This observation merits further validation as both baseline and early change in CTCs may prove to be useful to guide therapeutic decisions and to predict clinical outcomes. Conclusions This is the first report to show a clinical observation of detectable CTCs in patients with cancers of biliary origin. In this pilot study using a cutoff Inhibitors,research,lifescience,medical of 2CTCs/7.5 mL, 25% of patients with biliary cancer had detectable CTCs. Our results suggest that positive as well as negative CTC results may have prognostic value in predicting outcomes but need prospective validation. Our group is currently conducting a prospective study to determine the value of baseline

and change in CTCs during chemotherapy. This trial may help define the optimal CTC cutoff in predicting clinical outcomes in advanced biliary cancer patients. Funding Dr. Iyer

is supported by a grant from the American Inhibitors,research,lifescience,medical Cancer Society (MSRG -08-096-01-CCE). This research was supported, in part, by the National Cancer Institute (NCI) Support Grant to the Roswell Park Cancer Institute [P30 "type":"entrez-nucleotide","attrs":"text":"CA016056","term_id":"24293400","term_text":"CA016056"CA016056]. Footnotes No potential conflict of interest.
Since the first report in the 19th century, there have been numerous reports on the isolation and characterization of circulating Inhibitors,research,lifescience,medical tumor cells (CTCs) in peripheral blood in patients with various cancers (1-3). Recent studies have shown that the malignant Inhibitors,research,lifescience,medical characteristics of CTCs are genetically similar to the primary tumor (4,5). However, their characterization is of considerable biomedical interest in order to understand how these cells

can travel via the blood stream to anatomically distant sites and form metastatic disease. There have been many investigations which showed the utility of CTCs in the peripheral blood as a valuable Inhibitors,research,lifescience,medical diagnostic tool or a predictor of the clinical outcome in patients with solid tumors (2,3). In general, CTCs have been observed in the peripheral blood of cancer patients at very low concentrations of 10-7-10-8 of normal peripheral blood cells (6,7). Therefore, the detection of CTCs in blood requires highly sensitive, specific, and reproducible methods. To date, several methods including immunocytochemistry, reverse-transcription polymerase chain reaction (RT-PCR) or PCR procedures, and flow cytometry have been used for the detection of these rare CTCs no in the peripheral blood (2,3,7,8). Moreover the CTC-detection systems using the PS-341 mouse immunobead-based assays during the past ten years were designed to detect tumor cells in blood (9). By use of these systems, it is possible to obtain highly reproducible quantitative results. In particular, recently developed CellSearch System (Veridex LLC, Raritan, NJ) was designed to quantify the tumor cells in whole blood (9).