[188] ER/PR and Her2/Neu Correlation between Immunohistochemisty and Gene Expression Profiling in Women with Invasive Breast Cancer

M Dydo, J Shutter. University of South Florida, Tampa, FL

Background: Mammaprint® is a 70 gene FDA approved gene expression profile used to stratify invasive breast cancer patients into recurrence risk categories using fresh tissue(Figure 1). This test also produces ER/PR and Her-2/Neu gene signatures. The purpose of this pilot study was to correlate the results of routine quantitative immunohistochemisty (IHC) of ER/PR and Her2/Neu protein expression to that of Mammaprint® gene expression profiling.

Design: Fresh tissue was sent for Mammaprint® analysis on 29 patients treated at the University of South Florida Breast Health Center with suspected or biopsy proven diagnosis of invasive breast cancer from 6/09 through 9/09. Fresh tissue samples were obtained by core biopsy or at the time of surgical excision. A gene expression profile for ER/PR and Her-2/Neu was included in the analysis where tumor volume was sufficient (> 30% tumor/connective tissue ratio). The remainder of the tissue was routinely processed for pathologic analysis and evaluation of ER/PR and Her-2/Neu status was performed by IHC. ER/PR was considered positive for ≥ 1% positive nuclear staining.
Results: ER/PR and Her2/Neu data were obtained for both Mammaprint® and IHC for 15 patients. Thirteen out of 15 (87%) cases were ER/PR concordant when comparing IHC to Mammaprint® results (Table 1). The two discordant cases were ER/PR positive by Mammaprint® and ER/PR negative by IHC. All cases were Her2/Neu concordant (Table 2).

IHC vs Mammaprint
ER/PR -20
Table 1

IHC vs Mammaprint
Her-2/Neu +Her-2/Neu -
IHCHer-2/Neu +2N/A
Her-2/Neu -N/A15
Table 2

Conclusions: This study indicates a high but not uniform concordance between IHC and fresh tissue gene expression profiling and suggests that gene expression profiling performed on fresh tissue may be more sensitive for the detection of ER/PR status. When discordant results between these two methodologies arise, it is unclear how clinicians may interpret the data and what effect interpretation may have on therapeutic decisions, prognosis and outcome. Larger studies with long-term follow up may answer these clinically relevant questions.
Category: Breast

Monday, March 22, 2010 1:00 PM

Poster Session II # 60, Monday Afternoon


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