5 mL with outcomes (8). The same cut off (2 CTCs) was used for bladder cancer where EpCAM detection is about

35% (8,25). The reasons why there is variability in detection rates compared to immunohistochemical expression of EpCAM are not entirely clear. The lack of the ability to detect CTCs in a higher percentage of patients with metastatic cancer may be due to the epithelial-mesenchymal transition (EMT), less expression of epithelial surface antigens (1) and there less EpCAM detection by CellSearch technology in advanced cancer (34). A recent study using the CellSearch system has shown that normal-like breast cancer subtype cell line with features of EMT has EpCAM levels that are too low to allow Inhibitors,research,lifescience,medical capture using their antibodies which raises the importance of developing alternative CTC markers Inhibitors,research,lifescience,medical in such specific circumstances (35). In colorectal cancer, in spite of EpCAM overexpression in almost 100% of cells on immunochemistry, detection can be as low as 25% where the cut off is set for 3 CTC/7.5 mL using CellSearch assay (8,26,29,36). Our inhibitors purchase results support that the same concept can be applied to biliary cancer as 25% of the patients had Inhibitors,research,lifescience,medical two or more CTCs/7.5 mL, when tumor EpCAM Expression ranges from 63-100% in cholangiocarcinoma and 81-90%

in gallbladder cancer. Some drawbacks of this study are the lack of control healthy donors to evaluate false positive results. However it is expected to be very low based on similar examples of published breast and colon cancer studies. As this was intended as a pilot study, there was also some heterogeneity in advanced cancer patients as some were not treatment naïve and some opted for supportive care during the followup period. As changes in CTCs in Inhibitors,research,lifescience,medical circulation can be a function of disease burden and response to therapy,

this limits a true assessment of the frequency Inhibitors,research,lifescience,medical of CTC detection at diagnosis in this illness. However this may not be a major drawback in the study design since positive CTCs correlated with poor outcome even at different intervals of the follow up in patients with metastatic breast cancer (8). Another drawback would be the source of the CTC in those patients, all patients underwent surgical or radiology guided biopsies of their initial tumors including all the liver masses outlined in Tables 1 and ​and33 which were all positive for their respective diagnosis nearly of either gallbladder cancer or cholangiocarcinoma. However, lung or bone involvements of disease were not required to be biopsy proven per standards of care as patients’ radiological staging was consistent with metastases from their pathology proven initial cholangiocarcinoma or gallbladder cancer without any evidence of the presence of other primary tumors in those patients. As a clinical observation, two patients had serial CTC values in their disease course.