Table 2 Patients’ characteristics according to the risk cohort.

From: Prognostic impact of HER2-low positivity in patients with HR-positive, HER2-negative, node-positive early breast cancer

Category

Cohort 1

Cohort 2

Cohort 3

HER2-zero

(n = 124)

HER2-low

(n = 227)

p-value

HER2-zero

(n = 34)

HER2-low

(n = 73)

p-value

HER2-zero

(n = 70)

HER2-low

(n = 119)

p-value

n

%

n

%

n

%

n

%

n

%

n

%

Age, years

 < 65

92

(74.2)

173

(76.2)

0.674

26

(76.5)

63

(86.3)

0.206

57

(81.4)

89

(74.8)

0.293

 ≥ 65

32

(25.8)

54

(23.8)

 

8

(23.5)

10

(13.7)

 

13

(18.6)

30

(25.2)

 

Sex

 Female

123

(99.2)

225

(99.1)

0.942

34

(100)

71

(97.3)

0.330

70

(100)

119

(100)

N. A

 Male

1

(0.8)

2

(0.9)

 

0

(0)

2

(2.7)

 

0

(0)

0

(0)

 

Menopausal status

 Pre

54

(43.6)

111

(48.9)

0.337

18

(52.9)

41

(56.2)

0.755

31

(44.3)

66

(55.5)

0.138

 Post

70

(56.5)

116

(51.1)

 

16

(47.1)

32

(43.8)

 

39

(55.7)

53

(44.5)

 

ER status

 Negative

2

(1.6)

3

(1.3)

0.826

0

(0)

0

(0)

N. A

0

(0)

0

(0)

N. A

 Positive

122

(98.4)

224

(98.7)

 

34

(100)

73

(100)

 

70

(100)

119

(100)

 

PR status

 Negative

17

(13.7)

25

(11.0)

0.457

2

(5.9)

6

(8.2)

0.669

3

(4.3)

4

(3.4)

0.745

 Positive

107

(86.3)

202

(89.0)

 

32

(94.1)

67

(91.8)

 

67

(95.7)

115

(96.6)

 

HER2 status

 IHC0

124

(100)

0

(0)

< 0.001

34

(100)

0

(0)

< 0.001

70

(100)

0

(0)

< 0.001

 IHC1+

0

(0)

151

(66.5)

 

0

(0)

53

(72.6)

 

0

(0)

88

(74.0)

 

 IHC2+/FISH−

0

(0)

76

(33.5)

 

0

(0)

20

(27.4)

 

0

(0)

31

(26.1)

 

Histological type

 IDC

95

(76.6)

186

(81.9)

0.204

27

(79.4)

66

(90.4)

0.110

58

(82.9)

102

(85.7)

0.721

 ILC

22

(17.7)

23

(10.1)

 

4

(11.8)

1

(1.4)

 

10

(14.3)

12

(10.1)

 

 IDC + ILC

2

(1.6)

4

(1.8)

 

1

(2.9)

1

(1.4)

 

0

(0)

1

(0.8)

 

 Others

5

(4.0)

14

(6.2)

 

2

(5.9)

5

(6.9)

 

2

(2.9)

4

(3.4)

 

HG

 1

9

(7.3)

19

(8.4)

0.933

3

(8.8)

8

(11.0)

0.735

20

(28.6)

53

(44.5)

0.029

 2

46

(37.1)

84

(37.0)

 

31

(91.2)

65

(89.0)

 

50

(71.4)

66

(55.5)

 

 3

69

(55.7)

124

(54.6)

 

0

(0)

0

(0)

 

0

(0)

0

(0)

 

Tumor size, cm

 < 2

27

(21.8)

59

(26.0)

0.190

12

(35.3)

37

(50.7)

0.137

39

(55.7)

67

(56.3)

0.937

 2–5

54

(43.6)

110

(48.5)

 

22

(64.7)

36

(49.3)

 

31

(44.3)

52

(43.7)

 

 ≥ 5

43

(34.7)

58

(25.6)

 

0

(0)

0

(0)

 

0

(0)

0

(0)

 

Number of positive lymph nodes

 1–3

53

(42.7)

114

(50.2)

0.180

34

(100)

73

(100)

N. A

70

(100)

119

(100)

N. A

 ≥ 4

71

(57.3)

113

(49.8)

 

0

(0)

0

(0)

 

0

(0)

0

(0)

 

Ki-67 index, %

 < 20

38

(30.7)

68

(30.0)

0.893

0

(0)

0

(0)

N. A

70

(100)

119

(100)

N. A

 ≥ 20

86

(69.4)

159

(70.0)

 

34

(100)

73

(100)

 

0

(0)

0

(0)

 

Breast surgery

 BCS

38

(30.7)

56

(24.7)

0.227

17

(50.0)

25

(34.3)

0.120

29

(41.4)

54

(45.4)

0.597

 TM

86

(69.4)

171

(75.3)

 

17

(50.0)

48

(65.8)

 

41

(58.6)

65

(54.6)

 

Axillary surgery

 SLNB only

6

(4.8)

10

(4.4)

0.852

2

(5.9)

8

(11.0)

0.401

9

(12.9)

30

(25.2)

0.043

 ALND

118

(95.2)

217

(95.6)

 

32

(94.1)

65

(89.0)

 

61

(87.1)

89

(74.8)

 

RT

 Yes

110

(88.7)

168

(74.0)

0.001

17

(50.0)

32

(43.8)

0.551

32

(45.7)

50

(42.0)

0.620

 No

14

(11.3)

59

(26.0)

 

17

(50.0)

41

(56.2)

 

38

(54.3)

69

(58.0)

 

CT

 Neoadjuvant

20

(16.1)

52

(22.9)

0.310

3

(8.8)

7

(9.6)

0.939

1

(1.4)

1

(0.8)

0.677

 Adjuvant

86

(69.4)

147

(64.8)

 

23

(67.7)

51

(69.9)

 

31

(44.3)

46

(38.7)

 

 No

18

(14.5)

28

(12.3)

 

8

(23.5)

15

(20.6)

 

38

(54.3)

72

(60.5)

 

ET

 Yes

115

(92.7)

223

(98.2)

0.009

33

(97.1)

71

(97.3)

0.953

66

(94.3)

114

(95.8)

0.637

 No

9

(7.3)

4

(1.8)

 

1

(2.9)

2

(2.7)

 

4

(5.7)

5

(4.2)

 
  1. ER estrogen receptor, PR progesterone receptor, HER2 human epidermal growth factor receptor 2, IDC invasive ductal carcinoma, ILC invasive lobular carcinoma, HG histological grade, BCS breast-conserving surgery, TM total mastectomy, SLNB sentinel lymph node biopsy, ALND axillary lymph node dissection, RT radiotherapy, CT chemotherapy, ET endocrine therapy, FISH fluorescence in situ hybridization.
  2. HER2-zero group: Patients with immunohistochemistry (IHC) 0 score.
  3. HER2-low group: Patients with IHC1+ or IHC2+/FISH− scores.
  4. Cohort 1: Patients with ≥ 4 positive axillary lymph nodes (ALNs), or 1–3 positive ALNs, and either histological grade (HG) 3 or tumor size ≥ 5 cm.
  5. Cohort 2: Patients with 1–3 positive ALNs, HG < 3, tumor size < 5 cm, and high Ki-67 index (≥ 20%).
  6. Cohort 3: Patients with 1–3 positive ALNs, HG < 3, tumor size < 5 cm, and low Ki-67 index (< 20%).
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