Detection of circulating tumor cells in venous blood of nasopharyngeal carcinoma patients by nested reverse transcriptase-polymerase chain reaction.

Nasopharyngeal carcinoma (NPC) is a radiosensitive tumor. Because of recent advances in radiation oncology, distant metastasis has become the predominant failure site after adequate radiotherapy. The purpose of this study is to establish a nested reverse transcriptase-polymerase chain reaction (RT-PCR) system and to evaluate the potential of cytokeratin 19 (CK-19) mRNA as a target for detecting micrometastasis in the blood of NPC patients. Venous blood samples from 40 patients with biopsy-proven NPC (25 previously untreated and 15 after radiotherapy) and 20 healthy volunteers were tested. We divided the 40 patients into 4 groups: cured, early stage, advanced stage, and metastasized, according to results of clinical staging work-up. Under our nested RT-PCR experimental conditions, 2 of 8 early stage patients (25.0%), 6 of 15 advanced stage patients (40%), and 6 of 8 patients with distant metastasis (75%) had CK-19 positive cells in peripheral blood (P = 0.11). No CK-19 positive cells were detected in 9 "cured" patients and 20 healthy volunteers. Our data indicated that the positive detection rate for CK-19 mRNA in peripheral blood increased as the clinical stage of disease increased, but the difference did not reach statistical significance. Longer follow-up is needed to assess the significance of CK-19 mRNA in blood, as well as its relation to subsequent metastasis and prognosis of NPC.