Reliability of HER2 testing from core needle biopsies

June 7, 2010

A recent study analyzed the reliability of testing for HER2 status from Core Needle Biopsies (CNBs) versus surgical specimens from five pathology laboratories.  Accurate testing of HER2 status is important for correctly identifying patients who would benefit from HER2 targeted therapy such as trastuzumab and those who would not.  The two most commonly used tests include:  immunohistochemistry (IHC), which looks for abnormalities in protein (receptor) overexpression, and fluorescence in situ hybridization (FISH), which looks for abnormalities in gene amplification.

There is controversy surrounding the lack of standardization for HER2 testing.   In response to the lack of standardization in IHC testing, the US Food and Drug Administration approved and developed IHC scoring criteria. Similarly, the College of American Pathologists (CAP) and the American Society for Clinical Oncology (ASCO) jointly developed guidelines to improve the accuracy of HER2 testing.

The current study evaluated the reliablilty of IHC testing on 500 CNBs cases of primarily diagnosed breast cancer as compared with the corresponding surgical specimens. The study also evaluated the implication of the new ASCO-CAP evaluation criteria compared to the US FDA–approved scoring criteria for these cases. IHC scores at the highest level (3+) for the CNBs cases were consistent in four of the five participating institutions if scoring followed the ASCO-CAP criteria. In addition, the researchers also found that for those CNBs with IHC score levels in the mid range (2+), accurate results for HER2 status could be obtained by retesting with the FISH method.