Should Hematopoietic Stem Cell Transplantation in First Complete Remission Be Restricted to High-Risk Patients in Childhood Acute Myeloid Leukemia?.

Hematopoietic stem cell transplantation (HSCT) has been used as an effective consolidation therapy for children with acute myeloid leukemia (AML) in first complete remission (CR). Although it is effective in relapse prevention, often it causes severe late sequelae, such as short stature and infertility. There is a recent trend to restrict the use of HSCT in first CR for high-risk patients. However, there is no study comparing which strategy is better, risk-adapted or general recommendation for HSCT in AML children in first CR. In our institutes, all such children in first CR were recommended either allogeneic or autologous HSCT until 1997. After 1998, patients were classified into three risk-groups. Low-risk patients (t(8;21) and inv(16)) were not recommended to undergo HSCT. High-risk patients (−7, 5q-, Ph1, t(16;21) and remission failure) were recommended to undergo HSCT. Intermediate-risk (other karyotypes) patients received HSCT in first CR if a suitable donor was available. In this study, we retrospectively compared the prognosis of 66 patients who were diagnosed with de novo AML between 1991 and 1997 (group A; n=37) and between 1998 and 2003 (group B; n=29). AML with Down syndrome and AML-M3 were excluded. The median (range) age was five (0–15) years. FAB classifications were M0 (n = 1), M1 (n = 10), M2 (n = 22), M4 (n = 6), M4E (n = 5), M5 (n = 14), M6 (n = 0), and M7 (n = 8). Chromosome analysis data were t(8;21) (n = 18), inv(16) (n = 4), 11q23 (n = 10), other abnormalities (n = 14), normal karyotype (n = 14), and unknown (n = 6). Induction chemotherapy comprised VP-16, cytarabine, and mitoxantrone. Sixty-three of 66 patients (95.5%) achieved CR. HSCT in first CR was done in 24 patients (64.9%) in group A and seven patients (24.1%) in group B (p = 0.0044). Age, sex, WBC count at diagnosis, FAB classification and chromosomal abnormalities did not differ between the two groups. Fourteen (five in group A and nine in group B) patients relapsed. Six (three in group A and three in group B) of them were salvaged by HSCT. Both 5-year event-free survival (EFS) and overall survival (OS) were statistically higher in group A than in group B (5-year EFS: 83.8 ± 6.1% versus 62.1 ± 9.0%, p = 0.0404; 5-year OS: 91.6 ± 4.7% versus 71.6 ± 8.5%, p = 0.0364). Although intensified chemotherapy without HSCT for low-risk AML patients is desirable to avoid the late complications of HSCT, our analysis showed that the introduction of risk-stratified treatment strategy significantly worsened the chances of EFS and OS. Our risk stratification based on chromosomal abnormalities only may be insufficient to identify low-risk AML children. Development of more sophisticated risk classification, including molecular markers, may be required to identify true low-risk patients who should avoid HSCT in first CR.