Using a laser to identify cancerous cells, the scientists found that patients with breast and prostate cancer had significantly more epithelial cancer cells in their blood than people who are disease free, said Dr. Jonathan Uhr, professor of microbiology and internal medicine and lead author of the study in today's issue of Proceedings of the National Academy of Sciences. The investigators reported the test is more sensitive than currently available screening tests.
"The major potential use of this test would be to detect early tumors," said Uhr, holder of the Raymond Willie and Ellen Willie Distinguished Chair in Cancer Research, in Honor of Laverne and Raymond Willie Sr. "It's an extremely sensitive test. It can detect one cancerous epithelial cell in a milliliter of blood."
To identify the cells in the blood of cancer patients, the investigators treated blood samples with an antibody-coated iron particle to search for the cancer cells and then used a laser to turn malignant cells a different color than the rest of the sample. This allowed researchers to pick out cells with tumor characteristics. They confirmed findings by microscopic examination.
"Our major goal now is to fine-tune and automate the test before using it in high-risk patient groups to determine if we can pick up shedding of malignant cells from the primary tumor at a very early stage?possibly before detection of the primary tumor in some patients," Uhr said.
The scientists also showed that in all 12 breast-cancer patients in the study there was a positive correlation between the number of tumor cells in the blood and the clinical status: When the tumor was growing, the level of cancer cells in the blood was high. When they were effectively treated with chemotherapy, the cells disappeared. When relapse occurred, the count escalated again.
Comparing patients with malignancies found only in one organ with those whose lymph nodes were invaded by the disease and with patients whose cancer had spread to distant parts of the body, the researchers found a significant difference in the number of cancerous epithelial cells. The more advanced and invasive the disease, the greater the number of cancerous cells in the blood.
"One advantage of this method is that we can count the number of tumor cells in the blood, and it appears to be correlated in general with the extent of the tumor clinically," Uhr said. "Therefore, this test might also be useful to clinicians to monitor treatment.
"The prognostic significance of this test is that by counting the cells and characterizing them, it may be possible to predict the progressive states of the disease," he said. "But it will take many more patients and many years of research to find out if this method will work in that way and if it will be true for cancers other than breast and prostate."
The other researchers involved in the study were: Dr. Emilian Racila, assistant instructor of microbiology at the Cancer Immunobiology Center; Dr. David Euhus, assistant professor of surgical oncology; Dr. John McConnell, chairman of urology, holder of the E.E. Fogelson and Greer Garson Fogelson Distinguished Chair in Urology and director of the Dr. Bob Smith Foundation Center for Prostate Research, the George M. O'Brien Urologic Research Center and the Prostate Disease Center; Dr. Arthur Weiss of Jefferson Medical College of Thomas Jefferson University, Philadelphia; Dr. Chandra Rao and Dr. Leon Terstappen of Immunicon Corp.
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Journal
Proceedings of the National Academy of Sciences