Detection of circulating tumor cells in the peripheral blood of patients with androgen-independent, advanced or metastatic prostate cancer.

To the Editor: The presence of circulating tumor cells (CTC) in the peripheral blood of cancer patients has attracted a great deal of attention among investigators. The clinical significance of CTC has probably best been established in breast cancer, where it has been shown that the detection of CTC in metastatic patients correlates with early clinical relapse and patient death [1]. Gene expression profiling of CTC has been extended to other metastatic cancers including colorectal and prostate cancer [2,3]. Recently, a porous barrier density-gradient centrifugation system was developed that allows for enrichment of CTC from peripheral blood [4]. When coupled with the use of specific genes for real-time reverse transcriptase (RT)polymerase chain reaction (PCR), the buoyant density separation approach