RT-PCR amplification of CK19 mRNA in the blood of breast cancer patients: correlation with established prognostic parameters

We optimized the assay for detection of cytokeratin 19 (CK19) mRNA by the r everse transcriptase-polymerase chain reaction (RT-PCR) in blood as an inde x of circulating tumor cells in breast cancer patients. The limit of detect ion of < 1 MCF7 tumor cells per 10(6) peripheral blood leukocytes (PBL) was achieved in mixing experiments. We did not detect CKl9 mRNA in control blo ods (0/30) or in the blood of patients with benign breast disease (0/15). I n blood samples from 109 patients with invasive breast cancer, CK19 mRNA wa s detected in 7/23 patients with node-negative disease, in 21/58 with node- positive disease, and in 20/28 with distant metastases. There was a signifi cant association (P < 0.01) of CK19 positivity with distant metastatic vers us both node-negative and node-positive disease, but not with any other his topathological parameter examined. In a small number of patients with dista nt metastases, increased intensity of the CK19 RT-PCR signal was associated with a reduced survival.