Improvement of breast cancer cell detection by immunomagnetic enrichment

Background Contaminating breast cancer cells in leukapheresis harvested for reinfusion to rebuild hemopoiesis after high-dose therapy have been descri bed by several investigators. Methods for tumor cell detection are conventi onal immunocytochemistry, culture techniques and reverse transcriptase PCR. The percentage of tumor cell positive leukaphereses shows a wide variation . An approach to clarify if these cells can induce systemic relapse is to c haracterize them molecular-genetically and immunologically, but these techn iques require a sufficient cell count. Methods We compared conventional immunocytochemistry after immunomagnetic e nrichment of cancer cells by HEA-125 magnetic microbeads for the detection of micrometastatic tumor cells. A total of 25 samples consisting of 16 samp les from G-CSF-mobilized peripheral stem cell harvests, eight BM aspiration s and one peripheral blood sample were investigated without [median 2, rang e 1-3 x 10(6) MNCs] and after [median 5, range 1-10 x 10(7) MNCs] HEA-micro bead selection. Additionally 10 buffy soar samples from healthy subjects we re investigated Results Using conventional immunocytochemistry, tumor cells could be detect ed in mine stem cell samples. Two BM samples ann the blood sample (48%) wer e positive, with a median tumor cell load of 0 (0-12) cells per sample (mea n: 2.4). By HEA-bead selection the rate of positivity could be increased to 88% (13 stem cell samples, eight marrow, samples and one blood sample) wit h a median load of 6 (0-47) (mean 10.6) suspected cells (p < 0.007). Howeve r; calculation of recovery revealed tumor cell losses by immunobead selecti on. False positive results were not seen. Discussion We conclude first that immunomagnetic selection is an excellent and highly sensitive tool to enrich contaminating cancel cells from marrow and stem cell samples; second that the existence of real tumor. cell negati ve stem cell harvests is doubtful and third that immunobead selection deliv ers sufficient tumor cell counts for their further characterization by mole cular and immunological methods.