Metastatic Breast Cancer

Aids in Making Decisions About Your Care

Treatment for metastatic breast cancer involves routine testing, and although the need for frequent testing may seem inconvenient, it is essential for keeping track of the disease’s response to treatment. If testing shows that the cancer is not slowing or stopping the growth of breast cancer cells, one of the many other treatment options can be started. Beyond the obvious advantage of not continuing an ineffective treatment, testing can help enhance your quality of life by avoiding the side effects of treatment that is not working.

For women with metastatic breast cancer, response to treatment can be monitored with several different tests, and most often, more than one test is needed for accurate assessment. These tests include imaging studies, tumor markers, and a blood test that measures the number of circulating tumor cells in a tube of blood. One or more of these studies should be done before treatment begins so that your doctor has a baseline for comparison with later studies.

You will also have routine visits with your doctor during treatment, and the history and physical examination are other important elements in monitoring response. Be sure to tell your doctor if you are having any symptoms or if symptoms have lessened. Relief of pain, easier breathing, or increased energy may be signs that the cancer is responding. Depending on the sites of metastasis, your doctor may be able to determine with a physical examination if the treatment is working; for example, if a lymph node is a site of metastasis, your doctor may be able to feel that the node has decreased in size, indicating that the metastasis has shrunk.

Taken together, a routine history and physical examination and the results of specific testing can enhance your health care by helping you and your doctor make more informed decisions about your treatment.

Imaging Studies

Many imaging studies are available to help detect response of metastatic breast cancer to treatment. Imaging studies are typically done beginning about 12 weeks after the start of treatment and allow the doctor to measure the size of a tumor or metastatic site. A tumor or metastatic lesion that is smaller than it was before treatment is evidence of a response. Potential imaging studies include bone scans, x-rays, computerized tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET). The specific imaging study done depends on the location and extent of the metastasis. Imaging studies are painless, and there are no side effects.

Bone Scan

Bone scans are used to determine whether metastatic bone disease is responding to treatment. A small amount of a radioactive substance is injected into a vein in the arm just before the procedure is to be done; this radioactive substance will collect in areas of metastatic disease. A special camera is then used to record images of areas with an increased amount of the radioactive substance. Most of the radioactive substance will be eliminated from your body within one day and it will be completely gone within two days.

X-ray

X-rays are used primarily to monitor response of metastatic lesions in the lungs. X-rays may be useful for detecting lesions elsewhere in the body, but other imaging studies may be needed for verification.

CT Scan

A CT scan, which provides three-dimensional x-ray images of internal organs, can be used to monitor response of metastatic lesions in the lung or liver. During the procedure, the table on which you’re lying will move slowly through the CT scanner. Sometimes, a contrast material is injected into a vein before the test to enhance the quality of the images.

MRI

With MRI, images are produced through radiowaves and a powerful magnet linked to a computer. MRI is of most value for assessing response in the brain, spine, and bone. An MRI machine is similar to a large tube, and you will need to lie still on a table within the tube. If you are claustrophobic, tell your doctor, as it may be helpful for you to receive medication to decrease anxiety. Talk to the MRI technologist about any concerns or fears, as he or she can help you find ways to relax. The MRI machine will make loud, repetitive clicking noises during the procedure. As with CT scans, contrast material may be injected before the procedure to enhance the images.

PET Scan

A PET scan is a specialized imaging exam in which a small amount of radioactive glucose (a type of sugar) is injected into a vein. Breast cancer cells use a high amount of energy and will therefore absorb great amounts of the radioactive sugar. The special camera in a PET scan machine will detect the increased amounts of radioactive sugar, providing images of the area of metastasis. PET scans are not usually done routinely, but they may be of benefit if the findings of other imaging studies are inconclusive.

Tumor Markers

Tumor markers are substances (usually proteins) that are abnormally expressed in the body when cancer is present. These substances are either produced by cancer cells themselves or by other cells in response to cancer and can be found in the blood or tumor tissue. Tumor markers can serve distinct purposes. Hormone receptors (estrogen receptor [ER] and progesterone receptor [PR]) and human epidermal growth factor receptor 2 (HER2, a protein linked to higher aggressiveness in breast cancers) status help physicians guide treatment, whereas cancer antigens help monitor response. The three cancer antigens associated with metastatic breast cancer are cancer antigen 15-3 (CA 15-3), cancer antigen 27.29 (CA 27.29), and carcinoembryonic antigen (CEA).

Hormone Receptors and HER2

Testing for ER, PR, and HER2 are done on samples taken from the primary tumor or a metastatic lesion. The results of this testing is of immense value, as it identifies the breast cancers that are most likely to respond to hormone therapy (ER and PR status) and anti-HER2 treatment (HER2 status). The hormone status and HER2 status are so important in guiding treatment that two national cancer organizations—the American Society of Clinical Oncology (ASCO) and the National Comprehensive Cancer Network (NCCN)—have recommended that these tests be done on all invasive breast cancers at the time of diagnosis. If you have metastatic disease that is a recurrence of earlier breast cancer, your doctor can use the information from testing at the time of the original diagnosis; if testing was not done at that time, testing should be done on a biopsy sample from a metastatic lesion. Similarly, testing should be done on a biopsy sample if metastasis is present at the time of first diagnosis. Testing should be done only at accredited laboratories. Talk to your doctor about the accuracy of the test results.

Cancer Antigens

CA 15-3, CA 27.29, and CEA are found in approximately 50% to 90% of women with metastatic breast cancer. However, the results of testing of these markers are not definitive; low levels may not correspond with response, and high levels may be a sign of a condition other than cancer. Because of this, ASCO recommends that these tumor markers should not be used alone to monitor response; imaging studies should also be done to confirm or refute the findings of tumor marker testing.

Monitoring response with these tumor markers usually begins 3-4 months after treatment has begun because levels may be falsely elevated in the first several weeks after the start of treatment. Tumor marker testing is done on a small sample of blood drawn from a vein (usually in the arm).

Circulating Tumor Cells

A recently developed technique offers additional benefits when used in conjunction with imaging and other clinical markers of disease. The technique involves measuring the number of circulating tumor cells (CTCs) in the bloodstream. CTCs are intact cells that are thought to detach from metastatic tumors and enter the bloodstream. Studies have shown that the number of CTCs in the blood correlates to progression-free survival and overall survival. Thus, knowing the number of CTCs (the CTC count) can help you and your doctors make a more informed decision about your care.

The CellSearch® Circulating Tumor Cell (CTC) Test (Veridex, a Johnson & Johnson company, Raritan, NJ) is a simple blood test that captures and counts the number of CTCs in a tube of blood. The CellSearch® System is used in the United States for women who have metastatic breast cancer. (The test is also used for metastatic colorectal cancer and metastatic prostate cancer.)

It may be several weeks and sometimes months before response to treatment can be detected by imaging studies, and, as noted, tumor marker levels are usually first determined about 3-4 months after the start of treatment. Although the CTC test cannot be used to determine response to treatment, CTC counts can give your doctors an early indication of how you are doing. The primary benefit of using CTC counts is that it allows your doctors to assess your prognosis at any time during the course of the disease. A CTC count that either stays below 5 or decreases to below 5 over time indicates a more favorable prognosis compared with a CTC count that remains at 5 or increases to 5 or more over time. It is important to note that as many as 40% of individuals with progressive metastatic cancer will have undetectable CTCs in their blood. CTC counts should be used in conjunction with imaging studies and other clinical markers.

This innovative technology was honored with the Prix Galien USA 2009 Award for Best Medical Technology.

 http://www.prix-galien-usa.com/_pdf/090930.pdf

Talk to Your Doctor

No single test provides the complete picture regarding response to treatment. Women with metastatic breast cancer should talk to their doctors about the testing that is most appropriate for their individual situation. Your doctor will work with you to determine not only what kind of testing is best but also how often it should be done. Some questions to ask your doctor are the following:

• Which tests do you recommend for monitoring response to treatment?
• How often should these tests be done?
• How long does it take for the results to be ready?
• How are the results of these tests interpreted?
• Is there anything that interferes with obtaining an accurate result with these tests?
• Are there clinical trials available in which these tests are being evaluated?

Table 1. Markers that Aid in Determining Treatment for Metastatic Breast Cancer

Additional Sources of Information

• American Society of Clinical Oncology's Patient Web Site: www.cancer.net
    What to Know: ASCO's Guideline on Tumor Markers for Breast Cancer
• Living Beyond Breast Cancer: www.lbbc.org
    Guide for the Newly Diagnosed
• Veridex: www.veridex.com

   

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