Table 1.
Clinicopathological characteristics of patients with HER2-low breast cancer according to hormone receptor status
| Variables | All patients (N = 30,491) | P value | HR-positive (N = 23,539)a | P value | HR-negative (N = 6,934) | P value | |||
|---|---|---|---|---|---|---|---|---|---|
| HER2_0 | HER2_L | HER2_0 | HER2_L | HER2_0 | HER2_L | ||||
| Age, median (range), yb | 48 (20–94) | 49 (21–92) | .127 | 48 (20–94) | 49 (23–90) | .267 | 48 (20–91) | 50 (21–91) | .001 |
| Age, No, (%), yb | .267 | .462 | .410 | ||||||
| < 40 | 2,997 (14.2) | 1,311 (13.8) | 1,934 (12.4) | 1,016 (12.9) | 1,062 (19.9) | 295 (18.5) | |||
| ≥ 40 | 17,985 (85.8) | 81,76 (86.2) | 13,682 (87.6) | 68,77 (87.1) | 4,268 (80.1) | 1,297 (81.5) | |||
| Sex, No. (%) | .021 | .084 | .547 | ||||||
| Female | 20,909 (99.6) | 9,454 (99.4) | 15,557 (99.5) | 7,860 (99.4) | 5,336 (99.9) | 1,592 (99.9) | |||
| Male | 76 (0.4) | 52 (0.6) | 72 (0.5) | 50 (0.6) | 4 (0.1) | 2 (0.1) | |||
| Menopausal status, No. (%)b | .001 | .001 | .505 | ||||||
| Premenopause | 7,474 (68.6) | 4,373 (72.5) | 5,541 (70.6) | 3,628 (74.3) | 1,928 (63.3) | 739 (64.4) | |||
| Postmenopause | 3,423 (31.4) | 1,660 (27.5) | 2,305 (29.4) | 1,252 (25.7) | 1,117 (36.7) | 408 (35.6) | |||
| BMI, No. (%), kg/m2 | .001 | .001 | .015 | ||||||
| < 25 | 16,176 (77.1) | 7,087 (74.6) | 12,104 (77.4) | 5,921 (74.8) | 4,059 (76.0) | 1,164 (73.0) | |||
| ≥ 25 | 4,809 (22.9) | 2,419 (25.4) | 3,525 (22.6) | 1,989 (25.2) | 1,281 (24.0) | 430 (27.0) | |||
| Presence of FHx, No. (%)b | 1,394 (8.5) | 739 (9.5) | .010 | 1,003 (8.2) | 612 (9.4) | .005 | 391 (9.4) | 127 (10.0) | .500 |
| Tumor location, No. (%)b | .447 | .220 | .546 | ||||||
| Right | 9,752 (50.0) | 4,066 (49.9) | 7,393 (50.7) | 3,403 (50.0) | 2,354 (48.1) | 670 (49.8) | |||
| Left | 9,703 (49.8) | 4,078 (50.0) | 7,165 (49.1) | 3,395 (49.9) | 2,533 (51.7) | 674 (50.1) | |||
| Both | 43 (0.2) | 9 (0.1) | 26 (0.3) | 7 (0.1) | 8 (0.2) | 2 (0.1) | |||
| Pathological stage, No. (%) | .121 | .334 | .147 | ||||||
| Stage I | 9,571 (45.6) | 4,454 (46.9) | 7,539 (48.3) | 3,810 (48.2) | 2,024 (37.9) | 642 (40.3) | |||
| Stage II | 8,860 (42.2) | 3,935 (41.4) | 6,180 (39.5) | 3,181 (40.2) | 2,673 (50.1) | 754 (47.3) | |||
| Stage III | 2,554 (12.2) | 1,117 (11.7) | 1,910 (12.2) | 919 (11.6) | 643 (12.0) | 198 (12.4) | |||
| pT stage, No. (%)c | .001 | .041 | .050 | ||||||
| T1 | 12,522 (59.8) | 5,801 (61.1) | 9,967 (63.9) | 5,001 (63.3) | 2,546 (47.8) | 798 (50.2) | |||
| T2 | 7,594 (36.2) | 3,365 (35.4) | 5,078 (32.5) | 2,631 (33.3) | 2,510 (47.1) | 734 (46.2) | |||
| T3 | 688 (3.3) | 291 (3.1) | 467 (3.0) | 240 (3.0) | 220 (4.2) | 51 (3.2) | |||
| T4 | 146 (0.7) | 35 (0.4) | 97 (0.6) | 28 (0.4) | 49 (0.9) | 7 (0.4) | |||
| pN stage, No. (%) | .104 | .213 | .623 | ||||||
| N0 | 13,702 (65.3) | 6,118 (64.4) | 10,047 (64.3) | 5,048 (63.8) | 3,643 (68.2) | 1,068 (67.0) | |||
| N1 | 4,978 (23.7) | 2,376 (25.0) | 3,856 (24.7) | 2,034 (25.7) | 1,119 (21.0) | 342 (21.5) | |||
| N2 | 1,430 (6.8) | 636 (6.7) | 1,094 (7.0) | 536 (6.8) | 335 (6.3) | 100 (6.3) | |||
| N3 | 875 (4.2) | 376 (3.9) | 632 (4.0) | 292 (3.7) | 243 (4.5) | 84 (5.2) | |||
| LNR, mean ± SD | 0.085 ± 0.18 | 0.092 ± 0.20 | .005 | 0.088 ± 0.18 | 0.092 ± 0.19 | .104 | 0.077 ± 0.17 | 0.090 ± 0.20 | .018 |
| Histological type, No. (%)d | .007 | .333 | .059 | ||||||
| Invasive ductal | 19,683 (96.4) | 8,942 (95.8) | 14,552 (95.5) | 7,406 (95.3) | 5,122 (99.1) | 1,534 (98.6) | |||
| Invasive lobular | 725 (3.6) | 391 (4.2) | 680 (4.5) | 369 (4.7) | 45 (0.9) | 22 (1.4) | |||
| Histological grade, No. (%) | .001 | .001 | .205 | ||||||
| G1 | 4,232 (20.2) | 1,831 (19.3) | 4,029 (25.8) | 1,770 (22.4) | 200 (3.7) | 61 (3.8) | |||
| G2 | 8,430 (40.2) | 4,437 (46.7) | 7,341 (47.0) | 4,081 (51.6) | 1,087 (20.4) | 355 (22.3) | |||
| G3 | 6,534 (31.1) | 2,500 (26.3) | 2,940 (18.8) | 1,473 (18.6) | 3,591 (67.2) | 1,027 (64.4) | |||
| Unknown | 1,789 (8.5) | 738 (7.7) | 1,319 (8.4) | 586 (7.4) | 462 (8.7) | 151 (9.5) | |||
| Nuclear grade, No. (%) | .001 | .001 | .783 | ||||||
| G1 | 2,483 (11.8) | 849 (8.9) | 2,342 (15.0) | 806 (10.3) | 141 (2.6) | 43 (2.7) | |||
| G2 | 9,217 (44.0) | 4,650 (48.9) | 8,205 (52.5) | 4,322 (54.6) | 1,007 (18.9) | 327 (20.5) | |||
| G3 | 6,380 (30.4) | 2,523 (26.6) | 2,968 (19.0) | 1,568 (19.8) | 3,410 (63.9) | 954 (59.9) | |||
| Unknown | 2,905 (13.8) | 1,484 (15.6) | 2,114 (13.5) | 1,214 (15.3) | 782 (14.6) | 270 (16.9) | |||
| Presence of LI, No. (%)b | 5,231 (24.9) | 2,712 (28.5) | .001 | 3,913 (25.0) | 2,284 (14.6) | .001 | 1,316 (24.6) | 428 (26.9) | .001 |
| Presence of VI, No. (%)b | 2,737 (13.0) | 1,171 (12.3) | .148 | 2,048 (13.1) | 960 (12.1) | .338 | 689 (12.9) | 211 (13.2) | .202 |
| Ki-67, No. (%)b | |||||||||
| < 14% | 4,962 (48.2) | 3,035 (58.7) | .001 | 4,415 (57.6) | 2,793 (65.2) | .001 | 539 (20.7) | 242 (27.4) | .001 |
| ≥ 14% | 5,328 (51.8) | 2,134 (41.3) | 3,256 (42.4) | 1,491 (34.8) | 2,069 (79.3) | 642 (72.6) | |||
| < 20% | 5,752 (55.9) | 3,390 (65.6) | .001 | 5,115 (66.7) | 3,095 (72.2) | .001 | 629 (24.1) | 295 (33.4) | .001 |
| ≥ 20% | 4,538 (44.1) | 1,779 (34.4) | 2,556 (33.3) | 1,189 (27.8) | 1,979 (75.9) | 589 (66.6) | |||
| Breast surgery, No. (%)b | .001 | .004 | .044 | ||||||
| BCS | 12,972 (62.5) | 5,656 (60.3) | 9,603 (62.1) | 4,698 (60.2) | 3,363 (63.6) | 958 (60.8) | |||
| TM | 7,798 (37.5) | 3,731 (39.7) | 5,863 (37.9) | 3,111 (39.8) | 1,927 (36.4) | 618 (39.2) | |||
| Axillary surgery, No. (%) | .001 | .001 | .545 | ||||||
| SLNB | 6,111 (29.1) | 3,236 (34.0) | 4,616 (29.6) | 2,765 (35.0) | 1,494 (28.0) | 470 (29.5) | |||
| SLNB & ALND | 4,177 (19.9) | 2,366 (25.0) | 3,196 (20.4) | 2,023 (25.6) | 980 (18.3) | 343 (21.5) | |||
| ALND | 9,353 (44.6) | 3,465 (36.4) | 6,790 (43.4) | 2,751 (34.8) | 2,559 (48.0) | 714 (44.8) | |||
| No surgery | 1,344 (6.4) | 439 (4.6) | 1,027 (6.6) | 371 (4.7) | 307 (5.7) | 67 (4.2) | |||
| Adjuvant RT, No. (%)b | .922 | .747 | .658 | ||||||
| Yes | 13,220 (69.1) | 5,882 (69.2) | 9,773 (68.5) | 4,856 (68.7) | 3,444 (71.0) | 1,026 (71.6) | |||
| No | 5,907 (30.9) | 2,621 (30.8) | 4,497 (31.5) | 2,212 (31.3) | 1,407 (29.0) | 407 (28.4) | |||
| Adjuvant CT, No. (%)b | .002 | .347 | .141 | ||||||
| Yes | 13,979 (71.3) | 6,099 (69.4) | 9,466 (64.9) | 4,774 (65.5) | 4,509 (89.9) | 1,325 (88.6) | |||
| No | 5,633 (28.7) | 2,685 (30.6) | 5,124 (35.1) | 2,512 (34.5) | 507 (10.1) | 171 (11.4) | |||
HR hormone receptor; HER2 human epidermal growth factor receptor 2; HER2_0 HER2-IHC 0 breast cancer; HER2_L HER2-low breast cancer; BMI body mass index; FHx family history; pT stage pathological T stage; pN stage pathological N stage; LNR lymph node ratio; SD standard deviation; LI lymphatic invasion; VI vascular invasion; BCS breast conserving surgery; TM total mastectomy; SLNB sentinel lymph node biopsy; ALND axillary lymph node dissection; RT radiotherapy; CT chemotherapy
aHormone receptor status was available for a total of 30,473 patients: 23,539 in the hormone receptor-positive group, and 6934 in the hormone receptor-negative group
bThese variables have missing data
cThe cases of T0 are not described here
dThe cases of other histology are not described here