[311] The Oncotype DX Assay (ODX) May Not Be Required for All Estrogen Receptor (ER) Positive Breast Cancers

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

Background: The ODX is a 21-gene RT-PCR based commercial assay that is being increasingly used in the management of ER positive (+), lymph node negative (-) breast cancers. The assay provides prognostic and predictive information in the form of a recurrence risk score (RS) that separates patients into low, intermediate, or high risk. This study is designed to determine if histologic and conventional immunophenotypic features of breast cancer are able to predict the ODX RS.
Design: Morphologic features of 153 invasive breast cancers from 3 different institutions excised between 2006 and 2009 were compared to the ODX RS. Features examined included Modified Bloom-Richardson score (MBR), ER, progesterone receptor (PR), Her2/neu status and Ki67 proliferation index. ER/PR were analyzed using the Allred scoring system. Allred percentile scores of 0-4 were considered negative for this study. Ki67 was scored based on percent positivity: <10%= low, 11-20% = intermediate and >20% = high. Expression and amplification were evaluated for Her2.
Results: 66 (43%) of the cancers had a low RS, 66 (43%) an intermediate RS, and 21 (14%) had a high RS. A general trend of increasing ODX RS with higher MBR, higher Ki67 proliferative rate, loss of PR, and overexpression of Her2 was noted. 23 (15%) cases were MBR 1, ER+, PR+, Her2-, and low Ki67. 22 of these had a low ODX RS while 1 had an intermediate RS. Analysis of the 21 cases with a high ODX RS revealed the following: 6 cases had an equivocal or unknown Her 2 status and were excluded. Of the remaining cases 9/15 (60%) had a high Ki67 score, 4/15 (27%) were ER-, 8/15 (53%) were PR- (this included all 4 of the ER- tumors), and 6/15 (40%) overexpressed Her2. In fact, 14/15 (93%) had one or more of the following poor prognostic features: high Ki67 score, ER-, PR-, Her2+. In addition, all cases with MBR of 3, high Ki67 and negative PR and all cases with a high Ki67 and positive Her2 had a high ODX RS. Only 1 case with a high ODX RS was ER+, PR+, and Her2-. This tumor had MBR 2 with an intermediate Ki-67.
Conclusions: Carcinomas with a constellation of good prognostic indicators (MBR 1, low Ki-67, PR+, Her2-) are likely to have a low ODX RS while those with a combination of poor prognostic indicators (MBR 3, high Ki67, PR-, Her2+) are likely to have a high RS. Better understanding of the conventional prognostic markers may obviate the need for ODX testing in a subset of breast carcinomas.
Category: Breast

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 24, Tuesday Afternoon

 

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