Metastatic Prostate Cancer Patients Monitored by CTCs

A diagnostic test automates the detection and enumeration of circulating tumor cells (CTCs), cancer cells that detach from solid tumors and enter the blood stream. The system's specificity, sensitivity, and reproducibility allow for serial assessment of CTCs as early as the first cycle of treatment to help evaluate disease progression sooner.

The test uses antibodies that are joined to microscopic iron particles, called ferrofluid. These antibody/ferrofluid combinations attach very specifically to CTCs. Powerful magnets then "pull” the CTCs out of the blood sample, and they are then stained with additional biomolecules and chemicals so that they can be positively identified as CTCs.

Called the CellSearch system, the test was developed by Veridex LLC (Warren, NJ, USA), a Johnson and Johnson company. The system has been approved by the U.S. Food and Drug Administration (FDA; Rockville, MD, USA) as an aid in the monitoring of metastatic prostate cancer (MPC) patients. The system is currently used for breast cancer and colorectal cancer patients to predict progression-free survival and overall survival in patients. The results of serial testing for CTCs with the CellSearch system provide additional information to the oncologist earlier than other currently approved diagnostic modalities, thereby allowing the oncologist to make more-informed patient care decisions.

According to the American Cancer Society, prostate cancer claims approximately 27,000 lives each year, the vast majority of which are a result of recurrent metastatic disease. Currently, oncologists often have to wait several months before they can determine if a specific treatment is beneficial to the patient. The CellSearch system helps physicians to predict disease progression and patient survival any time during therapy.

A prospective, multi-center clinical trial was conducted to validate the expanded clearance for CellSearch. The study, which took place in 65 clinical centers in the United States and Europe, involved 231 metastatic prostate cancer patients about to enter first- or later-line chemotherapy. Data showed that patients with less than five CTCs at baseline had significantly better survival rates versus patients with more than five CTCs. Data also showed that CTCs are a strong independent predictor of progression-free survival and overall survival, and that the combination of CTC analysis and prostate-specific antigen (PSA) assessment may provide the most accurate assessment of prognosis.

Dr. Nick Vogelzang, from the Nevada Cancer Institute (Las Vegas, NV, USA), said, "We have compared CellSearch CTC test results to the standard clinical and biomedical parameters, such as prostate specific antigen [PSA] measured in MPC [metastatic prostate cancer] patients. A decrease in the number of CTCs is most often associated with patients successfully responding to therapy. Further analysis of CTCs may provide information as to the most efficacious treatments for specific individuals.


Related Links:
Veridex
U.S. Food and Drug Administration
Nevada Cancer Institute