392) using Fisher exact test. Overall survival between the two groups was not statistically significant using Kaplan Meier curve (P=0.796). However this is a pilot study that was not designed to compare overall survivals between patients with negative and positive CTC. Discussion The CellSearch is the first automated, standardized, reproducible and FDA approved

test for use in advanced metastatic breast (1,10), colon (11,12) and prostate cancer (13,14). Patients with positive Inhibitors,research,lifescience,medical CTC at baseline were predicted to have shorter progression free survival (2.7 vs. 7.0 months, 4.5 vs. 7.9 months, 4.2 vs. 5.8 months for breast, colorectal and prostate cancers, respectively) and overall survival (10.9 vs. 21.9 months, 9.4 vs. 18.5 months and 11.5 vs. 21.7 months for breast, Inhibitors,research,lifescience,medical colorectal and prostate cancers, respectively) when compared with patients with negative CTC. The same assay has been investigated in other solid tumors including melanoma (18), urothelial cancer (15-17), pancreatic (20,21) and lung cancer (19). The concept of detecting CTC in biliary cancer was previously described but using a completely different technique based on carcinoembryonic antigen reverse transcriptase polymerase chain

reaction (CEA RT-PCR) but none described CTC detection with an immunomagnetic Inhibitors,research,lifescience,medical assay (27). The strengths of this study are the use of a validated CLIA approved CellSearch system from Veridex to detect and enumerate the CTCs in the peripheral blood and the first report of detecting Inhibitors,research,lifescience,medical these cells in patients with gallbladder cancer and cholangiocarcinoma due to high frequency of EpCAM over expression (63-100% and 81-90% respectively according to different find more authors) (23,28-30) where it is described to be overexpressed in breast cancer in 81-100% in most of the subtypes with few exceptions (29). Cytokeratins 7, 8, 18, 19 and 20 were immunohistochemically Inhibitors,research,lifescience,medical examined in intrahepatic cholangiocarcinoma

tissue samples and were found to be expressed in 97, 97, 77 and 71% of immunohistochemistry respectively. Relatively similar results were found in samples from gallbladder cancer (31). Similar pilot studies have been used to help define a positive value which differs for each tumor type. Selection of the cut off value for positive CTC is based on EpCAM expression, detection rates and prospective validation second of its prognostic significance by statistical analysis. Positive CTC values are defined differently in different cancers (3CTC/7.5 mL for colorectal cancer, 5CTC/7.5 mL for breast and prostate cancers) (8) which is related to the variation (32) or loss in the expression of EpCAM (33). The cut off for CTC has not yet been defined in biliary cancer and in this study we propose to set it at 2 CTC/7.5 mL. The measurement of one CTC/7.