Laboratory Testing for HER2/neu in Breast Carcinoma: An Evolving Strategy to Predict Response to Targeted Therapy

Nils M. Diaz, MD, Interdisciplinary Oncology Program at the H. Lee Moffitt Cancer Center & Research Institute at the University of South Florida, Tampa, Florida. Submitted July 1, 2001; accepted August 9, 2001

Cancer Control. 2001;8(5) 

In This Article

An Evolving Strategy for Determining HER2/neu Status

A consensus is evolving that a useful strategy for determining whether anti-HER2/neu therapy should be offered to a patient in appropriate clinical circumstances include both IHC and FISH analysis. Such a strategy will require modification according to which laboratory testing methods best predict response to available and future anti-HER2/neu-directed therapies. Specifically, IHC should presently be used as a screen for overexpression of the oncoprotein based on the following factors: (1) IHC is less expensive, more routine in clinical laboratories, and less labor intensive than FISH, (2) IHC has a high concordance with FISH when the result is negative (0 or 1+) or strongly positive (3+), and (3) studies have, as yet, not shown that nonoverexpressors -- 0 or 1+ by IHC but FISH-positive -- benefit from targeted therapy. If the IHC result is weakly positive or indeterminate (2+), testing the carcinoma by FISH for gene amplification is recommended to help in selecting patients for the anti-HER2/neu therapy trastuzumab.

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