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.