Medical Device Daily

A new study using the Veridex (Raritan, New Jersey) CellSearch System has provided further evidence that measuring the change in circulating tumor cell (CTC) counts can accurately predict the prognosis and survival of patients with metastatic breast cancer.

"The study results suggests that, in the future, maybe we should try to look more specifically at real-time monitoring of CTC counts in place of imaging or accompanying imaging to save money for healthcare," lead study author Massimo Cristofanilli, MD, associate professor in the Department of Breast Medical Oncology at The University of Texas M.D. Anderson Cancer Center (Houston), told Medical Device Daily.

The Veridex CellSearch System is the first 510(k) diagnostic test used to automate the capture and detection of CTCs, which are tumor cells that have detached from solid tumors and enter the blood.

Veridex acquired the technology last year when it purchased the assets of Immunicon (Huntingdon Valley, Pennsylvania), which filed for Chapter 11 bankruptcy protection for $31 million (MDD, June 12, 2008). It was previously approved for use with prostate and colorectal cancers.

The test works by using antibodies that are joined to microscopic iron particles, called ferrofluid. The antibody/ferrofluid combinations attach very specifically to CTCs. Powerful magnets then draw the CTCs out of the blood sample and they are then stained with additional biomolecules and chemicals to be identified as CTCs.

In the current retrospective study, published in the Journal of Clinical Oncology, investigators compared how well CTCs and a conventional modality, fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), predicted survival in MBC patients on standard therapies. Results showed that both technologies significantly correlated to overall metastatic breast cancer patient survival. But CTC could better predict the prognosis and survival of metastatic breast cancer patients.

"Every patient had CTC assessments before and after treatment and imaging. We saw that CTC performed as expected," Cristofanilli said. "But what was surprising was that CTC was superior to predict response to therapy. If you think about the cells, even the most sensitive imaging tests can miss differences at the biological level. We need to move from anatomical and functional assessments to a more biological way to measure and this was a more sensitive way."

The study included 115 patients with metastatic breast cancer. The CellSearch test was performed as part of their initial staging process at M.D. Anderson over a three-year period. CTC count and FDG-PET/CT imaging were performed at baseline in 102 evaluable patients before starting a new therapy and then again at the midpoint of their therapies. In the final analysis, both mid-therapy CTC counts and FDG-PET/CT response predicted overall patient survival. The results also suggested a higher and independent predictive value of CTCs compared with FDG-PET/CT among patients with a CTC count of five or more.

Cristofanilli said the CTC test is currently being used as an addendum to other diagnostic methods, but "this is another piece of information to suggest it's as good as imaging." He added that "this also suggests that, in the future, maybe we should try to look more specifically at real-time monitoring of CTC tests. We do so many imaging tests and this is a way, in the future, to lessen the number of imaging tests and the high costs."