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Table 3 Overlap of HER2 mRNA level, PI3K mutation status, and HER2 IHC staining pattern biomarker subgroups

From: Relationship between tumor biomarkers and efficacy in MARIANNE, a phase III study of trastuzumab emtansine ± pertuzumab versus trastuzumab plus taxane in HER2-positive advanced breast cancer

Biomarker subgroup Patients n (%a)
HER2 mRNA and PI3K status available (N = 951) HER2 mRNA level PI3K mutation status  
≤median (n = 484) Mutated 171 (35.3)
  Non-mutated 313 (64.7)
>median (n = 467) Mutated 86 (18.4)
  Non-mutated 381 (81.6)
HER2 mRNA and HER2 IHC expression available (N = 989) HER2 mRNA level HER2 IHC expression  
≤median (n = 495) Focal/heterogeneous 114 (23.0)
  Homogeneous 381 (77.0)
>median (n = 494) Focal/heterogeneous 19 (3.8)
  Homogeneous 475 (86.6)
PI3K mutation status and HER2 IHC expression available (N = 976) HER2 IHC expression PI3K mutation status  
Focal/heterogeneous (n = 136) Mutated 57 (41.9)
  Non-mutated 79 (58.1)
Homogeneous (n = 840) Mutated 202 (24.0)
  Non-mutated 638 (76.0)
  1. aPercentage based on number of patients with both biomarkers available and calculated within subgroups. HER2 mRNA missing n = 96; PI3K mutation status missing n = 109; IHC H score missing n = 10
  2. HER2 human epidermal growth factor receptor 2, IHC immunohistochemistry, PI3K phosphoinositide 3-kinase