Fluorescence in situ hybridization evaluation of minimal residual disease on stem-cell harvests

The usefulness of fluorescence in situ hybridization (FISH) analysis to detect minimal residual disease (MRD) in autologous bone marrow and peripheral blood stem-cell harvests has been tested in three patients with hematologic malignancies. Conventional cytogenetics and FISH were used to characterize the leukemic clones identifying the specific chromosomal abnormalities (monosomy 7 in a myelodysplastic patient and trisomy 8 in two acute myeloid leukemic patients). Such analysis was useful to monitor the MRD persistent after treating these patients with intensive chemotherapy. The myelodysplastic patient underwent eight peripheral blood-stem cell harvests in which FISH detected the persistence of monosomy 7 cells, precluding their use for autologous transplantation. This patient relapsed and died. In two acute myeloid leukemia patients who underwent an autologous marrow harvest, FISH did not show a significant proportion of trisomy 8 cells. Nevertheless, autologous transplantation was not performed, owing to an insufficient CD34 cell content in the harvests. One of these patients relapsed with the reappearance of trisomy 8 and died. The other patient, on the contrary, is alive in complete remission 3 years after the bone marrow harvest. The usefulness and applicability of MRD quantification in stem-cell harvests is discussed on the basis of the sensitivity of the methodology applied.