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Table 2 Baseline characteristics and association between dichotomized serum HER2 ECD level and clinicopathologic variables

From: Preoperative serum HER2 extracellular domain levels in primary invasive breast cancer

Characteristics Total group Subgroup with normal serum HER2 ECD level (≤15.2 ng/ml) Subgroup with elevated serum HER2 ECD level (>15.2 ng/ml) P a
  n % n % n %  
Total patients 2,862 100% 2,736 100% 126 100%  
Serum HER2 ECD, ng/ml
 Mean ± SD 10.1 ± 9.4 9.3 ± 1.9 27.3 ± 40.4 <0.001b
 Median (range) 9.2 (3.3–427.8) 9.1 (3.3–15.2) 18.5 (15.3–427.8)  
Age at diagnosis, years        0.860b
 Mean ± SD 48.5 ± 9.9 48.5 ± 9.9 48.4 ± 10.3  
 Median (range) 48 (22–94) 48.0 (22–94) 49.0 (26–88)  
Age subgroup, years
  ≤ 34 172 6% 162 6% 10 8% 0.100
 35–49 1,510 53% 1,455 53% 55 44%  
  ≥ 50 1,180 41% 1,119 41% 61 48%  
Stage
 I/II 2,457 86% 2,376 87% 81 64% <0.001
 III 405 14% 360 13% 45 36%  
Tumor size, cm
  ≤ 2 1,676 59% 1,625 59% 51 40% <0.001
  > 2 1,186 41% 1,111 41% 75 60%  
Lymph node
 Negative 1,749 61% 1,694 62% 55 44% <0.001
 Positive 1,113 39% 1,042 38% 71 56%  
Histologic grade
 1/2 1,787 64% 1,734 65% 53 43% <0.001
 3 1,025 36% 954 35% 71 57%  
 Unknown 50   48   2   
Nuclear grade
 1/2 1,775 63% 1,730 64% 45 41% <0.001
 3 1,049 37% 984 36% 65 59%  
 Unknown 38   22   16   
LVI
 Negative 2,095 76% 2,007 76% 88 75% 0.830
 Positive 660 24% 631 24% 29 25%  
 Unknown 107   98   9   
Hormone-receptor status
 Negative 916 32% 831 30% 85 68% <0.001
 Positivec 1,940 68% 1,899 70% 41 32%  
 Unknown 6   6   0   
Tissue HER2 status
 Negative 2,168 76% 2,146 79% 22 17% <0.001
 Positived 692 24% 588 21% 104 83%  
 Unknown 2   2   0   
Definitive surgery        <0.001
 Conservation 1,781 62% 1,743 64% 38 30%  
 Mastectomy 1,081 38% 993 36% 88 70%  
Radiotherapy
 Yes 2,047 72% 1,973 72% 74 59% 0.001
 No 813 28% 761 28% 52 41%  
 Unknown 2   2   0   
Chemotherapy
 Yes 1,852 65% 1,746 64% 106 84% <0.001
 No 1,007 35% 987 36% 20 16%  
 Unknown 3   3   0   
Anti-HER2 therapy
 Yes 264 9% 211 8% 53 42% <0.001
 No 2,598 91% 2,525 92% 73 58%  
  1. aCalculated by chi-square test except where stated otherwise.
  2. bCalculated by t-test.
  3. cEstrogen- and/or progesterone-receptor positive.
  4. dGraded as 3+ on IHC or 2+ on fluorescence in situ hybridization in cases of IHC 2+.