Preserved High Probability of Overall Survival with Significant Reduction of Chemotherapy for Myeloid Leukemia in Down Syndrome: A Nationwide Prospective Study in Japan

Background: On the basis of results of previous Japanese trials for myeloid leukemia in Down syndrome (ML-DS), the efficacy of risk-oriented therapy was evaluated in the Japanese Pediatric Leukemia/Lymphoma Study Group AML-D05 study. Procedure: All patients received induction chemotherapy that consisted of pirarubicin, intermediate-dose cytarabine, and etoposide. Patients who achieved complete remission (CR) after initial induction therapy were stratified to the standard risk (SR) group and received four courses of reduced-dose intensification therapy. Patients who did not achieve CR were stratified to the high risk (HR) group and received intensified therapy that consisted of continuous or high-dose cytarabine. Results: A total of 72 patients were eligible and evaluated. One patient died of sepsis during initial induction therapy. Sixty-nine patients were stratified to SR and two patients to HR. No therapy-related deaths were observed during intensification therapy. The 3-year event-free and overall survival rates were 83.3% ± 4.4% and 87.5% ± 3.9 %, respectively. Age at diagnosis less than 2 years was a significant favorable prognostic factor for risk of relapse (P = 0.009). Conclusions: The attempt of risk-oriented prospective study for ML-DS was unsuccessful, but despite the dose reduction of chemotherapeutic agents, the overall outcome was good, and further dose reduction might be possible for specific subgroups.