Analysis of 2668 children with acute lymphoblastic leukemia (ALL) treated in two successive Nordic clinical trials (Nordic Society of Paediatric Haematology and Oncology (NOPHO) ALL-92 and ALL-2000) showed that 75% of all patients are cured by first-line therapy, and 83% are long-term survivors. Improvements in systemic and intrathecal chemotherapy have reduced the use of central nervous system (CNS) irradiation to o10% of the patients and provided a 5-year risk of isolated CNS relapse of 2.6%. Improved risk stratification and chemotherapy have eliminated the previous independent prognostic significance of gender, CNS leukemia and translocation t(1;19)(q23;p13), whereas the post-induction level of minimal residual disease (MRD) has emerged as a new risk grouping feature. Infant leukemia, high leukocyte count, T-lineage immunophenotype, translocation t(4;11)(q21;q23) and hypodiploidy persist to be associated with lower cure rates. To reduce the overall toxicity of the treatment, including the risk of therapy-related second malignant neoplasms, the current NOPHO ALL-2008 protocol does not include CNS irradiation in first remission, the dose of 6-mercaptopurine is reduced for patients with low thiopurine methyltransferase activity, and the protocol restricts the use of hematopoietic stem cell transplantation in first remission to patients without morphological remission after induction therapy or with high levels of MRD after 3 months of therapy.

Adults with acute lymphoblastic leukemia (ALL) do worse than children. From 7/2008 to 12/2014, Nordic and Baltic centers treated 1509 consecutive patients aged 1-45 years with Philadelphia chromosome-negative ALL according to the NOPHO ALL2008 without cranial irradiation. Overall, 1022 patients were of age 1-9 years (A), 266 were 10-17 years (B) and 221 were 18-45 years (C). Sixteen patients (three adults) died during induction. All others achieved remission after induction or 1-3 intensive blocks. Subsequently, 45 patients (12 adults) died, 122 patients relapsed (32 adults) with a median time to relapse of 1.6 years and 13 (no adult) developed a second malignancy. Median follow-up time was 4.6 years. Among the three age groups, older patients more often had higher risk ALL due to T-ALL (32%/25%/9%, P<0.001), KMT2A rearrangements (6%/5%/3%, P<0.001) and higher day 29 residual leukemia for B-lineage (P<0.001), but not T-ALL (P=0.53). Event-free survival rates (pEFS) were 89±1% (A), 80±3% (B) and 74±4% (C) with significant differences only for non-high risk groups. Except for thrombosis, pancreatitis and osteonecrosis, the risk of 19 specified toxicities was not enhanced by age above 10 years. In conclusion, a pediatric-based protocol is tolerable and effective for young adults, despite their increased frequency of higher risk features.

BackgroundAlthough aberrant DNA methylation has been observed previously in acute lymphoblastic leukemia (ALL), the patterns of differential methylation have not been comprehensively determined in all subtypes of ALL on a genome-wide scale. The relationship between DNA methylation, cytogenetic background, drug resistance and relapse in ALL is poorly understood.ResultsWe surveyed the DNA methylation levels of 435,941 CpG sites in samples from 764 children at diagnosis of ALL and from 27 children at relapse. This survey uncovered four characteristic methylation signatures. First, compared with control blood cells, the methylomes of ALL cells shared 9,406 predominantly hypermethylated CpG sites, independent of cytogenetic background. Second, each cytogenetic subtype of ALL displayed a unique set of hyper- and hypomethylated CpG sites. The CpG sites that constituted these two signatures differed in their functional genomic enrichment to regions with marks of active or repressed chromatin. Third, we identified subtype-specific differential methylation in promoter and enhancer regions that were strongly correlated with gene expression. Fourth, a set of 6,612 CpG sites was predominantly hypermethylated in ALL cells at relapse, compared with matched samples at diagnosis. Analysis of relapse-free survival identified CpG sites with subtype-specific differential methylation that divided the patients into different risk groups, depending on their methylation status.ConclusionsOur results suggest an important biological role for DNA methylation in the differences between ALL subtypes and in their clinical outcome after treatment.