Analysis of sensitivity and specificity of cytokeratin 19 reverse transcriptase/polymerase chain reaction for detection of occult breast cancer in bone marrow and leukapheresis products

Abstract

Purpose: The work aimed to evaluate the sensitivity and specificity of the cytokeratin (CK) 19 reverse transcriptase/polymerase chain reaction (RT-PCR) for the detection of occult breast cancer in bone marrow and leukapheresis products. Materials and methods: Peripheral blood and bone marrow samples, obtained from 96 and 8 healthy donors respectively, served as negative controls. A total of 115 bone marrow samples and 29 leukapheresis samples from routine patients with breast cancer were analysed by CK19 RT-PCR. The PCR results were compared with those from routine immunocytology for CK8, 18, 19. Results: The CK19 RT-PCR technique with primer pairs from Datta et al. (J Clin Oncol 12: 475–482, 1994), using an annealing temperature of 72°C, allowed the detection of one tumour cell in 10⁷ mononuclear cells. None of the control samples (96 peripheral blood and 8 bone marrow) that were positive for β₂-microglobulin by RT-PCR showed a signal for CK19. However, expression of CK19 mRNA was observed in 40.87% (70/115) of bone marrow and in 24.13% (7/29) of leukapheresis samples of patients with breast cancer. Standard immunocytology and PCR were combined for the detection of tumour cells. Five of the 65 bone marrow samples were found to be positive by CK19 RT-PCR, but were negative with the immunocytology method. Conclusion: RT-PCR using CK19-specific primers and optimal experimental conditions is a reliable and specific method for the detection of micrometastatic breast cancer cells.