Kenneth J. Bloom, MD, Chief Medical Officer, Clarient, discusses retesting patients who present with HER2-positive characteristics but receive HER2-negative test results.

Bloom's first choice for HER2 testing for patients with breast cancer is immunohistochemistry (IHC). If the initial test says the tumor is HER2-negative and the patient has characteristics that do not suggest HER2 positivity, such as a low tumor grade, strong progesterone receptor expression, and a low proliferation index, then a second test is not needed.

If the test returns negative and a single positive characteristic is present a second test should be performed. The question that lingers is whether the second test should be performed on the same or a different tissue block. Breast cancer heterogeneity allows for some blocks to test differently than others.

The second test should use a different assay than the first. The test you use first can vary, but Bloom suggests IHC (View more on this topic >>> 

Bloom notes that it is important to test using a second methodology because of the magnitude of improvement seen with the addition of Herceptin.

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Dr. Kenneth Bloom, from Chief Medical Officer at Clarient, Explains Situations Requiring HER2 Retesting

Dr. Bloom Explains Situations Requiring HER2 Retesting

Kenneth J. Bloom, MD, Chief Medical Officer, Clarient, compares the immunohistochemistry (IHC) and FISH assays for use in routine screening for HER2 expression.

Bloom describes that HER2 testing can be very complicated but that several FDA cleared assays have simplified the process. The approved assays were also used in many of the clinical trials investigating HER2 expression, which further demonstrates their efficacy.

Many of the assays provide similar end results. From a pathologists viewpoint Bloom recommends using the immunohistochemistry (IHC) assay first. The results of the IHC test are equivalent to FISH, however he notes that IHC is quicker, easier to perform, and does not require specialized equipment.

The FISH test requires a darkened room, under high power, and irradiates the lab tech. The IHC assay is more conducive to routine screening because it does not have as many complications.

Dr. Kenneth Bloom, the Chief Medical Officer at Clarient, Compares HER2 Screening Assays

Kenneth J. Bloom, MD

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Dr. Bloom Explains Situations Requiring HER2 Retesting

Dr. Bloom Compares HER2 Screening Assays