Detection of Disseminated Urothelial Cancer Cells in Peripheral Venous Blood by a Cytokeratin 20‐specific Nested Reverse Transcriptase‐Polymerase Chain Reaction

More than half of all patients with invasive urothelial cancer subsequently develop metastatic disease even after radical resection of the primary cancer. In these patients, neoplastic cells may be disseminated prior to or during the operation. A nested reverse transcriptase‐polymerase chain reaction (nested RT‐PCR) assay which amplifies cytokeratin (CK) 20 transcripts was used to detect cancer cells in the peripheral blood of urothelial cancer patients. This assay was able to detect 10 bladder cancer cell line cells in a sample of ten million peripheral‐blood mononuclear (PBMN) cells. CK 20‐specific signals were detected in 9 (22.5%) of 40 PBMN cell samples prepared from 40 urothelial cancer patients in relation to the tumor stage, including 0/13 patients with a superficial tumor, 4/21 (19%) with a regionally invasive tumor and 5/6 (83%) with a metastatic tumor (P=0.0002 in χ(2) test). No signals were detected in any of 25 healthy donor PBMN cell samples. The present results indicate that the CK 20 RT‐PCR assay is applicable for detection of urothelial cancer cells in the peripheral blood. The assay also confirms that hematogenic dissemination occurs in invasive urothelial cancers but rarely in superficial ones.