Tumor Cell Levels
in Blood Predict Success of Advanced-Stage Breast Cancer Treatment
Behind the Cancer Headlines®
Women with advanced breast cancer who have a higher number of tumor cells circulating in their blood progress more rapidly and die sooner than women with fewer of these cells, according to a new study by researchers from the University of Michigan Comprehensive Cancer Center and other cancer centers throughout the country.
The researchers determined that about half of the 177 women in the study whose breast cancer had metastasized, or spread, and who were starting a new treatment had elevated levels of circulating tumor cells in their blood system. Investigators defined an elevated level as five or more tumor cells in a sample of blood.
Of those women, 30 percent still had higher numbers of circulating tumor cells three to five weeks after beginning a new treatment and their cancer progressed very rapidly compared to women whose tumor cell levels dropped during that time or who never had elevated circulating cell levels.
The study was performed using a newly developed technology called CellSearchTM that isolates and characterizes these cells. Results of the study were published in the New England Journal of Medicine.
"Identifying the number of circulating tumor cells in patients with metastatic breast cancer, especially at the time of their first follow-up after starting new therapy, may provide an early, reliable indication of whether that therapy will be successful," says senior study author Daniel Hayes, M.D., clinical director of the Breast Oncology Program at the University of Michigan Comprehensive Cancer Center.
The goal of treatment is to slow the tumor's growth and decrease its size so symptoms lessen. Currently, to determine if a therapy is effective, patients often must wait three to four months after beginning the treatment and then undergo a series of tests, including bone scans and X-rays.
If the technique used in this study is proven effective, doctors could determine within several weeks if the therapy is working, with only a routine blood draw for the patient.
When cancer spreads, or metastasizes, it travels through
either the lymph channels or the bloodstream. By filtering the blood,
researchers can identify the cancer cells, called circulating tumor cells, in
transit. The CellSearch™ technique involves mixing a
blood sample with iron particles coated with an antibody that attaches to
epithelial cells like those found in breast tissue. The cells are further
characterized with other antibodies that have been tagged with a fluorescent dye,
so that the cancer cells can be easily distinguished and counted. Since
epithelial cells are not typically found in blood, their presence suggests they
are cancerous cells from the breast tissue. The CellSearch™
system was developed by Immunicon Corp. in
Researchers are currently considering a follow-up study to assess whether changing therapies can improve outcomes. At the current time, circulating tumor cell levels should not be used as a standard test to change therapy, but they may be considered within the context of other clinical, radiographic and blood testing, says Hayes.
He also cautions that circulating tumor cells cannot be used
as a screening test for breast cancer, nor does the study have any implications
for women diagnosed with non-metastatic
cancer.
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