
| Received endocrine therapyc,d | |||||||||
| Applicable—no | 1214 (7.6) | 978 (8.0) | < 0.001 | 1214 (9.6) | 978 (9.1) | 0.208 | 0 (–) | 0 (–) | – |
| Applicable—yes | 11,498 (71.8) | 9813 (80.0) | 11,498 (90.5) | 9813 (90.9) | 0 (–) | 0 (–) | |||
| Not applicable | 3272 (20.4) | 1362 (11.1) | 0 (–) | 0 (–) | 3272 (100) | 1362 (100) | |||
| Unknown | 36 (0.2) | 107 (0.9) | 0 (–) | 0 (–) | 0 (–) | 0 (–) | |||
| Received chemotherapyc,d | |||||||||
| Applicable—no | 2065 (12.9) | 1624 (13.3) | 0.677 | 1760 (13.9) | 1446 (13.4) | 0.003 | 296 (9.1) | 154 (11.3) | 0.048 |
| Applicable—yes | 7507 (46.9) | 5744 (46.9) | 5455 (42.9) | 4879 (45.2) | 2041 (62.4) | 836 (61.4) | |||
| Not applicable | 5695 (35.6) | 4297 (35.1) | 4925 (38.7) | 3959 (36.7) | 756 (23.1) | 287 (21.1) | |||
| Unknown | 753 (4.7) | 595 (4.9) | 572 (4.5) | 507 (4.7) | 179 (5.5) | 85 (6.2) | |||
a IDC invasive ductal carcinoma, ILC invasive lobular carcinoma
b TX Tis and T0
c Included 4 patients with equivocal test result; combined with an unknown category for analysis due to small sample size
d Patients were deemed applicable for radiotherapy if the N-stage was N1–3, T-stage was T3–4 or they had undergone breast-conserving surgery. They were deemed applicable for endocrine therapy if the tumour was ER- or PR-positive. They were deemed applicable for chemotherapy if the N-stage was N1–3, T-stage was T2–4 or tumour size ≥ 10 mm and had any of following risk factors: Grade 3 tumour, ER-negative or HER2-positive. These criteria were adapted from our previous study [27]