Evaluation of breast tumour cell contamination in the bone marrow and leukapheresis collections by RT-PCR for cytokeratin-19 mRNA

There is considerable interest in an autologous transplantation (AT) progra mme for patients with high-risk breast cancer; however, the issue of the in cidence of occult bone marrow (BM) micrometastasis at diagnosis, and the ca ncer contamination of peripheral blood stem cell (PBSC) collections used fo r haematological rescue, is still debated. The presence of BM micrometastas is was evaluated in bilateral BM biopsies obtained at diagnosis of 33 patie nts with stage II/IIIA breast cancer using: (i) a 'nested' reverse transcri ptase-polymerase chain reaction (RT-PCR) assay for cytokeratin 19 (K19) mRN A, (ii) histology, and (iii) immunohistochemistry (IHC) analysis with a pan el of three monoclonal antibodies. The RT-PCR assay only was used to determ ine contamination of PBSC collections obtained after priming with recombina nt human granulocyte-colony stimulating factor (rhG-CSF). K19 transcripts i n one or both BM samples were detected in 48% of patients at diagnosis, wit h an overall 85% concordance with the results of IHC analysis. On the other hand, 56% of PCR- and IHC-positive BM samples were diagnosed as 'normal' o n histological analysis. 57% of patients showed K19 mRNA in at least one PB SC collection; the possibility to hare contaminated PBSC collections was si gnificantly higher in patients with K19 positivity in BM at diagnosis. In f our patients who had shown K19 positivity in BM and in PBSC collections, im munoselected CD34(+) cells used for haematological rescue were K19-negative . There was a trend towards longer relapse free survival (RFS) in patients transplanted with K19-negative PBSC collections as compared to the others. In conclusion, a substantial proportion of patients with high-risk non-meta static breast cancer present occult BM micrometastasis at diagnosis and als o show cancer contamination of PBSC collections used for AT. These might re present a category of patients with poorer prognosis after AT, and possible candidates for more intensive and/or alternative therapeutic regimens, inc luding AT with purged PBSCs.