DETECTION OF RARE CIRCULATING BREAST-CANCER CELLS BY FILTRATION CYTOMETRY AND IDENTIFICATION BY DNA CONTENT - SENSITIVITY IN AN EXPERIMENTAL-MODEL

Current methods of detecting micrometastases in breast cancer fail in a large proportion of patients. Therefore an improved method for detec tion of metastases in blood samples could be of great clinical interes t both for prognosis and selection of patients for adjuvant systemic t herapy. We have developed a new non-invasive method which associates i mmune-magnetic separation and filtration cytometry. The sensitivity of our procedure was evaluated in a model system using a mixture from a human breast cancer cell line (MCF-7) and a normal human blood sample. The identification of tumoral cells was achieved by measuring DNA con tent in comparison with standard cells. The lowest concentration of MC F-7 detected was 1 tumoral cell in 500 000 white blood cells. In addit ion, filtration cytometry provides a visual control of nuclei permitti ng the elimination of all doubtful cases and an automatic count of tum oral cells directly per mi of blood, which may be an independent predi ctor of early relapse. This new method may avoid unnecessary axillary lymph node dissection in patients with negative nones. Our procedure s eems suitable for the detection of rare circulating cells in routine l aboratory testing and could be used in other applications.