The earliest FDA approved biomarkers for IHC application were assays to detect the estrogen receptor (ER), progesterone receptor (PR) and HER-2/neu (c-erbB-2). The presence of these biomarkers in breast cancer tissue serves as a diagnostic, prognostic and predictive method to assist pathologists in identifying breast cancer subtypes and determine whether patients are suitable candidates to receive certain targeted therapies such as Tamoxifen (ER positive patients) or Trastuzumab (HER-2 positive patients). The IHC biomarker c-kit (CD117), which is used in the clinic to detect gastrointestinal stromal tumours (GISTs) (Debiec-Rychter et al., 2004), and p63, which is used to detect the presence of basal cells indicative of normal prostate glands (R. B. Shah, Zhou, LeBlanc, Snyder, & Rubin, 2002; Weinstein, Signoretti, & Loda, 2002), are the latest FDA approved single marker IHC-based assays which were approved almost a decade ago in 2004 and 2005, respectively. Since then no other individual biomarker developed for detection in an IHC assay has been FDA …show more content…
As a result, panel biomarker assays are becoming more relevant. Two emerging IHC panel-based assays are Mammostrat by Clarient InsightDx and IHC4 by Genoptix Medical Laboratory. Mammostrat is an IHC-based panel assay that can estimate risk of recurrence in hormone receptor-positive, early stage breast cancer patients which is independent of proliferation and grade. This assay quantifies p53, HTF9C, CEACAM5, NDRG1 and SLC7A5 by a defined mathematical algorithm resulting in a risk index (Bartlett et al., 2012; Bartlett et al., 2010). Similarly, IHC4 is another emerging assay which estimates recurrence risk for early stage breast cancer patients by quantifying IHC measurement of ER, PR, HER2 and Ki-67 using Aqua technology (Cuzick et al.,