Risk stratification and early intensification with high-dose cytarabine improves EFS for infants with KMT2A-rearranged ALL.
Early MRD clearance is a strong predictor of favorable outcome in infants with ALL.
The prognosis of infants with acute lymphoblastic leukemia (ALL), particularly those with KMT2A gene rearrangement (KMT2A-r), is dismal. Continuous efforts have been made in Japan to investigate the role of stem cell transplantation (HSCT) for infants with KMT2A-r ALL, but improvement in outcomes was modest. In the Japanese Pediatric Leukemia/Lymphoma Study Group trial MLL-10 (registered at umin.ac.jp as UMIN000004801), infants with ALL were stratified into three risk groups (low-risk, LR; intermediate-risk, IR; high-risk, HR) according to KMT2A status, age, and presence of central nervous system leukemia. A modified Children's Oncology Group AALL0631 chemotherapy with addition of high-dose cytarabine in early intensification was introduced to KMT2A-r patients, and the option of HSCT was restricted to HR patients. The role of minimal residual disease (MRD) was also evaluated. Ninety eligible infants were stratified into LR (N=15), IR (N=19), or HR (N=56). The 3-year event-free survival (EFS) rate (standard error) for patients with KMT2A-r ALL (IR+HR) was 66.2% (5.6%) and 93.3% (6.4%) for those with KMT2A-g ALL (LR). The 3-year EFS rate was 94.4% (5.4%) for IR and 56.6% (6.8%) for HR patients. In multivariable analysis, female sex and MRD ≧0.01% at end of early consolidation were significant poor prognostic factors. Risk stratification and introduction of intensive chemotherapy in the current study were effective and able to eliminate HSCT for a subset of infants with KMT2A-r ALL. Early clearance of MRD seems to have translated into favorable outcomes and should be incorporated into risk stratifications in future trials.