Despite current risk-directed therapy, approximately 15-20% of pediatric patients with acute lymphoblastic leukemia (ALL) have relapses. Recent genome-wide analyses have identified that an alteration of IKZF1 is associated with very poor outcomes in B-cell progenitor ALL. In this study, we determined the prognostic significance of IKZF1 deletions in patients with childhood ALL. This study analyzed 242 pediatric B-cell progenitor ALL patients in Taiwan. We developed a simple yet sensitive multiplex quantitative PCR coupled with capillary electrophoresis to accurately determine the allele dose of IKZF1, and high resolution melting was used for mutation screening for all coding exons of IKZF1. Twenty-six (10.7%) pediatric B-cell progenitor ALL patients were found to harbor these deletions. Most of the deletions were broader deletions that encompassed exon 3 to exon 6, consistent with previous reports. Genomic sequencing of IKZF1 was carried out in all cases and no point mutations were identified. Patients with IKZF1 deletions had inferior event-free survival (P < 0.001), and overall survival (P = 0.0016). The association between IKZF1 deletions and event-free survival was independent of age, leukocyte count at presentation, and cytogenetic subtype by multivariate Cox analysis (P = 0.003, hazard ratio = 2.45). This study indicates that detection of IKZF1 deletions upon diagnosis of B-cell progenitor ALL may help to identify patients at risk of treatment failure. IKZF1 deletions could be incorporated as a new high-risk prognostic factor in future treatment protocols. To the best of our knowledge, this is the first study to examine the poor prognosis of IKZF1 deletions in an Asian population.

TP53 alterations are frequent relapse‐acquired mutations in childhood acute lymphoblastic leukemia (ALL). The present study evaluated the clinical significance of relapsed childhood ALL in Taiwan. Diagnostic and/or relapsed bone marrow or peripheral blood was obtained from 111 children with relapsed ALL who were initially treated by using Taiwan Pediatric Oncology Group (TPOG) ALL protocols from January 1997 to May 2018. Mutations were detected by PCR and sequencing, as well as by multiplex ligation‐dependent probe amplification to detect copy number alterations. Copy number and/or sequence alterations of TP53 were detected in 29% (28 of 98) and in 46% (6 of 13) of patients with relapsed B‐cell and T‐cell ALL, respectively. This incidence was much higher than that in several similar studies conducted in Caucasian populations. Seventy percent of all TP53 alterations were gained at relapse in 67 matched samples by back‐tracking matched diagnostic samples. TP53 alterations were associated with lower 5‐year event‐free survival (EFS) and overall survival (OS) rates (P = .013 and P = .0002, respectively). Multivariate analysis confirmed the prognostic significance of TP53 alterations. Forty‐five patients received hematopoietic stem‐cell transplantations post‐relapse. Patients with TP53 alterations (14/45) had inferior 5‐year EFS and OS than patients without TP53 alterations after transplantation (P = .002 and P = .001, respectively). The significance of these TP53 alterations for patients who received transplantations was confirmed by multivariate analysis. In conclusion, TP53 alterations were enriched and useful as prognostic markers in relapsed childhood ALL.

Background. Discontinuation of E. coli L-asparaginase in patients with acute lymphoblastic leukemia (ALL) is unavoidable upon severe allergic reaction. We sought to examine outcomes following E. coli L-asparaginase discontinuation due to severe allergic reactions. Procedure. We evaluated the outcome of children enrolled in Taiwan Pediatric Oncology Group-2002-ALL protocol between 2002 and 2012, who had E. coli L-asparaginase discontinued due to severe allergic reactions, and compared the outcomes of those who continued with Erwinia L-asparaginase (Erwinase) with those who did not. Results. Among 700 patients enrolled in this study, 33 patients had E. coli L-asparaginase treatment discontinued due to severe allergic reactions. Five-year overall survival did not differ significantly among the 648 patients without discontinuation (81 ± 1.6%, mean ± SE), compared to 17 patients with allergic reactions and treated with Erwinase (88 ± 7.8%) and 16 patients with allergic reactions but not treated with Erwinase (87 ± 8.6%). Among 16 patients who did not receive Erwinase, all 10 who received ࣙ50% of the scheduled doses of E. coli L-asparaginase before discontinuation survived without events. Conclusions. Erwinase treatment may not be needed for some ALL patients with severe allergy to E. coli L-asparaginase if ࣙ50% of prescribed doses were received and/or therapy is augmented with other agents.

Background To eliminate cranial irradiation (CrRT)–related sequelae and to minimize the adverse impact of traumatic lumbar puncture (TLP) with blasts, the Taiwan Pediatric Oncology Group (TPOG) introduced a modified central nervous system (CNS)–directed regimen characterized by delayed triple intrathecal therapy (TIT) and the omission of CrRT for all children with newly diagnosed acute lymphoblastic leukemia (ALL). Methods This study compared the treatment outcomes of patients overall and patients with a non–CNS‐1 status (CNS‐2, CNS‐3, or TLP with blasts) in 2 treatment eras, one before and another after the revision of the TPOG‐ALL‐2002 protocol by the introduction of the modification (era 1 [2002‐2008] with CrRT and era 2 [2009‐2012] with delayed first TIT and no CrRT). Results There were no statistically significant differences in major outcomes between the 903 patients treated in era 1 and the 444 patients treated in era 2: the 5‐year event‐free survival (EFS) rates were 75.7% ± 1.4% and 72.1% ± 2.4%, respectively (P = .260), and the cumulative risks of isolated CNS relapse were 4.0% ± 0.7% and 4.1% ± 1.0%, respectively (P = .960). There were also no differences between non–CNS‐1 patients treated in era 1 (n = 76) and era 2 (n =28): the 5‐year EFS rates were 52.3% ± 5.8% and 62.9% ± 9.4%, respectively (P = .199), and the cumulative risks of isolated CNS relapse were 6.3% ± 3.1% and 3.6% ± 3.5%, respectively (P = .639). Notably, TLP with blasts was completely eliminated after the first TIT was delayed in era 2. Conclusions The delay of the first TIT until the clearance of circulating blasts and the total omission of CrRT did not compromise survival or CNS control in patients with childhood ALL, including those with a non–CNS‐1 status.

For SR patients, one-course reinduction was adequate. Triple intrathecal therapy alone successfully prevented CNS relapse.