Survival Analyses in Breast Cancer According to Over-expression and Amplification of HER2

Kim, Sin Sun; Park, Woo Chan; Lee, Dong Ho; Kim, Jeong Soo; Oh, Se Jeong; Song, Byung Joo; Jung, Sang Seol; Myung, Jeon Hye; Lee, Jae Hak

Abstract

PURPOSE
HER2 is a 185-kDa transmembrane protein, which shares a considerable homology with the epidermal growth factor receptor. The over-expression of HER2 has been reported to be associated with a poor clinical outcome in breast cancer. In clinical practice and research studies, immunohistochemistry (IHC) and fluorescence in-situ hybridization (FISH) have commonly been used for the detection of HER2. The aim of this study was to evaluate the prognostic significance of HER2 according to the results of IHC and FISH for HER2. METHODS: IHC and FISH were performed on the same breast cancer specimens from 388 Korean patients, with a mean follow-up duration of 59.8 months, with survival analyses were made according to the results of the HER2 detection methods; A0485 Ab (DAKO, Denmark) and the HER2 test kit (DAKO HerceptTest(TM), Denmark) for IHC, and the HER2 FISH kit (Vysis Inc., Downers Grove, Ill) for FISH were used. RESULTS: The IHC showed HER2 over-expression rates of 34.8% and 26.8% by the A0485 antibody and HercepTest, respectively. The rate of HER2 amplification by FISH in the same specimen was 25.8%. HER2 was confirmed as an independent prognostic factor by multivariate analyses regardless of the detection methods. In the survival analyses, according to the IHC results for HER2, only the 3+ scoring group in the positive results was associated with a poor survival. However, the positive group in the FISH test revealed a significantly worse survival than the FISH-negative group. CONCLUSION: For the prediction of survival of patients with breast cancer, the FISH test would be more useful than IHC, especially in the 2+ scoring IHC cases.