[180] Comparative Analysis of Breast Prognostic Indicators by Immunohistochemistry (IHC) and Oncotype DX (ODX)

F Dadmanesh, B Obadia, S Apple, J Shiffer, P McAndrew, E Wolin, S Bose. Cedars Sinai Medical Center, Los Angeles, CA; UCLA Medical Center, Los Angeles, CA; Kaiser Permanente Medical Center, Woodland Hills, CA

Background: ODX, a reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assay of 21 selected genes performed in parafin-embedded tumor tissue, predicts the risk for distant recurrence among patients with lymph node negative, estrogen receptor (ER) positive breast cancer treated with tamoxifen. Patients with low recurrence score (<18) do not benefit from chemotherapy treatment. A comparative study of ER, PR and Her2 neu results obtained by IHC and RT-PCR (ODX) is performed.
Design: ER, PR, Her2-neu status defined by IHC and ODX were reviewed in 89 breast cancer cases collected between 2007 and 2009 from differents laboratories. Results of IHC and RT-PCR (ODX) were compared.
Results: Results from both assays are summarized in table1. Discrepancy was observed in 2 cases for ER(2%), 7 cases for PR (7%). No discrepancy was observed for Her2 when IHC and FISH results were combined. 2 ER negative cases by ODX showed weak (1-2+) positivity by IHC in less than 10% of tumor cells. 3 of 4 PR negative cases by ODX showed weak (1-2+) positivity by IHC in less than 50% of tumor cells. 3 of 11 PR negative cases by IHC were positive by ODX, however, the positivity was borderline (5.7-6.3). All 12 cases with equivocal Her2 positivity by IHC were negative by ODX and FISH. Also both cases with negative Her2 by IHC and equivocal positivity with ODX were negative by FISH.

Table 1
IHCnumber of casesODX +ODX -ODX equivocal
ER +88862
ER -101
PR +78744
PR -1138
HER2 +5221
HER2 -72572
HER2 equivocal1212

Conclusions: IHC results are comparable to RT-PCR (ODX). Discrepancies were observed in only a minority of cases, occuring most often in PR results. Therefore, use of a costly test such as ODX is not necessary to determine the status of ER, PR and Her2-neu.
Category: Breast

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 30, Tuesday Afternoon


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