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Blood test provides window into treatment of advanced breast cancer
Ann Arbor - A new blood test could change the way doctors treat women whose breast cancer has spread to other parts of their body.
Using a technology that separates the cancer cells circulating in the blood of women with metastatic breast cancer, doctors are able to count these cells and determine within just three to four weeks whether a new treatment is working.
“If you've started a new therapy, three to four weeks later it's usually too early for us to even begin to tell if the therapy is working. With this test, if you have elevated levels of cancer cells in your blood after three weeks of treatment, it's very likely your disease is going to progress quickly and it means probably you're on the wrong therapy,” says Daniel Hayes, M.D., clinical director of the Breast Oncology Program at the University of Michigan Comprehensive Cancer Center.
Traditionally, the most reliable way to determine if a therapy is effective is to run CT scans, bone scans and chest X-rays. But it takes three to four months of treatment before those tests will show if the treatment is making a difference. Other methods, such as examining the patient or running other blood tests, are usually not accurate.
The idea of counting cancer cells in the blood is not new, but the techniques used until this point have been unreliable. This new method, using a technology called CellSearch, produces the same results every time. CellSearch was developed by Immunicon Corp. in Huntington Valley, Pa., and is marketed by Veridex LLC, a Johnson & Johnson company.
About 250,000 women will be diagnosed with breast cancer this year, and 15 percent to 20 percent of patients will ultimately develop metastasis. Breast cancer most commonly spreads to the liver, lungs or bones.
“Once a patient has developed metastatic breast cancer that we can find in the bones, the liver or the lung, we rarely, if ever, cure such a patient. We can treat her, but not as well as we'd like. And our goal of therapy for such a patient is to keep her quality of life as good as it can be, for as long as it can be,” says Hayes, professor of Internal Medicine at the U-M Medical School.
Treatment involves hormone therapy or chemotherapy, and oncologists have many different options to choose from. If one therapy proves ineffective, doctors may be able to switch the patient to a different treatment.
“The clinician has two challenges,” Hayes says. “One is which therapy is likely to work – and there may be several – with the fewest side effects. Then we have to wait and see whether that was the right choice because these therapies don't work in 100 percent of patients. And so the second challenge is, as a doctor, did I pick the right therapy to achieve that balance?”
The benefit of this new test is patients would not have to spend months taking a drug – and dealing with its side effects – if it's not working.
In a multicenter trial of the CellSearch technology, published in August in the New England Journal of Medicine, researchers at U-M and elsewhere found that in women who had elevated circulating tumor cell levels three to four weeks after beginning a new therapy, the cancer progressed within three months, compared to almost seven months progression-free for women with lower tumor cell levels. The women also had shorter survival when tumor cell levels were elevated: 10 months survival in the elevated group, compared to more than 18 months if levels were low.
“I really think this could help us change the way we treat patients with metastatic disease by making better decisions and treating them more efficiently. By not prolonging therapy that's not likely to work, we can go to therapy that might be more likely to work,” Hayes says.
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U-M Cancer AnswerLine™: (800) 865-1125