Improvement of induction remission rate by modifying the dose of idarubicin for relapsed childhood acute lymphoblastic leukemia.

Relapse is the major cause of treatment failure in acute lymphoblastic leukemia (ALL), yet there is no established treatment for relapsed ALL. To improve the induction remission rate, we modified the dose of idarubicin in the original Children's Cancer Group (CCG)-1884 protocol, and retrospectively compared the results. Twenty-eight patients diagnosed with relapsed ALL received induction chemotherapy according to the CCG-1884 protocol. Complete remission (CR) rate in all patients after induction chemotherapy was 57%. The idarubicin 10 mg/m(2)/week group showed CR rate of 74%, compared with the 22% CR rate of the idarubicin 12.5 mg/m(2)/week group (p=0.010). Remission failure due to treatment-related mortality (TRM) was 44% and 5.2% in the idarubicin 12.5 mg/m(2)/week and 10 mg/m(2)/week groups, respectively (p=0.011). Overall survival (OS) and 4-yr event-free survival (EFS) were 12.8% and 10.3%, respectively. OS and 4-yr EFS were higher in the idarubicin 10 mg/m(2)/week group (19.3% and 15.6%) than in the 12.5 mg/m(2)/week group (0% and 0%). In conclusion, a modified dose of idarubicin from 12.5 mg/m(2)/week to 10 mg/m(2)/week resulted in an improved CR rate in the treatment of relapsed ALL, which was due to lower TRM. However, despite improved CR rate with modified dose of idarubicin, survival rates were unsatisfactory.