[Clinical significance of detecting circulating cancer cells in patients with solid malignancies]

There have been several studies attempting to detect the existence of cancer cells in the peripheral blood of patients with solid malignancies. The use of RT-PCR assays for cytokeratin (CK), carcinoembryonic antigen (CEA), alpha-fetoproteins (AFP), prostate specific antigen (PSA) and prostate specific membrane antigen (PMSA) is likely to be practicable in the detection of circulating tumor cells from epithelial-derived malignancies. The positive rates varied widely among the studies attempting to detect circulating cancer cells in peripheral blood, even when the same targets were used, which may be explained by the sensitivity of the RT-PCR assays and the target genes used. Both false negative results and false positive results can be obtained with the RT-PCR assay system. Furthermore, cancer cells may be released from the primary cancer into the circulation intermittently rather than constantly, and the results may vary among the samples obtained at different time points. In this report, we review our recent studies and related studies by other researchers to show the advances and the problems in detecting circulating cancer cells in patients with solid malignancies. The clinical significance of detecting circulating cancer cells in peripheral blood remains to be determined.