FOR PATIENTS
The Test
At Martell we know how hard it is to navigate a cancer diagnosis and that information is power. We want you to be able to be an advocate for your care and treatment. With that in mind we have developed a simple test (HERTEST®) that can detect small amounts of HER2/neu that are shed into the bloodstream. This serum HER2/neu can be detected by an ELISA immunoassay. HERTEST® provides a new look at HER2/neu blood testing using state-of-the-art recombinant monoclonal antibodies.
Clinical Background
The human epidermal growth factor receptor 2 (HER2/neu, ErbB2) is a transmembrane receptor with an extracellular domain (ECD) and intracellular tyrosine kinase activity. Potentially 50,000 HER2/neu molecules may be present on a single cancer cell, when overexpressed or amplified. The molecules then interact and activate cell growth.
Approximately 20% of invasive primary breast cancers and a significantly higher proportion of metastatic tumors overexpress HER2 enough to “drive” the cancer. HERTEST® results with levels of HER2 beyond an upper limit of normal indicate the presence of a HER2 tumor—false positive results are very rare. A rising sHER2/neu may be a bellwether of recurrence, preceding clinical or radiologic evidence by months. Elevated HERTEST® values in the absence of a positive tissue test may signal a role for targeted therapeutics in refractory breast cancer despite an earlier negative tissue test.
Given the cost and limitations of targeted therapy, oncologists are seeking ways to reduce drug use yet improve outcomes and the quality of life. HERTEST® monitoring provides useful information to support cancer treatment de-escalation.
The Evidence
To be of maximum value, blood (serum) tests should fulfill four specific criteria—HERTEST® scores high in all four measures.
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PROGNOSTIC—A high sHER2 correlates with a smaller likelihood of pathological complete response (PCR) and with a shorter disease-free survival.
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PREDICTIVE—An elevated sHER2 predicts response to targeted and cytotoxic drugs.
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Serum HER2 is UNRELATED TO TUMOR SIZE
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Serum HER2 must be considered INDEPENDENTLY OF TISSUE HER2—Tissue negative primary tumors may give rise to HER2 positive metastases, often called a phenotypic shift.
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Free of Recurrence Recurrence Poor Prognosis
Each of the above criteria has been studied extensively. Reports from Germany, Spain, France, the U.S., and elsewhere corroborate monitoring in over 10,000 breast cancer patients.