Interphase FISH for follow-up of Philadelphia chromosome-positive chronic myeloid leukemia treatment.

BACKGROUND Several attempts have been made to determine whether interphase fluorescence in situ hybridization (I-FISH) on bone marrow or peripheral blood specimens is a good alternative to conventional cytogenetics (CC) in calculating the residual proportion of Philadelphia (Ph) chromosome-positive cells during treatment follow-up of patients with chronic myeloid leukemia. MATERIALS AND METHODS Nineteen patients were selected for I-FISH follow-up compared to CC. All samples were also classified into 4 groups according to the percentage of residual Ph chromosome-positive metaphases analyzed in CC. I-FISH was performed using the LSI bcr/abl dual ES color probe (Vysis). RESULTS A high correlation was observed between the frequency of Ph chromosome-positive cells, assessed by CC and I-FISH (p<0.001). A high correlation was found between CC and I-FISH for 12 patients, but not for the remaining 7. Applying the same classification for I-FISH did not show a good relationship between the two techniques (p<0.001). CONCLUSION Dual color I-FISH is a reliable method to monitor the size of the Ph chromosome-positive clone in bone marrow of treated CML patients. However, it has to be complementary to conventional cytogenetics because it cannot detect the emergence of other chromosomal abnormalities in Ph chromosome-positive or -negative cells.