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

The usefulness of fluorescence in situ hybridization (FISH) analysis to det ect minimal residual disease (MRD) in autologous bone marrow and peripheral blood stem-cell harvests has been tested in three patients with hematologi c malignancies. Conventional cytogenetics and FISH were used to characteriz e the leukemic clones identifying the specific chromosomal abnormalities (m onosomy 7 in a myelodysplastic patient and trisomy 8 in two acute myeloid l eukemic patients). Such analysis was useful to monitor the MRD persistent a fter treating these patients with intensive chemotherapy. The myelodysplast ic patient underwent eight peripheral blood-stem cell harvests in which FIS H detected the persistence of monosomy 7 cells, precluding their use for au tologous transplantation. This patient relapsed and died. In two acute myel oid leukemia patients who underwent an autologous marrow harvest, FISH did not show a significant proportion of trisomy 8 cells. Nevertheless, autolog ous transplantation was not performed, owing to an insufficient CD34 cell c ontent in the harvests. One of these patients relapsed with the reappearanc e of trisomy 8 and died. The other patient, on the contrary, is alive in co mplete remission 3 years after the bone marrow han est. The usefulness and applicability of MRD quantification in stem-cell harvests is discussed on t he basis of the sensitivity of the methodology applied.