(Phospho)proteomics profiling of pre-treatment HER2+ BC biopsies

In this study, we perform (phospho)proteomics analysis of 45 pre-treatment HER2+ needle biopsies of early-stage invasive breast cancer to identify molecular signatures predictive of treatment response to Trastuzumab, Pertuzumab and chemotherapy. All patient biopsies included in this study were classified as HER2+ with a minimum tumour grade of two and tumour cell density of 60% or higher. After needle biopsies were taken, patients completed multiple drug treatment cycles according to the regime of the TRAIN2 study. Finally, treatment response was determined at surgery. The systemic treatment response was categorised as pathological complete response (pCR = ypT0/isypN0) (n=26), near pCR (npCR) (n=8), or No pCR (n=11).