Changes in HER2 Breast Cancer Testing According to 2007 and 2013 ASCO/CAP Guidelines
Hanna et al have reported that the 2013 update to the 2007 ASCO/College of American Pathologists (CAP) recommendations for HER2 testing in breast cancer did not result in changes in the overall HER2-positivity rate but was associated with a higher rate of equivocal results. Their findings were reported in the Journal of Clinical Oncology.
Study Findings
The study involved patient cases with HER2 testing scores from the largest regional reference laboratory for HER2 testing in Ontario during 2012 and 2014. The number of patients tested increased from 2,201 in 2012 to 2,558 in 2014 (2,278 vs 2,659 tumors), reflecting primary testing of core needle biopsies, which resulted in an increase in the number of repeat tests. HER2-positivity rates remained unchanged at 15.7% vs 15.5%. The number of repeat tests within 6 months increased from 122 (5.5%) to 302 (11.8%; P < .001).
The proportion of immunohistochemistry (IHC) 2+ tumors decreased from 25.3% to 20.3% (P < .001). There was an increase in proportion of equivocal results with in situ hybridization testing in IHC 2+ tumors from 22 of 576 (3.8%) to 82 of 541 (15.2%) and in IHC 0/1+ tumors from 0 of 103 (0%) to 20 of 275 (7.3%; both overall P .001).
The investigators concluded: “Our findings indicate that the 2013 updates to the American Society of Clinical Oncology/College of American Pathologists recommendations for HER2 testing in breast cancer did not affect the overall HER2-positivity rate or the proportion of patients eligible for HER2-targeted therapy. The proportion of tests and repeat tests performed increased, as did the number of patient cases categorized as [in situ hybridization] equivocal. The benefit of targeted therapy in the equivocal group is not proven, so targeted therapy should not be considered for patients in this category, which should be redefined in future iterations of the recommendations.”
The study was supported by F. Hoffmann-La Roche.
Wedad M. Hanna, MBBCh, of the Sunnybrook Health Sciences Centre, University of Toronto, is the corresponding author of the Journal of Clinical Oncology article.
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