New Mulltiple Marker Blood Test Detects Melanoma Tumor Cells

Researchers at the John Wayne Cancer Institute at Saint John'sHospital in Los Angeles are studying a new blood test that usesfour genetic markers to detect melanoma cells in patients whohave no clinical signs of the disease. This multimarker "reversetranscriptase polymerase chain reaction" (RT-PCR) assay isbeing developed jointly by the John Wayne Cancer Institute andthe National Genetics Institute. Their data were presented atthe annual meeting of the American Society of Clinical Oncology.

"Conventional RT-PCR technology for melanoma uses a singlegenetic marker," explains Dr. Dave S. B. Hoon, head of JohnWayne's molecular immunology division, "but we've been ableto incorporate multiple markers for melanoma. This makes our assaymore sensitive for determining the extent and severity of disease."Dr. Hoon, along with Dr. Andrew Conrad of the National GeneticsInstitute, developed the multimarker assay, which can identifya single melanoma cell in more than 10 million blood cells.

Investigators at the John Wayne Institute are currently usingthe multimarker RT-PCR assay to determine the actual stage ofmelanoma in patients with clinically localized disease. It hasthus far been used to evaluate 119 melanoma patients. The MedicalDirector at John Wayne, Donald L. Morton, MD, says that thereis a significant correlation between the patient's stage/statusof disease and the number of markers detected. "We're findingthat a higher number of melanoma markers in a patient's bloodis associated with a poorer prognosis."

According to Dr. Hoon's associate, Dr. Paul Dale, "Laboratorydetection of metastatic cancer can be very difficult because cancercells are usually very heterogeneous. Different cancers expressdifferent markers, and even cells from the same tumor may notbe identical. We've basically developed an 'umbrella' assay thatcan detect almost all types of melanoma cells.