Small amounts of HER2/neu are shed into the bloodstream and can be detected by an ELISA immunoassay. HERTEST provides a new look at HER2/neu blood testing using state-of-the-art recombinant rabbit monoclonal antibodies.
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.
To be of maximum value, blood (serum) tests should fulfill four specific criteria—HERTEST scores high in all four measures.
PROGNOSTIC—A high serum HER2 correlates with a smaller likelihood of pathological complete response and with a shorter disease-free survival.
PREDICTIVE—An elevated serum HER2 predicts response to targeted and cytotoxic drugs.
Serum HER2 is UNRELATED TO TUMOR SIZE
Serum HER2 must be considered INDEPENDENTLY OF TISSUE HER2—Tissue negative primary tumors give rise to HER2 positive metastases, often called a phenotypic shift.
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.