Relationship Between Levels Of Her-2 Amplification And Pathologic Complete Response To Trastuzumab-Based Neoadjuvant Treatment.

e11605 Background: Fluorescence in situ hybridization (FISH) is used to determine human epidermal growth factor receptor-2 (HER-2) status and patients (pts) eligibility for trastuzumab therapy. Using FISH as primary test, we analyzed the relationship between pathologic complete response (pCR) to trastuzumab-based neoadjuvant therapy and levels of HER-2 amplification in stage II-IIIa breast cancer. Methods: We retrospectively reviewed the data of 68 HER-2 positive breast cancer pts treated from January 2009 to June 2014 with trastuzumab based neoadjuvant therapy. Biopsies or cytological samples were analyzed by dual-color FISH using a HER-2 gene–specific probe and a centromeric probe for chromosome 17 (PathVysion HER-2 DNA Probe kit, Vysis-Abbott) to determine HER-2 amplification. Tumors were classified by FISH as follow: low amplification (LA) [Gene Copy Number (GCN) 10) or uncountable due to clusters of ...