Idarubicin in blastic crisis of chronic myelogenous leukemia

Blastic crisis (BC) is the terminal event in the natural history of most chronic myelogenous leukemia (CML) patients. Depletion of the normal stem cell compartment, as well as the proliferative advantage and frequent pharmacoresistance of the blastic clone, contribute to the poor prognosis of CML patients in this phase. Recent clinical trials have shown that idarubicin (IDR) in combination with cytosine arabinoside (ARA-C) is more active than daunorubicin at comparable doses in acute myelogenous leukemia (AML). Furthermore, IDR alone also exhibits antitumoral activity in the BC of CML.

Twelve Ph+ CML patients in BC (male 8, female 4; median age 45 yrs., range 19-55 yrs.) were treated with IDR 12 mg/m2/die for 3 consecutive days in sequential combination with Ara-C (1 hour i.v. infusion) 120 mg/m2/12 hrs. for 7 consecutive days. BC exhibited a myeloid phenotype in 9 and a lymphoid phenotype in 3 cases. Median duration of the previous chronic phase had been 36 months (range 6-180).

Clearing of peripheral and bone marrow blasts was achieved in all but one patient. Three other patients were classified as resistant because of blastic regrowth, and 3 died of infection during postchemotherapeutic aplasia. Two patients achieved complete remission (CR) and 3 partial remission (PR). The median duration of response was 11 months (range 6-32).

In BC of CML the IDR/Ara-C combination led to an encouraging rate of either partial or complete responses. The relatively long duration of unmaintained response was even more interesting, with the duration of PR approaching that of CR. These data suggest that IDR should be considered as one of the first-line drugs in the treatment of BC of CML.