Researchers at the John Wayne Cancer Institute at Saint John's Hospital in Los Angeles are studying a new blood test that uses four genetic markers to detect melanoma cells in patients who have no clinical signs of the disease. This multimarker "reverse transcriptase polymerase chain reaction" (RT-PCR) assay is being developed jointly by the John Wayne Cancer Institute and the National Genetics Institute. Their data were presented at the annual meeting of the American Society of Clinical Oncology.
"Conventional RT-PCR technology for melanoma uses a single genetic marker," explains Dr. Dave S. B. Hoon, head of John Wayne's molecular immunology division, "but we've been able to incorporate multiple markers for melanoma. This makes our assay more sensitive for determining the extent and severity of disease." Dr. Hoon, along with Dr. Andrew Conrad of the National Genetics Institute, developed the multimarker assay, which can identify a single melanoma cell in more than 10 million blood cells.
Investigators at the John Wayne Institute are currently using the multimarker RT-PCR assay to determine the actual stage of melanoma in patients with clinically localized disease. It has thus far been used to evaluate 119 melanoma patients. The Medical Director at John Wayne, Donald L. Morton, MD, says that there is a significant correlation between the patient's stage/status of disease and the number of markers detected. "We're finding that a higher number of melanoma markers in a patient's blood is associated with a poorer prognosis."
According to Dr. Hoon's associate, Dr. Paul Dale, "Laboratory detection of metastatic cancer can be very difficult because cancer cells are usually very heterogeneous. Different cancers express different markers, and even cells from the same tumor may not be identical. We've basically developed an 'umbrella' assay that can detect almost all types of melanoma cells.
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