SP3, an Alternative to HercepTest in Determining HER-2/Neu (H2N) Status in Breast Cancer Patients with Significant Cost Savings.
Timothy M D'Alfonso, Yi-Fang Liu, Stefano Monni, Sandra J Shin. Weill Cornell Medical College, New York
Background: Accurately determining H2N status in breast cancer patients who may be eligible for trastuzumab treatment in the most cost- and time-effective ways is increasingly important in light of rising healthcare costs. The FDA-approved HercepTest (Dako) is widely used to determine H2N status by immunohistochemistry (IHC) in these patients. SP3, a rabbit monoclonal antibody, is an immunostain that can be performed at a fraction of the cost of using HercepTest. We set out to compare the reliability of using SP3 vs. HercepTest compared to fluorescence in situ hybridization (FISH). Needle core biopsies (NCB) and subsequent excisional biopsies (EXBX) of the same tumor were concurrently studied to also evaluate intratumoral staining heterogeneity as a potential cause for discordance in different sized specimens of the same tumor using these antibodies.
Design: 100 patients with invasive breast carcinoma in NCB and subsequent EXBX were identified. On all 200 patients' specimens, IHC was performed with SP3 and HercepTest and dual-color FISH for H2N amplification on sequential unstained tumor sections. A cost analysis was performed based on current ASCO/CAP practice guidelines for assessing H2N.
Results: Concordance with FISH, and sensitivity and specificity for detecting H2N overexpression by SP3 and HercepTest are shown:
|FISH concordance (%)||Sensitivity (%)||Specificity (%)|