A new study of women with advanced breast cancer who have more tumor cells circulating in their blood deteriorate and die quicker than women with fewer of these cells, according to the researchers from the University of Michigan Comprehensive Cancer Center and other cancer centers throughout the country.
These researchers found that about half of 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 appear in this week's 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.
Survival rates for women with metastatic breast cancer are low, and 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 CellSearchTM 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 CellSearchTM system was developed by Immunicon Corp. in Huntingdon Valley, Pa., and is marketed by Veridex, LLC, a Johnson & Johnson company.
Twenty centers across the country participated in the trial, which prospectively enrolled 177 women with breast cancer that had spread to other parts of the body. All the women in the study were beginning a new systemic treatment, such as chemotherapy or hormone therapy.
In a control group of 345 women without breast cancer, only 1 percent had any circulating tumor cells in their blood. In contrast, 61 percent of the women with metastatic breast cancer had two or more circulating tumor cells.