Blood test may predict breast cancer treatment response
FRIDAY 16 MAY 2008
A blood test that measures the number of cancer cells travelling in a patient's bloodstream could provide a reliable indicator for how well they are responding to treatments for spreading, or metastatic, breast cancer, scientists have found.
The simple test measures the number of circulating tumour cells (CTCs) in the bloodstream and the number of cells, or 'CTC count', can then be used to determine how their disease is progressing.
Researchers at Georgetown University Medical Centre hope that doctors could one day use the test to reliably assess the effectiveness of treatments for patients with metastatic breast cancer so that they can try different treatments more quickly if required.
Dr Minetta Liu, a researcher in Georgetown's Lombardi Comprehensive Cancer Centre, explained: "It can take several weeks and sometimes months to determine if a particular cancer treatment is working because it can take that long to observe any significant radiographic changes in tumour size or appearance.
"With this new blood test, we have another reliable tool that may allow us to determine much sooner if a therapy is ineffective so that we can change therapy earlier and potentially make more significant improvements in survival."
The researchers used a technology called CellSearch to measure the number of CTCs in blood samples from patients with metastatic breast cancer every three to four weeks.
They found a strong link between a woman's CTC count and her degree of disease progression.
Using a CTC count of five as a threshold, they found that women with a CTC count of greater than five were much more likely to have disease progression than those with a CTC count lower than five.
Seventy-one per cent of patients with a CTC count greater than or equal to five had disease progression, and 66 per cent of patients with a CTC count of less than five did not.
Dr Liu revealed: "A CTC count of five or greater at the time of restaging was associated with a 5.32 fold increase in a patient's chance of having disease progression compared to CTC counts of less than five.
"CTC assessments should be used as a surrogate marker for treatment efficacy and disease responsiveness. Changes in CTC results from less than five to greater than or equal to five over time may herald disease progression."
The researchers are now conducting a follow-up study and hope to find more evidence to support the routine use of CTC assessments in patients with metastatic breast cancer.
"We have many treatment options for advanced breast cancer. The key is to find the most effective therapy for each patient," the expert added.
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