Faculty Bibliography

We sequenced 120 candidate genes in 187 high-risk childhood B-precursor acute lymphoblastic leukemias, the largest pediatric cancer genome sequencing effort reported to date. Integrated analysis of 179 validated somatic sequence mutations with genome-wide copy number alterations and gene expression profiles revealed a high frequency of recurrent somatic alterations in key signaling pathways, including B-cell development/differentiation (68% of cases), the TP53/RB tumor suppressor pathway (54%), Ras signaling (50%), and Janus kinases (11%). Recurrent mutations were also found in ETV6 (6 cases), TBL1XR1 (3), CREBBP (3), MUC4 (2), ASMTL (2), and ADARB2 (2). The frequency of mutations within the 4 major pathways varied markedly across genetic subtypes. Among 23 leukemias expressing a BCR-ABL1-like gene expression profile, 96% had somatic alterations in B-cell development/differentiation, 57% in JAK, and 52% in both pathways, whereas only 9% had Ras pathway mutations. In contrast, 21 cases defined by a distinct gene expression profile coupled with focal ERG deletion rarely had B-cell development/differentiation or JAK kinase alterations but had a high frequency (62%) of Ras signaling pathway mutations. These data extend the range of genes that are recurrently mutated in high-risk childhood B-precursor acute lymphoblastic leukemia and highlight important new therapeutic targets for selected patient subsets.

Children's Cancer Group-1991 selected 2 components from the Children's Cancer Group studies shown to be effective in high-risk acute lymphoblastic leukemia and examined them in children with National Cancer Institute standard-risk acute B-precursor lymphoblastic leukemia. These were (1) vincristine and escalating IV methotrexate (MTX) without leucovorin rescue during the interim maintenance (IM) phases and (2) addition of a second delayed intensification (DI) phase. Eligible patients (n = 2078) were randomly assigned to regimens containing either oral (PO) MTX, PO mercaptopurine, dexamethasone, and vincristine or IV MTX during IM phases, and regimens with either single DI or double DI. Five-year event-free survival (EFS) and overall survival for patients on the PO MTX arms were 88.7% +/- 1.4% and 96% +/- 0.9% versus 92.6% +/- 1.2% and 96.5% +/- 0.8% for those on the IV MTX arms (P = .009, P = .66). Five-year EFS and overall survival for patients who received single DI were 90.9% +/- 1.3% and 97.1% +/- 0.8% versus 90.5% +/- 1.3% and 95.4% +/- 3.8% for those who received double DI (P = .71, P = .12). No advantage was found for a second DI; however, replacement of PO MTX, PO mercaptopurine, vincristine, and dexamethasone during IM with vincristine and escalating IV MTX improved EFS.

Persistent anxiety is common among parents of children with cancer and may affect the family's well-being and adjustment. The goals of this pilot study are to determine the feasibility and potential efficacy of a brief cognitive-behavioral parent intervention aimed at reducing parental distress and anxiety related to their child's cancer diagnosis. Parents of children with cancer, at least 1 month postdiagnosis, were screened at an outpatient oncology clinic, and those reporting elevated levels of distress were offered a 4-session cognitive-behavioral intervention based on a modified version of the Surviving Cancer Competently Intervention Program-Newly Diagnosed. Five parents reporting persistent distress received the intervention. Results revealed decreases in parents' distress, state anxiety, and depressive symptoms, as well as in parents' feelings of burden associated with their children's cancer. This initial study suggests that identification of parents with prolonged heightened psychological distress is feasible and acceptable and that offering them a brief intervention within a pediatric oncology setting may be beneficial

While intensification of therapy has improved event-free survival (EFS) and survival in newly diagnosed children with acute lymphoblastic leukemia (ALL), postrelapse outcomes remain poor. It might be expected that patients relapsing after inferior initial therapy would have a higher retrieval rate than after superior therapy. In the Children's Oncology Group Study CCG-1961, significantly superior EFS and survival were achieved with an augmented (stronger) versus standard intensity regimen of postinduction intensification (PII) for children with newly diagnosed high-risk ALL and rapid day 7 marrow response (EFS/survival 81.2%/88.7% vs 71.7%/83.4%, respectively). This provided an opportunity to evaluate postrelapse survival (PRS) in 272 relapsed patients who had received randomly allocated initial treatment with augmented or standard intensity PII. As expected, PRS was worse for early versus late relapse, marrow versus extramedullary site, adolescent versus younger age and T versus B lineage. However, no difference in 3-year PRS was detected for having received augmented versus standard intensity PII (36.4% +/- 5.7% vs 39.2% +/- 4.1%; log rank P = .72). Similar findings were noted within subanalyses by timing and site of relapse, age, and immunophenotype. These findings provide insight into mechanisms of relapse in ALL, and are consistent with emergence of a resistant subclone that has acquired spontaneous mutations largely independent of initial therapy. This study is registered at www.clinicaltrials.gov as NCT00002812.

Although five-year survival rates for childhood acute lymphoblastic leukemia (ALL) are now over 80% in most industrialized countries, not all children have benefited equally from this progress. Ethnic differences in survival after childhood ALL have been reported in many clinical studies, with poorer survival observed among African Americans or those with Hispanic ethnicity when compared with European Americans or Asians. The causes of ethnic differences remain uncertain, although both genetic and non-genetic factors are likely important. Interrogating genome-wide germline SNP genotypes in an unselected large cohort of children with ALL, we observed that the component of genomic variation that co-segregated with Native American ancestry was associated with risk of relapse (P = 0.0029) even after adjusting for known prognostic factors (P = 0.017). Ancestry-related differences in relapse risk were abrogated by the addition of a single extra phase of chemotherapy, indicating that modifications to therapy can mitigate the ancestry-related risk of relapse.

PURPOSE: We review recent advances in the biologic understanding and treatment of childhood acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), identify therapeutically challenging subgroups, and suggest future directions of research. METHODS: A review of English literature on childhood acute leukemias from the past 5 years was performed. RESULTS: Contemporary treatments have resulted in 5-year event-free survival rates of approximately 80% for childhood ALL and almost 60% for pediatric AML. The advent of high-resolution genome-wide analyses has provided new insights into leukemogenesis and identified many novel subtypes of leukemia. Virtually all ALL and the vast majority of AML cases can be classified according to specific genetic abnormalities. Cooperative mutations involved in cell differentiation, cell cycle regulation, tumor suppression, drug responsiveness, and apoptosis have also been identified in many cases. The development of new formulations of existing drugs, molecularly targeted therapy, and immunotherapies promises to further advance the cure rates and improve quality of life of patients. CONCLUSION: The application of new high-throughput sequencing techniques to define the complete DNA sequence of leukemia and host normal cells and the development of new agents targeted to leukemogenic pathways promise to further improve outcome in the coming decade.