[137] 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 (%)
SP3 NCB	91	69.2	93.8
HercepTest NCB	92	61.5	87.5
SP3 EXBX	90	69.2	95
HercepTest EXBX	90	69.2	96.2

Using HercepTest and SP3, 15 and 8 NCB, respectively, showed 2+ staining and were reflexed to FISH. For 100 patients studied, the cost for assessing H2N status using a combination of SP3 ($7 per test) and FISH ($290 per test) was $3,768, compared with a cost of $17,879 for HercepTest ($114 per test) and FISH. Intratumoral staining heterogeneity for both antibodies was negligible in NCB and EXBX of the same tumor.
Conclusions: SP3 is comparable to HercepTest with respect to agreement with FISH, and sensitivity and specificity for detecting H2N overexpression. The use of SP3 obviated the need for FISH in a number of cases which when coupled with this less costly antibody produced a total cost savings of $14,111 in the 100 patients studied. SP3 is a reliable alternative to HercepTest for determining H2N status while providing significant cost savings.
Category: Breast

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 55, Tuesday Morning