Background & objective: The aberrant regulation of the protein tyrosine kinase (PTK) activity of P210(BCR-ABL), which is the protein product of Bcr-Abl fusion gene leads to the pathogenesis of chronic myeloid leukemia (CML). Though STI571 can inhibit specifically the PTK activity of P210(Bcr-Abl) and greatly improve the clinic curative effect on CML in chronic phase, its effect on CML in accelerated phase and blast crisis is not clear. In this article, we attempted to analyze the clinic efficacy and side effect of STI571 treatment on CML patients in different phase. In addition, we analyzed the potential mechanism of STI571 resistance in accelerated/blast crisis CML with genetic methods.
Methods: A total of 22 cases of CML, 14 cases male and 8 female, 6 cases in chronic phase and 16 cases in accelerated/blast crisis phase, were treated with STI571. According to the efficacy standard, the hematological and cytogenetic response of 22 cases CML were analyzed, by determining the positive rate of Ph chromosome in bone marrow from the patients treated with STI571 for 3 months. Furthermore, the karyotype evolution of those patients showing STI571 resistance was analyzed. At the same time, the side effects and adverse events of STI571 treatment were evaluated.
Results: 6/6(100%) cases of CML patients in chronic phase acquired hematological CR and cytogenetic response. 4/16(25%) cases in accelerated phase or blast crisis acquired hematological CR and 8/16(50%) cases acquired cytogenetic response. 3 CML patients in blast crisis showed secondary STI571 resistance. The karyotype analysis shows 2 with 2 Ph chromosome and other additional abnormality. I/II grade non-hematological toxicity was observed in all the patients, including edema (77.3%), side effects of digestive system (36.4%) and myalgia (22.7%) et al. Severe hematological toxicities includes:(1)III/IV grade neutropenia (9 cases):1/6 cases of CML patients in chronic phase, 8/16 cases in accelerated phase or blast crisis; (2)III/IV grade thrombocytopenia (6 cases): 6/16 cases in accelerated phase or blast crisis. The percentage of III/IV grade neutropenia/thrombocytopenia in chronic phase and accelerated/blast crisis phase was compared and no significant statistical difference was observed.
Conclusions: Hematological and cytogenetic responses of different degrees can be acquired in CML-CP and CML-AP/BC patients treated with STI571 and showing statistic difference. STI571 improves the clinic curative effect greatly on CML in chronic phase. CML patients in blast crisis have secondary STI571 resistance with novel 2 Ph chromosome and other additional abnormality, it furnishes the evidence of the gene changes. The slightness of non-hematological toxicity of STI571 in the treatment of chronic myeloid leukemia suggests this drug is relatively safe. Severe hematological toxicities, such as III/IV neutropenia and thrombocytopenia, are more common in accelerated/blast crisis than in chronic phase.