News FocusMedicine

Cancer's Circulation Problem

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Science  26 Feb 2010:
Vol. 327, Issue 5969, pp. 1072-1074
DOI: 10.1126/science.327.5969.1072

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Researchers are exploring a new window for tracking the spread of cancer: the vanishingly few tumor cells that circulate in a patient's blood. Clinical researchers are now counting these circulating tumor cells (CTCs) every few weeks in patients with several types of metastatic cancer, a crude but potentially useful measure for gauging whether a treatment is working. Researchers have also begun to analyze CTCs for certain gene variants or proteins that indicate a patient's tumor is susceptible to a particular drug. The growing ability to detect and analyze CTCs could also galvanize the development of drugs designed to block metastasis. Compared to waiting for secondary tumors to appear, monitoring CTC counts may give companies a shortcut for measuring whether an antimetastasis drug works. At the same time, CTC research faces hurdles. Any new CTC detection technology is considered a disease monitoring device by U.S. regulators and must be validated in clinical trials. And because CTCs are so rare and hard to capture, most separation strategies are thought to miss some of the cancer cells. Moreover, researchers don't yet have a good handle on whether the cells they're collecting from people's blood are the ones that can seed new tumors. Further analysis of CTCs could answer that question and confirm that the picture of metastasis developed over the past decade in animal studies is the same in people.