DETECTION OF RESIDUAL LEUKEMIC-CELLS IN PATIENTS WITH ACUTE PROMYELOCYTIC LEUKEMIA BY THE FLUORESCENCE IN-SITU HYBRIDIZATION METHOD - POTENTIAL FOR PREDICTING RELAPSE

The translocation between chromosomes 15 and 17, t(15;17)(q22-24;q11-2 1), is present in the bone marrow cells of most patients with acute pr omyelocytic leukemia (APL). Although conventional cytogenetic methods are useful for diagnosing this disease, difficulties are experienced i n detecting residual disease among those patients who have achieved re mission. In this study, we used the fluorescence in situ hybridization (FISH) method to attempt to detect residual leukemic cells in 10 APL patients in clinical remission. The duration of remission ranged from 2 to 93 months at the time of study. Multiple bone marrow samples were analyzed by FISH in most patients. In 6 patients, no cell with t(15;1 7) was found. These patients remain in complete remission at present ( approximately 25 to 33 months since first studied by FISH). In 4 patie nts, low frequencies of cells with t(15;17) were observed in at least one bone marrow sample examined. All of these patients relapsed within 1 to 14 months. No cell with t(15;17) was identified by the conventio nal G-banding method in any sample. The FISH results correlated well w ith that of a two-round nested reverse transcription polymerase chain reaction assay that was performed on the same samples. Thus, our study suggests that FISH is potentially a useful tool for detecting residua l APL cells and for identifying patients at high risk of relapse. (C) 1995 by The American Society of Hematology.