OBJECTIVEAcute promyelocytic leukemia (APL) is a specific type of hematopoietic malignancy, accounting for 10% of the de novo acute myeloid leukemia (AML). The data on long-term outcome of APL in children are limited. The aim of this study was to investigate the clinical biological features, diagnosis, prognosis and long-term survival of childhood APL.

METHODSA total of 46 children with newly diagnosed APL from April 1998 to October 2005 were enrolled into this study. Induction treatment containing all-trans retinoic acid (ATRA) plus daunorubicin (DNR) or pirarubicin (THP) was performed on these patients, followed by 6 courses of chemotherapy consolidation: DNR, homoharringtonine or etoposide plus Ara-C. A maintenance therapy was then administered once 3-6 months. The total period of treatment was 2.5 years.

RESULTSOf the 39 patients who had completed the regular treatment, 36 (92.3%) achieved a complete remission. The 5-year cumulative incidence of relapse (CIR) was 28.6%. The estimated overall survival (OS) rates at 1, 3 and 5 years were (86.1 +/- 5.8)%, (76.1 +/- 7.5)% and (70.2 +/- 8.9)% respectively, while the event free survival (EFS) rates were (78.4 +/- 6.8)%, (63.6 +/- 8.7)% and (53.1 +/- 10.0)% respectively. The 5-year OS rate of patients with WBC less than or equal to 10.0 X 10(9)/L was (81.4 +/- 10.3)%, which was significantly higher than that with WBC greater than 10.0 X 10(9)/L[(51.6 +/- 14.7)%, P < 0.05]. Five patients with RT-PCR positive for PML/RARalpha S (short) subtype died eventually although all of them achieved CR, but none of the 13 patients with PML/RARalpha L (long) subtype died.

CONCLUSIONSRemission induction therapy with ATRA + DNR or THP is effective and safe for newly diagnosed childhood APL. The remission induction therapy combined with chemotherapy containing high/intermediate dose Ara-C can improve the long-term survival rates of APL patients. High WBC count and S subtype of PML-RARa are two poor prognostic factors for children with APL.