Abstract
Abstract Background: The aim of this study was to compare the HER2 gene amplification index (AI) of luminal B and HER-2 enriched breast cancers using fluorescence in situ hybridization (FISH). Methods: Out of 753 patients with breast cancer who were tested HER2 status by FISH between Jan 2004 to Dec 2009, 224 HER2 amplified patients were available for this study. HER2-amplified breast cancers constitute a heterogenous group that may be subdivided according to their ER status: HER2 amplified ER-positive breast carcinomas that fall into the luminal B group; and HER2 amplified ER-negative cancers which form a distinct molecular subtype, known as the HER2 enriched group according to hormone status by immunohistochemistry and HER2 amplification confirmed as HER2/CEP17 ratio by FISH. A difference of HER2 AI was analyzed between luminal B and HER-2 enriched group. Clinicopathologic parameters were analyzed. Results: Among the HER2 amplified patients, the proportion of luminal B and HER2 breast cancer was 53.5% (N=120) and 46.5% (N=104), respectively. Early breast cancer patients were 84.8% (N=190) and metastatic breast cancer patients were 15.2% (N=34). HER-2 AI of luminal B group and HER2 enriched group were 4.99 and 5.84 respectively, which values showed the quantitative difference statistically significant (p=0.003). However, increasing value of HER2 AI was not associated with a better overall survival or progression free survival. In luminal B group, a significant difference of HER2 AI between ER/PR +/+ subgroup and ER/PR +/- subgroup existed which were 4.02 and 5.32, respectively (p=0004). Conclusions: The HER2 AI of HER2 enriched group was higher than that of luminal B group statistically significant. It was not clear whether the extent of HER-2 amplification relates to the survival benefit of treatment in HER-2 positive breast cancer. Further research to understand how the level of HER2 amplification is related to prognosis is warranted in order to understand the breast cancer biology associated with the intrinsic subtypes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3897. doi:10.1158/1538-7445.AM2011-3897
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