Veridex, LLC, a Johnson & Johnson company, has announced that the US Food and Drug Administration (FDA) has granted an expanded clearance for the CellSearch System to be used as an aid in the monitoring of metastatic colorectal cancer. CellSearch is currently approved for monitoring metastatic breast cancer.

The CellSearch System identifies and counts circulating tumour cells (CTCs) in a blood sample to predict progression-free survival and overall survival in patients with metastatic colorectal or breast cancer, and can do so earlier than the current standard of care. The results of serial testing for CTCs with the CellSearch System, in conjunction with other clinical methods for monitoring, can help physicians assess disease progression, thereby guiding more informed care decisions earlier.

"We are very excited that we can now offer the CellSearch test to patients who have metastatic colorectal cancer," said Dr. Ravi Patel, Comprehensive Blood and Cancer Centre in Bakersfield, California, which will become the first clinical site in the US to offer the test under the new indication. "CellSearch will have a very positive impact on the care of these patients, in the same way it has positively impacted the care of our patients with metastatic breast cancer over the last year."

The CellSearch System is the first diagnostic test to automate the detection and enumeration of CTCs, cancer cells that detach from solid tumours and enter the blood stream, and is the standard in a new class of diagnostic tools. 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.

According to the American Cancer Society, colorectal cancer claims approximately 55,000 lives each year, the vast majority of which are a result of recurrent metastatic disease. Metastatic colorectal cancer occurs when tumour cells spread to other locations in the body and grow. Although there are several options for the treatment of metastatic colorectal cancer, 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 through its ability to locate minute numbers of circulating tumour cells in the approximately 40 billion cells contained in a 7.5 ml sample of blood - an achievement never before documented in any diagnostic tool.

The CellSearch System was originally cleared by the FDA in January 2004 as a diagnostic tool for identifying and counting CTCs in a blood sample to predict progression-free survival and overall survival in patients with metastatic breast cancer.

A prospective, multi-centre clinical trial was conducted to validate the expanded clearance for CellSearch. The study, which took place in 55 clinical centres in the United States and Europe, involved 430 metastatic colorectal patients about to enter first- or second-line therapy. Data showed that patients with less than three CTCs at baseline had significantly better survival rates versus patients with more than three CTCs - an overall finding consistent with metastatic breast cancer patients. 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 radiological assessment may provide the most accurate assessment of prognosis.

"Clinical research validates the significance of circulating, cancer tumour cells," said Robert McCormack, Ph.D., vice president, Medical and Scientific Affairs, Veridex. "Elevated CTCs in the blood stream are associated with lower survival rates. We believe, based on the clinical research, that identifying CTCs as soon as possible can lead to improved patient outcomes."

The CellSearch test works by using 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. They are then stained with additional bio-molecules and chemicals so that they can be positively identified as CTCs. The CellSearch test differs from the current standard of care because it can be used much earlier than traditional imaging (e.g., CT scans), and is not subject to the variation observed with other blood tests, called serum tumour markers.

In August 2004, a clinical study using the CellSearch test in metastatic breast cancer patients was published in The New England Journal of Medicine. The authors of this study concluded "the very short median progression-free survival in patients with elevated circulating tumour cells at the first follow-up visit suggests that these patients are receiving ineffective therapy." In addition, as recently as November 2006, a metastatic breast cancer study was published in Clinical Cancer Research where the authors concluded: "The results reported here indicate that the evaluation of CTCs is an accurate measure of treatment efficacy." Additionally, the authors said: "The ability to serially quantitate and interrogate CTCs in patients with breast cancer makes possible new ways of managing and investigating the disease."

Veridex, LLC, a Johnson & Johnson company, develops cancer diagnostic products that will enable earlier disease detection as well as more accurate staging, monitoring and therapeutic selection. The company is initially developing two complementary product lines: CellSearch assays that identify, enumerate and characterize circulating tumour cells directly from whole blood; and GeneSearch assays that use molecular technology to diagnose, stage and more accurately characterize tumours.