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February 18, 2002 On the Trail of Tumor Cells Oncologists have long known that solid tumors slough off cells with surprising speed. The more aggressive the tumor, the more cells it sheds. And each cell has the potential to spawn a new tumor far away from the original site. Scientists at the closely held Immunicon Corp., based in Huntingdon Valley, Pa., think they can take advantage of this shedding process to provide an early warning on tumors. They have developed an exquisitely sensitive test that detects small numbers of tumor cells circulating in the bloodstream. First, blood cells are mixed with a suspension of tiny magnetic particles. The particles are armed with specialized tags that glom on to any cancer cells in the sample. When the sample is placed in a magnetic field, the cells bound to the particles are separated from the rest and can then be analyzed. In trials, the test proved sensitive enough to detect as few as 10 cells in a 7 milliliter vial of blood. The company is conducting clinical trials to see if the technology can be used to monitor how well breast-cancer patients respond to different therapies. If the cancer is under control, the number of tumor cells picked up by Immunicon's test is expected to decrease. Copyright 2002, by The McGraw-Hill Companies Inc. |