[The prognostic significance of derivative chromosome 9 deletions in chronic myeloid leukemia].

OBJECTIVE: To study the incidence and prognostic significance of derivative chromosome 9 [der (9)] deletions in chronic myeloid leukemia (CMA). METHODS: Dual-color dual-fusion BCR-ABL probe and fluorescence in situ hybridization (FISH) were use to detect chromosome preparations from 48 randomly selected CML patients in blast crisis (CML-BC). If only one fusion signal was detected in interphase cells with FISH, metaphase cells were simultaneously observed to determine if there were deletions on der (9). Chromosome preparations made at diagnosis from those with der (9) deletions in CML-BC were also assayed to determine if der (9) deletions occurred at the time of Philadelphia translocation. Patients in chronic phase were treated with hydroxyurea. RESULTS: Of the 48 CML-BC cases, 8 (16.7%) showed der (9) deletions and the deletions also existed in chromosome preparations made at diagnosis. The group with der (9) deletions had significantly shorter duration of chronic phase and overall survival than the group without (P < 0.05). There was no difference in the probability of the der (9) deletions between the cases transformed to acute lymphoid leukemia and those to acute myeloid leukemia (P > 0.05). CONCLUSIONS: FISH technique can effectively detect der (9) deletions. Der (9) deletions occur at the time of Philadelphia translocation. CML patients with der (9) deletions have more rapid process and poor prognosis. Hydroxyurea could not reverse the poor prognosis of der (9) deletions in CML. Der (9) deletions might not lead to transformation to specific type in CML.