Cancer cells can enter the bloodstream, form distant metastases, and ultimately lead to death. A study by Allard and colleagues, which was published in the October 15, 2004, issue of Clinical Cancer Research, concluded that the Cell Search system could be used as a reliable tool to investigate circulating tumor cells and their clinical utility, and it spurred a stil-lgrowing interest in the field. (C) 2015 AACR.