Trial results boost circulating tumor cell field.

Tumor cells that invade the bloodstream and reach distant organs are the seeds of death. " Patients with cancer … don't die from the primary tumor, they always die from metastases, " said Leon Terstappen, M.D., Ph.D., chief scientific officer of Immunicon, a Pennsylvania biotechnology company. Because tumor cells make their way to the site of distant metastases via the bloodstream, " there must be cells there, " Terstappen pointed out. In theory, finding such circulating tumor cells, or CTCs, could identify metastatic disease at its very earliest stage. But the technical hurdles for creating such a clinical test are enormous. " We're looking for really one cell, a weird cell, in a background of maybe 20 million cells, " said David Krag, M.D., professor of surgery at the University of Vermont. " Boy, that can be really tough. " But research into circulating tumor cells took a big leap forward in June. In a talk at the American Society of Clinical Oncology (ASCO) annual meeting, University of Michigan medical oncolo-gist Dan Hayes, M.D., reported prospective clinical trial results using a test developed by Immunicon to detect CTCs in patients with metastatic breast cancer. Of 177 cancer patients, nearly 50% had at least five CTCs in a 7.5-milliliter blood sample before chemotherapy treatment, and 30% of these patients still exceeded this five-CTC threshold at a follow-up exam 3 to 4 weeks later. (No patients with benign conditions had more than two CTCs in a blood sample at any time.) Patients with a high CTC count had a much worse prognosis, but Hayes' most striking data showed that CTC count was associated with treatment response: for patients with five or more CTCs at first followup, progression-free survival was 2.1 months, compared with 7.0 months for patients with fewer than five CTCs. " These data suggest that, for a patient who has an elevated CTC level