In a recent study, HER2-overexpressing early breast cancer patients who had received neoadjuvant trastuzumab were included to evaluate whether pathologic complete response (pCR) to neoadjuvant trastuzumab is dependent on the level of HER2 amplification. Absolute HER2 and chromosome 17 centromere (CEP17) were measured by in situ hybridization analysis, and associations were examined between HER2/CEP17 ratio and tumor pCR status (commonly defined by ypT0 ypN0, ypT0/is ypN0, and ypT0/is).
This study indicates that a subgroup of patients (stage yPT0 and pN0) achieved a greater complete response if the ratio HER2 / CEP17 > 6, (69%) vs ratio HER2 / CEP17≤6 (30.4%); As well as in the case of patients with ypt0/is ypN0 (75.9% vs39.1%) and ypTis (82.8% vs.38.3%), as long as the tumors were hormone receptor (HR)–positive tumors .
From this study it was concluded that an HER2/CEP17 ratio of >6 in the pretherapeutic tumor biopsy is associated with a significantly higher pCR rate, particularly in HER2/HR co-positive tumors, and can be used as a biomarker to predict response before neoadjuvant trastuzumab is initiated.
https://www.ncbi.nlm.nih.gov/pubmed/28143867
