Objectives: To investigate the diurnal variations in circulating tumor cells (CTCs) in metastatic carcinoma of the prostate (CAP) and to determine whether the change in CTCs correlated with disease progression.
Methods: Samples were prepared by immunomagnetic selection of cells from 7 mL of blood targeting the epithelial cell adhesion molecule and differential fluorescent labeling of the collected cells using a nucleic acid dye, antibodies directed against the common leukocyte (CD45), and cytokeratin antigens. Events that stained with the nucleic acid dye and expressed cytokeratin but lacked CD45 were defined as CTCs by multiparameter flow cytometry.
Results: Male controls (n = 22) exhibited 0.8 +/- 1.2 events per 7 mL blood compared with 5.9 +/- 4.7 in 10 samples from patients with localized CAP and 46.6 +/- 65.6 events in 10 samples from patients with metastatic CAP. Diurnal testing of 8 cases demonstrated stable levels of CTCs. Ten patients were serially analyzed during a 6-month period for serum prostate-specific antigen and CTCs. The correlation between the prostate-specific antigen level and CTC number was fair. Slow disease progression was found in 4 patients with low CTC numbers (3.0 +/- 3) but it was significantly higher than the control group (P <0.002). Rapid disease progression occurred in 6 patients who demonstrated high CTC numbers (68.5 +/- 71.9). Two patients received chemotherapy that caused substantial fluctuations in the CTCs with less pronounced changes in the prostate-specific antigen level.
Conclusions: We conclude that the level of CTCs can be quantified in the circulation of patients with metastatic CAP and that the change in CTCs correlates with disease progression with no diurnal variations.