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A new blood test shows promise in helping physicians better manage the treatment of women
with advanced breast cancer. The CellSearchTM test
measures the number of Circulating Tumor Cells (CTCs) in a sample of blood and can immediately inform physicians
if a patient's treatment is working or needs modification. Such information can be crucial for treating women
with metastatic breast cancer, an advanced form of breast cancer that has potential to spread to other body organs.
The CellSearch test was approved by the U.S. Food and Drug Administration (FDA) in January 2004 and given further clearance
in December 2006 as a routine monitoring test in women with advanced breast cancer. Recent studies presented at
national symposia such as the American Society of Clinical Oncology (ASCO) suggest that the CTC test can help
predict survival and manage treatment. While the test is used independently-typically
following each chemotherapy treatment cycle-health experts do
not recommend that it replace existing tests to monitor disease progression, such as
the CAT scan or PET scan. Instead, it
can be a useful supplement to those tests, which are often administrated every 12 to 24 weeks.
Developed by Immunicon Corporation (www.immunicon.com), and marketed by Veridex LLC (www.veridex.com), a Johnson & Johnson
Company, the CellSearch CTC test is increasingly available at pathology laboratories in the United States. The blood
test costs around $500. According to Immunicon, Medicare and most private insurers cover the test.
Circulating tumor cells are shed by tumors and enter the bloodstream, where they can
spread to other body organs in patients with advanced cancers. The CTC test works by
analyzing the cells in a patient's blood sample to count and characterize them. Studies
published in Clinical Cancer Research, the Journal of Clinical Oncology and the New England
Journal of Medicine suggest that the CTC test can predict survival in patients with advanced breast cancer.
According to Immunicon, if a patient typically has more than five CTCs in a blood sample, survival may be
shorter compared to patients with no CTCs. The CTC test can help physicians monitor a patient's treatment
by determining whether the number of cancer cells is decreasing. This information can help determine whether
changes are needed in a patient's treatment.
Such information is important, particularly for women with advanced breast cancer. About 25% of
women with advanced, metastatic breast cancer survive longer than five years. The most common
region breast cancer spreads to is the bone, followed by the lung and liver. Treatment will
differ depending on the patient's history of treatment and how well she responds to specific
therapies. Chemotherapy or other drug therapies are usually given to advanced breast cancer
patients because they affect the entire body (as opposed to localized treatments that only affect one area).
In addition to breast cancer, researchers are investigating whether the CTC test can
be useful in patients with advanced colon cancer or prostate cancer. Clinical data for those
cancers are expected within the next two years.
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