Efficacy of Imatinib Mesylate, a Specific Inhibitor of BCR/ABL Tyrosine Kinase, on Chronic Myeloid Leukemia in Blast Phase

BACKGROUND OBJECTIVE:Chronic myeloid leukemia (CML) in blast ph as e is refractory with a poor prognosis. This study was to evaluate efficacy of im atinib mesylate, a specific inhibitor of BCR/ABL tyrosine kinase, on CML in blas t phase. METHODS: Nineteen patients with CML in blast phase (imatinib treatment group) received induction of cytarabine-based standard chemotherapy for 2 cycle s, and 400 mg/d of imatinib mesylate for 4 weeks. Patients with no remission rec eived 600 mg/d of imatinib mesylate for another 8 weeks. Treatment of 600 mg/d o f imatinib mesylate was maintained if it showed effects after 8 weeks, otherwise it would be stopped.Twenty-two patients with CML in blast phase (historical co ntrol group) received inducement of cytarabine-based chemotherapy for 2 cycles, and other regimens of consolidation or continuous induction. RESULTS: Sixteen p atients of imatinib treatment group achieved no hematologic remission after indu ction. After treated with imatinib mesylate,6 of 16 (38%) achieved hematologic complete remission (CHR),and major cytogenetic response;2 of 16(13%) achieved h ematologic partial remission (PHR); 1 of 16 (6%) returned to chronic phase with minor cytogenetic response. Total hematologic response rate of imatinib treatme nt group was 57%; 1-year survival rate was 38%(6/16). Eighteen patients of hi storical control group achieved no hematologic remission after inducement. After treated with other regimens, 2 (11%) achieved CHR, and 1 (6%) achieved PHR. T otal hematologic response rate of historical control group was 17%; 1-year sur vival rate was 6%(1/18),significantly lower than that of imatinib treatment gro up(P 0.05). CONCLUSIONS: Imatinib mesylate may have anti-leukemic activity, an d prolong survival time of patients with CML in blast phase. But problems of tum or relapse, and drug resistance are still present.