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Breast Cancer Meeting Highlights News fro recent ASCO and San Antonio Meetings

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Old 05-18-2014, 01:52 PM   #1
'lizbeth
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Post Changing pattern for HER2 positivity due to updated ASCO/CAP guidelines for HER2 test

Abstract No:
523
Attend this session at the
2014 ASCO Annual Meeting!


Session: Breast Cancer - HER2/ER
Type: Poster Highlights Session
Time 1: Sunday June 1, 8:00 AM to 11:00 AM
Location 1: E354b

Time 2: Sunday June 1, 11:30 AM to 12:45 PM
Location 2: E Arie Crown Theater
Personalize your Meeting experience with a suggested or customized itinerary!

Author(s): Mithun Vinod Shah, Anne E. Wiktor, Reid G. Meyer, Kathleen S. Tenner, Karla V. Ballman, Rhett P. Ketterling, Edith A. Perez, Robert B. Jenkins; Mayo Clinic, Rochester, MN; Mayo Clinic, Jacksonville, FL
Abstract Disclosures

Abstract:

Background: ASCO/CAP guidelines for HER2 testing in breast cancer were published in 2007 and updated in 2013. HER2-directed therapies (HDT) should be recommended in patients who are deemed HER2 positive, while they are not recommended in HER2 negative patients. If HER2 testing is equivocal, the guideline suggests that HDT be considered. It is not known how implementation of updated guidelines will change clinical practice. Methods: After the implementation of the 2013 guidelines, 321 breast tumor samples were received by the Mayo Clinic Cytogenetics laboratory for FISH analysis of HER2 status. The prevalence of HER2 alterations in this cohort was analyzed using both 2007 and 2013 guidelines. We also retrospectively analyzed HER2 data from N9831 (Alliance), a prospective multicenter randomized trial that evaluated the use of trastuzumab in the adjuvant setting. The trial included 3,505 women with histologically confirmed node-positive/high-risk node-negative HER2 positive invasive breast cancer. US FDA criteria were used to define HER2 positivity in N9831. Results: Using 2007 guidelines, 44 (14%) of the Mayo clinical practice cases were HER2 positive, 262 (82%) negative, and 11 (3.5%) equivocal. Using 2013 guidelines, 80 (25%) were positive, 225 (70%) negative, and 12 (4%) equivocal. The interpretation changed in 48 (15%) cases (p< 0.0001). In N9831 using 2007 guidelines, 2,878 cases were HER2 positive (80.7%), 607 negative (17%), and 80 (2.2%) equivocal. Using 2013 guidelines, 2,937 (82.4%) were positive, 538 (15.1%) negative, and 90 (2.5%) equivocal. The increase in the prevalence of positive cases was significant (p<0.0001). Preliminary analysis suggests no disease-free survival benefit in women who had change in classification when stratified by whether they received HDT or not. Conclusions: There is a significant increase in the proportion of HER2 positive cases when breast cancer specimens are assessed using the 2013 ASCO/CAP guidelines. The updated guidelines also result in more equivocal cases requiring reflex testing. Interpreting HER2 status using updated guidelines will result in an increase in the number of breast cancer patients eligible for HDT. Clinical trial information: NCT00005970.
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