Comparison of two methods for enumerating circulating tumor cells in carcinoma patients

Background: Monitoring of circulating tumor cells (CTCs) in blood of carcinoma patients treated with novel compounds may be a measurement of treatment effectiveness. Before it can be used clinically, a reliably method is needed to enumerate CTCs. We compared two methods for CTC enumeration, Onko-Quick and the CellSearch system. Methods: We drew 22.5 ml of blood into three CellSave tubes from 15 healthy donors and 61 patients with metastatic carcinoma. After pooling, 15 ml was processed with OncoQuick and 7.5 ml with CellSearch. Results: With both methods no CTCs were found in healthy donors. At least one CTC was detected in 14 of 61 patients (23%) with OncoQuick and 33 of 61 patients (54%) with CellSearch (P < 0.0001). The number of CTCs detected was larger for CellSearch (mean 20 CTCs/7.5 ml of blood) than for OncoQuick (3 CTCs/7.5 ml; P < 0.0001). Conclusion: The CellSearch system is a more accurate and sensitive method to enumerate CTCs. Further studies are warranted to evaluate CTC enumeration by the CellSearch system as a monitoring tool for the evaluation of the efficacy of novel anticancer agents. (c) 2005 international Society for Analytical Cytology.