Table 1 Association of HER2-low status with demographic and clinicopathological characteristics

Anatomic stage

0.308

   I/IIA

393 (17.4%)

565 (18.5%)

   IIB/III

1861 (82.6%)

2485 (81.5%)

T-stage

0.926

   T0/T1/Tis/TX

424 (18.8%)

561 (18.4%)

   T2

1264 (56.1%)

1717 (56.3%)

   T3/T4

566 (25.1%)

772 (25.3%)

N-stage

0.318

   N0

276 (12.2%)

422 (13.8%)

   N1

1109 (49.2%)

1498 (49.1%)

   N2

554 (24.6%)

731 (24.0%)

   N3

315 (14.0%)

398 (13.0%)

   Missing

0

1 (0.0%)

Histological grade

0. 890

   Grade 1

234 (10.4%)

331 (10.9%)

   Grade 2

1292 (57.3%)

1721 (56.4%)

   Grade 3

627 (27.8%)

854 (28.0%)

   Grade X/Missing

101 (4.5%)

144 (4.7%)

Age at randomization (years)

0.785

   Mean (SD)

53.1 (10.8)

53.0 (11.1)

   Min—Max

26.0 to 90.0

22.0 to 86.0

Menopausal status at randomization

0.660

   Postmenopausal

1209 (53.6%)

1635 (53.6%)

   Pre-/Perimenopausal

1032 (45.8%)

1391 (45.6%)

   Male/Missing

13 (0.6%)

24 (0.8%)

Baseline ECOG-PS

0.161

   0

1917 (85.0%)

2536 (83.1%)

   1/unknown

335 (14.9%)

512 (16.8%)

   Missing

2 (0.1%)

2 (0.1%)

BMI at randomization

0.047

   N

2222

3025

   Mean (SD)

27.7 (6.1)

27.9 (6.1)

   Min—Max

15.6 to 65.6

15.8 to 56.4

ER positive cells (%)

0.023

   N

1987

2726

   Mean (SD)

87.9 (17.3)

88.9 (17.0)

   Min—Max

0.0 to 100.0

0.0 to 100.0

PR positive cells (%)

0.094

   N

2007

2766

   Mean (SD)

59.7 (37.6)

58.3 (37.1)

   Min—Max

0.0 to 100.0

0.0 to 100.0

Primary surgery type

0.188

   Breast-conserving surgery

892 (39.6%)

1138 (37.3%)

   Mastectomy

1359 (60.3%)

1905 (62.5%)

   Both

3 (0.1%)

7 (0.2%)

Prior radiation

0.552

   No

241 (10.7%)

342 (11.2%)

   Yes

2012 (89.3%)

2708 (88.8%)

   Missing

1 (0.0%)

0

Prior chemotherapy

0.063

   No

422 (18.7%)

511 (16.8%)

   Yes

1832 (81.3%)

2539 (83.2%)