High-dose cladribine therapy for chronic myelogenous leukemia in the accelerated or blast phase

A phase II clinical trial was performed to evaluate the effectiveness of high-dose cladribine (2CDA) for treatment of chronic myelogenous leukemia (CML) in the accelerated or blast phase.

Nineteen patients were treated. The median age was 55 years (range, 30 to 73). Six were older than 60 years. Eight had progressed after intensive combination chemotherapy and three after allogeneic or autologous transplantation. For the first course, 16 patients received 2CDA at 15 mg/m2/d intravenously (i.v.) over 1 hour for 5 days. Two received 18 mg/m2 and one received 21.5 mg/m2 daily. The second course was escalated to 20 mg/m2/d in five patients.

Rapid cytoreduction of leukemia occurred in the blood, with the nadir at 10 to 12 days. The median WBC count decreased from 36,900/microL before treatment to 500/microL at the nadir and recovered to 5,200/microL at day 30. The median platelet count changed from 113,000/microL to 24,000/microL at the nadir and 71,000/microL at day 30. The complete remission (CR) plus partial remission (PR) rate was 47% (95% confidence interval [CI], 23% to 72%). One 64-year-old man with lymphoid blast phase of CML had a morphologic and cytogenetic CR that lasted 9 months. The median survival for all patients was 34 weeks, and the median survival for the eight responders was 56 weeks (range, 11 to 167). The median number of days spent in hospital over the entire treatment period was 19 (range, 4 to 60).

High-dose 2CDA therapy provides effective palliation for CML in accelerated or blast phases, even for heavily pretreated patients.