In childhood B-ALL, among the recently described subtypes were DUX4 and PAX5 altered (PAX5alt). Using whole transcriptome RNA sequencing (RNA-Seq) in 377 B-ALL children from MaSpore ALL 2003/2010 (MS2003/MS2010) studies, we found that, after hyperdiploid and ETV6-RUNX1, the third and fourth most common subtypes were DUX4 (n= 51; 14%) and PAX5alt (n= 36; 10%). DUX4 also formed the largest genetic subtype among patients with poor Day 33 MRD (n=12/44). But despite the poor MRD, outcome of DUX4 B-ALL was excellent (5-year cumulative risk of relapse (CIR) 8.9% [95% CI, 2.8% to 19.5%], 5-year OS 97.8% [95% CI, 85.3% to 99.7%]). In MS2003, 21% DUX4 B-ALL had poor peripheral blood (PB) response to prednisolone at day 8, higher than other subtypes (8%; P=0.03). In MS2010, with vincristine at day 1, no day 8 poor PB response was observed in DUX4 subtype (P=0.03). PAX5alt group had an intermediate risk of relapse (5-year CIR 18.1%) but when IKZF1 was not deleted, outcome was excellent with no relapse among 23 patients. Compared to MS2003, outcome of PAX5alt B-ALL with IKZF1 co-deletion was improved by treatment intensification in MS2010 (5-year CIR 80.0% vs 0%; P=0.05). In conclusion, despite its poor initial response, DUX4 B-ALL had a favorable overall outcome, and the prognosis of PAX5alt was strongly dependent on IKZF1 co-deletion.

PURPOSE To investigate whether, for children with favorable-risk B-cell precursor ALL (BCP-ALL), an anthracycline-free protocol is noninferior to a modified Berlin-Frankfurt-Muenster ALL-IC2002 protocol, which includes 120 mg/m2 of anthracyclines. PATIENTS AND METHODS Three hundred sixty-nine children with favorable-risk BCP-ALL (age 1-9 years, no extramedullary disease, and no high-risk genetics) who cleared minimal residual disease (≤0.01%) at the end of remission induction were enrolled into Ma-Spore (MS) ALL trials. One hundred sixty-seven standard-risk (SR) patients (34% of Malaysia-Singapore ALL 2003 study [MS2003]) were treated with the MS2003-SR protocol and received 120 mg/m2 of anthracyclines during delayed intensification while 202 patients (42% of MS2010) received an anthracycline-free successor protocol. The primary outcome was a noninferiority margin of 1.15 in 6-year event-free survival (EFS) between the MS2003-SR and MS2010-SR cohorts. RESULTS The 6-year EFS of MS2003-SR and MS2010-SR (anthracycline-free) cohorts was 95.2% ± 1.7% and 96.5% ± 1.5%, respectively ( P = .46). The corresponding 6-year overall survival was 97.6% and 99.0% ± 0.7% ( P = .81), respectively. The cumulative incidence of relapse was 3.6% and 2.6%, respectively ( P = .42). After adjustment for race, sex, age, presenting WBC, day 8 prednisolone response, and favorable genetic subgroups, the hazard ratio for MS2010-SR EFS was 0.98 (95% CI, 0.84 to 1.14; P = .79), confirming noninferiority. Compared with MS2003-SR, MS2010-SR had significantly lower episodes of bacteremia (30% v 45.6%; P = .04) and intensive care unit admissions (1.5% v 9.5%; P = .004). CONCLUSION In comparison with MS2003-SR, the anthracycline-free MS2010-SR protocol is not inferior and was less toxic as treatment for favorable-risk childhood BCP-ALL.