FLUORESCENCE IN-SITU HYBRIDIZATION (FISH) FOR EVALUATING RESIDUAL DISEASE IN PHILADELPHIA-CHROMOSOME-POSITIVE CHRONIC MYELOID-LEUKEMIA DURING INTERFERON-ALPHA THERAPY

Fluorescence in situ hybridization (FISH) is a quantitative technique which allows, by means of specific probes, to detect the t(9;22) trans location typical of chronic myeloid leukemia (CML) hematopoietic cells . We have evaluated FISH on interphase nuclei as a method for assessme nt of residual disease in bone marrow samples from 5 Philadelphia chro mosome positive (Ph(+)) CML patients after 12 months therapy with inte rferon alpha; results were compared with findings obtained by conventi onal cytogenetics and by polymerase chain reaction (PCR). Our data ind icate that FISH is more sensitive than cytogenetics for evaluation of residual disease, being positive in 1 out of 2 cases scored as Ph nega tive by cytogenetics, but is less sensitive than PCR which turned out to be positive in all patients. As additional advantage over conventio nal cytogenetics, FISH on interphase nuclei can be performed also on s amples lacking metaphases or having poor chromosome spreading or unsat isfactory chromosome banding.