Detection of circulating tumor cells in breast cancer patients utilizing multiparameter flow cytometry and assessment of the prognosis of patients in different CTCs levels.

We wanted to demonstrate the value of multiparameter flow cytometry in detecting human tumor cells of breast cancer (BC) (SKBR-3) in normal peripheral blood. In addition, we investigated a cluster of patients to compare the overall survival (OS) between advanced BC patients [circulating tumor cells (CTCs) >or=5 group] and limited BC patients (CTCs <5 group). SKBR-3 human BC cells were serially diluted in normal whole blood to demonstrate the sensitivity of multiparameter flow cytometry for detecting CTCs, and we also compared the specificity with reverse transcriptase polymerase chain reaction (RT-PCR) method. On the other hand, we detected CTCs among 45 patients by multiparameter flow cytometry. OS was calculated by the Kaplan-Meier product limit method, and compared it between CTCs <5 and CTCs >or=5 groups with the log-rank test. Cox regression models were fitted to determine the associated factors on survival. Human BC cells (SKBR-3) could be differentiated from normal blood based on the multiple light scatter and cell surface marker expression by multiparameter flow cytometry. The method was found to have a sensitivity limit of 10(-5) and was effective for detecting human BC cells in vivo. It also found that this method had a higher specificity compared with RT-PCR. For the retrospective study, the median OS was 95 weeks and 65.5 weeks (P < 0.05, 2-tailed) for patients with CTCs <5 and CTCs >or=5, respectively. Kaplan-Meier was used to analyze the patients' survival with Log Rank P = 0.004 and Breslow P = 0.003, which showed that these two groups had statistically significant difference. Cox regression analysis was performed, and we found CTCslevels, metastasis and age (P < 0.05) were three relative factors for patients' survival. Multiparameter flow cytometry can detect CTCs effectively and has the potential to be a valuable tool for prognosis assessment among BC patients in clinical situations in China.