[234] ER IHC Testing in Accordance with Guidelines Established the American Society of Clinical Oncology (ASCO) and by the College of American Pathologists (CAP).

Therese Phillips, Anna Strickland, Scott Webster, Rosanne Welcher. Dako North America, Inc., Carpinteria, CA

Background: A recent and important event in the field of breast cancer diagnostics is the publication of consensus guidelines for hormone receptor testing jointly formulated by ASCO/CAP1. As noted by the ASCO/CAP panel, the ER/PR pharmDx™ kit (Dako) is one example of an assay format that meets the clinical and analytical criteria against which laboratories can validate their assays. In this study IHC protocols based on the anti-ER monoclonal antibodies 1D5 (mouse) and SP1 (rabbit) were compared to ER pharmDx staining of breast cancer tissue.
Design: Protocols developed for concentrated versions of 1D5 and SP1 were validated against ER pharmDx according to the recommended procedures. Formalin fixed, paraffin embedded breast cancer specimens were chosen for this purpose based on their ER status (determined from prior screening with ER pharmDx):

ER Status# Specimens (1D5 Study)# Specimens (SP1 Study)
1% - 10% Positive68
> 10% Positive5530

Stained slides were scored by estimation of Percent Positive tumor cells and designation of positive or negative status according to ASCO/CAP guidelines, i.e. a positive specimen must exhibit 1% or more of tumor cells positive for ER.
Results: Both clones showed performance comparable to ER pharmDx staining (overall agreement was 98.8% for 1D5, 100% for SP1). Additionally, both clones exhibited positive agreement greater than 90% and negative agreement greater than 95%, consistent with published performance benchmarks2.

Metric1D5 vs. pharmDxSP1 vs.pharmDx
Overall Agreement98.8%100%
Positive Agreement98.4%100%
Negative Agreement100%100%

Conclusions: These results indicate that anti-ER clones 1D5 and SP1, when used with appropriately optimized and validated protocols, can provide performance consistent with current ASCO/CAP guidelines for hormone receptor testing.
1Hammond et al., 2010, J Clin Oncol 28:2784-2795.
2Fitzgibbons et al., 2010, Arch Pathol Lab Med 134:930-935.
Category: Breast

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 45, Tuesday Morning


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