How is it used?
After a diagnosis of metastatic
breast cancer has been made, Her-2/
neu testing may be used as a marker to help determine how aggressive the breast cancer tumor is likely to be. It is usually ordered along with
estrogen and progesterone hormone receptor status tests (ER and PR). The results of these three tests give the doctor information about the person's likely prognosis and response to specific therapies such as hormone therapy and chemotherapy.
The Her2/neu test is sometimes used to monitor Her2/neu-positive breast cancer patients who are receiving cancer therapy including, for example, hormone therapy, chemotherapy, or Her-2/neu targeted therapy. If the level of serum Her-2/neu is initially elevated (greater than 15 ng/mL) then falls, it is likely that treatment is working; if it stays elevated, treatment is not working; and if the level falls then rises, the cancer may be recurring.
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When is it ordered?
Her-2/
neu testing is recommended along with
estrogen and progesterone receptor status testing as part of an initial workup of invasive
breast cancer and is sometimes performed with recurrent breast cancer. It is not diagnostic but helps the doctor determine treatment options and understand more about the tumor's characteristics.
Her-2/neu is sometimes ordered initially to establish a baseline concentration and then, if elevated, ordered periodically to monitor cancer treatment. Occasionally it may be ordered to help determine a cancer's Her-2/neu status when there is insufficient tumor tissue available to perform tissue testing.
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What does the test result mean?
If an IHC Her-2/
neu test is positive, it means that the Her-2/
neu gene is
over-expressing the Her-2/
neu protein. If a FISH test is done, then
amplification of the Her-2/
neu gene can be detected. If either of these is positive, then the person is likely to have a tumor that is aggressive, that will respond poorly to endocrine treatment, and that will be resistant to chemotherapy. These people may be considered candidates for tratuzumab (Herceptin) therapy, a drug that was created to target Her-2/
neu protein.
If the IHC is negative but the FISH is positive, the person still may benefit from Herceptin, but if both are negative the treatment will not be useful.
If a breast cancer is Her-2/neu-positive and the serum Her-2/neu is initially elevated, then changes in serum Her-2/neu levels can be used to help monitor the effectiveness of Herceptin treatment and detect early disease progression. Decreases indicate a response to treatment; levels that stay the same or increase indicate that the treatment is not effective; concentrations that fall, then rise may indicate a cancer recurrence. If the serum Her-2/neu is initially negative or low, such as may be seen with early cancers and with Her-2/neu-negative cancers, then it may not be useful as a monitoring tool.
Some studies have shown that there can be differences in Her-2/neu positivity between the primary tumor and tumor that has spread to other parts of the body. If a patient who has breast cancer is determined to be Her-2/neu negative when the primary tumor is tested but then has a serum Her-2/neu level greater than 15 ng/mL, then additional testing of tissue may be indicated.
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Is there anything else I should know?
Her-2/
neu-positive tumors are susceptible to Herceptin (tratuzumab). Herceptin attaches itself to the excess protein molecules and inhibits the growth of the cancer. The development of this specialized therapy has increased the use of Her-2/
neu testing. Herceptin may be used alone or with some chemotherapy agents but is only useful in those who have Her-2/
neu and protein .
Her-2/neu testing is not available in every laboratory. Both IHC and FISH require experience and special training to perform and interpret. Your doctor will probably send your sample to a reference laboratory and the results may take several weeks to return.
It takes a small amount of cancer tissue to perform the Her-2/neu test. If a sufficient sample is not available, your doctor may try running a serum Her-2/neu test and/or make an assumption that you are Her-2/neu-positive in order to broaden your treatment options.
The Her-2/neu gene is also amplified and its protein is over-expressed with some other cancers, such as ovarian and bladder cancer.
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