Pathology Associates
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HER2 Testing

Clint Blasingame - Monday, December 16, 2013 | Comments (0)

In November, 2013 (and issued several weeks earlier as an early on-line release), The American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) issued a joint, updated guideline aimed at improving the accuracy and reporting of human epidermal growth factor receptor 2 (HER2) testing in patients with invasive breast cancer. 

The guideline, originally issued in 2007, provides new and revised recommendations on HER2 testing to identify patients who can benefit from effective HER2-targeted therapies, such as trastuzumab (Herceptin), pertuzumab (Perjeta), lapatinib (Tykerb), and T-DM1 (Kadcyla). These treatments can substantially improve survival in patients with HER2-positive invasive breast cancer. It is important to accurately determine the HER2 status to ensure that patients most likely to benefit are offered an HER2-targeted treatment, and those that are unlikely to benefit can avoid costs and side effects associated with those drugs.

The new guideline revised scoring for HER2 immunohistochemistry (IHC) stains and also revised scoring cutoffs for HER2 in-situ hybridization (ISH) testing. It also increased the upper end of the range of optimal fixation time for specimens used for HER2 testing to 72 hours.  Testing is now recommended for primary invasive breast carcinomas, recurrences, and metastases. In addition, the new guideline stresses repeat testing if HER2 results are discordant with other clinical or histologic findings. If a patient’s initial tumor was HER2 negative and a patient has disease recurrence with clinical behavior suggesting of HER2 positive or triple negative disease, repeat HER2 testing should be strongly considered. Repeat testing should be performed for tumors with discordance between histologic findings and HER2 results (i.e. a low grade tumor that is HER2 positive).  Repeat HER2 testing should be performed on tumor-containing excisions if a prior biopsy showed high grade (grade 3) tumor that was HER2 negative (0 or 1+), if the amount of tumor in the prior biopsy was small, if the re-excision specimen contains high grade tumor morphologically different from the tumor in the initial biopsy, if HER2 by IHC and FISH testing was equivocal (2+) in the initial specimen, or if there is doubt about appropriate handling of the prior specimen or about test results of the prior biopsy specimen.

Pathology Associates implemented the updated ASCO/CAP guideline recommendations soon after their release. Our laboratory is accredited by the College of American Pathologists.  In addition to strict quality control measures for our HER2 stains, we participate in laboratory inspections and proficiency testing as well as perform ongoing validation of our breast panel (ER,PR,HER2) results to ensure reliability and accuracy of our test results.  
 
References: 
http://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2013-0953-SA   

(Archives of Pathology 137(11)2013) 
Clinical Oncology 31(31) 2013: 3997-4013

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