Blood Test Can Predict Metastatic Breast-Cancer Survival

Knowing the number of CTCs in a patient's blood may help doctors make critical decisions about treatment earlier than was previously possible. The study results were reported in the August 19, 2004 issue of The New England Journal of Medicine.

The study involved 177 women with metastatic breast cancer who were about to start initial therapy or change to a new therapy. Patients were tested to establish a CTC count before therapy and after a follow-up of three to four weeks. Patients with five or more CTCs per 7.5 ml of blood showed significantly shorter progression-free survival and overall survival, dying in an average of 10 months, than patients with fewer than five CTCs, who lived for more than 18 months. The number of patients with more than five CTCs was reduced from 49% before therapy to only 30% at first followup, suggesting that a number of patients had responded to therapy.

One big advantage of the test is that it costs only a few hundred dollars, much less than positron emission tomography (PET) scans or other imaging tests. The company believes the test will also work with other types of cancer, such as prostate, lung, colorectal, or ovarian cancer. The CTCs almost never appear in patients with nonmalignant tumors or in healthy people, according to the company.

Key to the new findings was the availability of an integrated and automated technology to detect CTCs at extremely low frequencies. The technology was developed by Immunicon Corp. (Huntingdon Valley, PA, USA). In the test, tiny magnetic particles are attached to cells in a vial of patient blood. Then a magnetic field attracts those cells out, and they are scanned by a computer to determine which cells are tumor cells.

Immunicon has granted Veridex LLC (Warren, NJ, USA; www.veridex.com) exclusive worldwide rights to commercialize products incorporating this technology in the cancer field. The company plans to launch these products as the CellSearch System as early as the fall of 2004. The products were cleared earlier in 2004 by the U.S. Food and Drug Administration (FDA).

The results of the test are available within several weeks, which can then help doctors determine whether or not a particular treatment is working and, in effect, allowing them to customize their treatment of individual patients. In contrast, imaging scans can take months to show tumor shrinkage. Although the presence of CTCs in the blood of patients diagnosed with cancer has been reported many times, this is the first time their clinical significance has been demonstrated in a controlled trial.

"The results showed the presence of CTCs to be the strongest independent predictor of progression-free survival and overall survival,” said lead author Massimo Cristofanilli. M.D., associate professor in the department of breast medical oncology at the University of Texas M.D. Anderson Cancer Center (Houston, USA).




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