Validity of immunohistochemistry method in predicting HER-2 gene status and association of clinicopathological variables with it in invasive breast cancer patients

Abstract

Human epidermal growth factor receptor-2 is an important and prognostic factors and one of the most targeted proteins in breast cancer's therapy. There is no globally accepted method for determining its status. Here, we aimed to evaluate the immunohistochemistry method validity in predicting HER-2 status by Fluorescence in situ hybridization method and investigate some clinicopathological variables association with HER-2 amplification. A total of 190 HER-2 2+ and 3+ by immunohistochemistry (IHC) invasive breast cancer cases were enrolled in this study. Fluorescence in situ hybridization (FISH) was performed for these cases using FDA criteria and the association between clinicopathological variables and HER-2 status evaluated. Study consisted of 190 invasive breast cancer patients (160 HER-2 2+ and 30 HER-2 3+). HER-2 FISH amplification according to FDA criteria was found 27.5 (44/160 patients) in HER-2 2+ patients and 83.3 (25/30 patients) in HER-2 3+ patients. Tumors with HER-2 amplification were more likely to be ER-negative (51.0 vs 31.2, p = 0.013) and PR-negative (52.9 vs 27.0, p < 0.001). This study showed that immunohistochemistry is not a good method for evaluating HER-2 status and decision-making about trastuzumab therapy even with 3+ score patients. However, this result may not be too strong for IHC 3+ cases due to the limited number of these patients in this study.