Immunomagnetic quantification of circulating tumor cells in patients with urothelial cancer

Objectives: To evaluate the relationship between circulating tumor cells (CTC) and clinical parameters in metastatic urothelial cancer (UC). Methods: CTC were enumerated with the CellSearch System, which was developed using an EpCAM antibody-based immunomagnetic capture and automated staining methodology. UC cell lines (RT4, T24, TCC, UMUC3 and 253J) and mixed blood from healthy males were analyzed. Blood samples from 16 patients without metastatic UC and 20 patients with metastatic UC were also analyzed. Results: The accuracy and reliability of the assay were determined using spiked UC cells (RT4 and T24), which showed a strong linear correlation (r = 0.99) and recovery rate of 94% +/- 5% and 84% +/- 6%, respectively. Three UC cell lines (TCC, UMUC3 and 253J) tested negative. The 16 patients without metastatic UC tested negative as well. Eleven (55%) patients with metastatic UC tested positive for at least one CTC. Seven (35%) had two or more CTC. Significantly more CTC were seen in patients with two or more sites of metastasis than those with one site of metastasis (P = 0.004). Conclusions: Based on these findings, CTC could represent a potential marker to monitor the response to chemotherapy in patients with metastatic UC.