Comparison of Molecular Cytokeratin 19 Reverse Transcriptase Polymerase Chain Reaction (CK19 RT-PCR) and Immunocytochemical Detection of Micrometastatic Breast Cancer Cells in Hematopoietic Harvests

ABSTRACT Detection of small numbers of breast cancer cells in patient blood, aphereses, and bone marrow has become increasingly important as data have accumulated showing immunocytochemically (ICC) positive tumor cells in up to 50% of women with stage I and II breast cancer, who were initially thought to be cured of their disease but later relapsed. The ability to rule out the presence of micrometastatic disease at any stage of the clinical management protocol, whether before, during, or after therapy, would provide a useful monitoring and diagnostic tool for both the clinician and the scientist. Monitoring for the presence of minimal residual disease (MRD) is traditionally performed using ICC. A more recently established RT-PCR technique uses a molecular marker (the presence of the cytokeratin 19, CK19, transcript) to identify MRD in patient samples, with a level of sensitivity reported to be one tumor cell in 106 nucleated cells. This level of sensitivity is generally higher than that claimed for ICC. B...