Breast Cancer Coverage from Every Angle

Update to ASCO/CAP Guidelines on HER2 Testing in Breast Cancer

By: Celeste L. Dixon
Posted: Wednesday, August 22, 2018

The American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) have issued a clinical practice guideline focused update on HER2 testing in breast cancer, published in the Journal of Clinical Oncology. Panel co-chairs were Antonio C. Wolff, MD, of Johns Hopkins Sidney Kimmel Comprehensive Cancer Center, Baltimore, and M. Elizabeth Hale Hammond, MD, of the University of Utah School of Medicine, Salt Lake City.

An expert panel reviewed the published literature as well as research survey results, focusing on “the observed frequency of less common in situ hybridization (ISH) patterns to update the recommendations.” The update’s diagnostic approach “includes more rigorous interpretation criteria for ISH and requires concomitant immunohistochemistry (IHC) review for dual-probe ISH groups 2 to 4 to arrive at the most accurate HER2 status designation (positive or negative) based on combined interpretation of the ISH and IHC assays.”

Here are a few of the key recommendations:

  • The revised definition of IHC 2+ (equivocal) is invasive breast cancer with weak to moderate complete membrane staining observed in > 10% of tumor cells.”
  • “If the initial HER2 test result in a core needle biopsy specimen of a primary breast cancer is negative, a new HER2 test may (not ‘must’) be ordered on the excision specimen based on specific clinical criteria.”
  • “The HER2 testing algorithm for breast cancer is updated to address the recommended workup for less common clinical scenarios (approximately 5% of cases) observed when using a dual-probe ISH assay.”

For the complete recommendations, see link below.

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