Enhanced Risk Stratification for Children and Young Adults with B-Cell Acute Lymphoblastic Leukemia: A Children's Oncology Group Report.

Current strategies to treat pediatric acute lymphoblastic leukemia rely on risk stratification algorithms using categorical data. We investigated whether using continuous variables assigned different weights would improve risk stratification. We developed and validated a multivariable Cox model for relapse-free survival (RFS) using information from 21199 patients. We constructed risk groups by identifying cutoffs of the COG Prognostic Index (PICOG) that maximized discrimination of the predictive model. Patients with higher PICOG have higher predicted relapse risk. The PICOG reliably discriminates patients with low vs. high relapse risk. For those with moderate relapse risk using current COG risk classification, the PICOG identifies subgroups with varying 5-year RFS. Among current COG standard-risk average patients, PICOG identifies low and intermediate risk groups with 96% and 90% RFS, respectively. Similarly, amongst current COG high-risk patients, PICOG identifies four groups ranging from 96% to 66% RFS, providing additional discrimination for future treatment stratification. When coupled with traditional algorithms, the novel PICOG can more accurately risk stratify patients, identifying groups with better outcomes who may benefit from less intensive therapy, and those who have high relapse risk needing innovative approaches for cure.

Wwox-Brca1 interaction: role in DNA repair pathway choice.

In this study, loss of expression of the fragile site-encoded Wwox protein was found to contribute to radiation and cisplatin resistance of cells, responses that could be associated with cancer recurrence and poor outcome. WWOX gene deletions occur in a variety of human cancer types, and reduced Wwox protein expression can be detected early during cancer development. We found that Wwox loss is followed by mild chromosome instability in genomes of mouse embryo fibroblast cells from Wwox-knockout mice. Human and mouse cells deficient for Wwox also exhibit significantly enhanced survival of ionizing radiation and bleomycin treatment, agents that induce double-strand breaks (DSBs). Cancer cells that survive radiation recur more rapidly in a xenograft model of irradiated breast cancer cells; Wwox-deficient cells exhibited significantly shorter tumor latencies vs Wwox-expressing cells. This Wwox effect has important consequences in human disease: in a cohort of cancer patients treated with radiation, Wwox deficiency significantly correlated with shorter overall survival times. In examining mechanisms underlying Wwox-dependent survival differences, we found that Wwox-deficient cells exhibit enhanced homology directed repair (HDR) and decreased non-homologous end-joining (NHEJ) repair, suggesting that Wwox contributes to DNA DSB repair pathway choice. Upon silencing of Rad51, a protein critical for HDR, Wwox-deficient cells were resensitized to radiation. We also demonstrated interaction of Wwox with Brca1, a driver of HDR, and show via immunofluorescent detection of repair proteins at ionizing radiation-induced DNA damage foci that Wwox expression suppresses DSB repair at the end-resection step of HDR. We propose a genome caretaker function for WWOX, in which Brca1-Wwox interaction supports NHEJ as the dominant DSB repair pathway in Wwox-sufficient cells. Taken together, the experimental results suggest that reduced Wwox expression, a common occurrence in cancers, dysregulates DSB repair, enhancing efficiency of likely mutagenic repair, and enabling radiation and cisplatin treatment resistance.

Long-term follow-up of imatinib in pediatric Philadelphia chromosome-positive acute lymphoblastic leukemia: Children's Oncology Group study AALL0031.

We previously reported preliminary findings that post induction imatinib mesylate (340 mg/m(2)/day), in combination with intensive chemotherapy, resulted in outcomes similar to blood and marrow transplant (BMT) for pediatric patients with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). We now report 5-year outcomes of imatinib plus intensive chemotherapy in 91 children (1-21 years) with and without allogeneic BMT (N=91). We explore the impacts of additional chromosomal abnormalities and minimal residual disease (MRD) by flow cytometry on outcomes. The 5-year disease-free survival was similar for Cohort 5 patients, treated with chemotherapy plus imatinib (70%±12%, n=28), sibling donor BMT patients (65%±11%, n=21) and unrelated donor BMT patients (59±15%; P=0.60, n=13). Patients with additional cytogenetic abnormalities had worse outcomes (P=0.05). End induction (pre-imatinib) MRD was not prognostic for Cohort 5 or allogeneic BMT patients, although limited by small numbers. The re-induction rate following relapse was similar to other higher-risk ALL groups. Longer-term follow-up confirms our initial observation of substantially good outcomes for children and adolescents with Ph+ ALL treated with imatinib plus intensive chemotherapy with no advantage for allogeneic BMT.

An international study of intrachromosomal amplification of chromosome 21 (iAMP21): cytogenetic characterization and outcome.

Intrachromosomal amplification of chromosome 21 (iAMP21) defines a distinct cytogenetic subgroup of childhood B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). To date, fluorescence in situ hybridisation (FISH), with probes specific for the RUNX1 gene, provides the only reliable detection method (five or more RUNX1 signals per cell). Patients with iAMP21 are older (median age 9 years) with a low white cell count. Previously, we demonstrated a high relapse risk when these patients were treated as standard risk. Recent studies have shown improved outcome on intensive therapy. In view of these treatment implications, accurate identification is essential. Here we have studied the cytogenetics and outcome of 530 iAMP21 patients that highlighted the association of specific secondary chromosomal and genetic changes with iAMP21 to assist in diagnosis, including the gain of chromosome X, loss or deletion of chromosome 7, ETV6 and RB1 deletions. These iAMP21 patients when treated as high risk showed the same improved outcome as those in trial-based studies regardless of the backbone chemotherapy regimen given. This study reinforces the importance of intensified treatment to reduce the risk of relapse in iAMP21 patients. This now well-defined patient subgroup should be recognised by World Health Organisation (WHO) as a distinct entity of BCP-ALL.

Excess congenital non-synonymous variation in leukemia-associated genes in MLL- infant leukemia: a Children's Oncology Group report.

Infant leukemia (IL) is a rare sporadic cancer with a grim prognosis. Although most cases are accompanied by MLL rearrangements and harbor very few somatic mutations, less is known about the genetics of the cases without MLL translocations. We performed the largest exome-sequencing study to date on matched non-cancer DNA from pairs of mothers and IL patients to characterize congenital variation that may contribute to early leukemogenesis. Using the COSMIC database to define acute leukemia-associated candidate genes, we find a significant enrichment of rare, potentially functional congenital variation in IL patients compared with randomly selected genes within the same patients and unaffected pediatric controls. IL acute myeloid leukemia (AML) patients had more overall variation than IL acute lymphocytic leukemia (ALL) patients, but less of that variation was inherited from mothers. Of our candidate genes, we found that MLL3 was a compound heterozygote in every infant who developed AML and 50% of infants who developed ALL. These data suggest a model by which known genetic mechanisms for leukemogenesis could be disrupted without an abundance of somatic mutation or chromosomal rearrangements. This model would be consistent with existing models for the establishment of leukemia clones in utero and the high rate of IL concordance in monozygotic twins.

Genomic profiling in Down syndrome acute lymphoblastic leukemia identifies histone gene deletions associated with altered methylation profiles.

Patients with Down syndrome (DS) and acute lymphoblastic leukemia (ALL) have distinct clinical and biological features. Whereas most DS-ALL cases lack the sentinel cytogenetic lesions that guide risk assignment in childhood ALL, JAK2 mutations and CRLF2 overexpression are highly enriched. To further characterize the unique biology of DS-ALL, we performed genome-wide profiling of 58 DS-ALL and 68 non-DS (NDS) ALL cases by DNA copy number, loss of heterozygosity, gene expression and methylation analyses. We report a novel deletion within the 6p22 histone gene cluster as significantly more frequent in DS-ALL, occurring in 11 DS (22%) and only 2 NDS cases (3.1%) (Fisher's exact P=0.002). Homozygous deletions yielded significantly lower histone expression levels, and were associated with higher methylation levels, distinct spatial localization of methylated promoters and enrichment of highly methylated genes for specific pathways and transcription factor-binding motifs. Gene expression profiling demonstrated heterogeneity of DS-ALL cases overall, with supervised analysis defining a 45-transcript signature associated with CRLF2 overexpression. Further characterization of pathways associated with histone deletions may identify opportunities for novel targeted interventions.

Maternal vitamin and iron supplementation and risk of infant leukaemia: a report from the Children's Oncology Group.

BACKGROUND: Prenatal supplementation has been inversely associated with childhood, but not with infant, leukaemia. METHODS: Mothers of 443 cases of infant leukaemia diagnosed during 1996-2006 and 324 frequency-matched controls completed interviews. Associations were evaluated by unconditional logistic regression. RESULTS: We observed no associations between prenatal vitamin (odds ratio (OR)=0.79, 95% confidence interval (CI): 0.44-1.42) or iron supplementation (OR=1.07, 95% CI: 0.75-1.52) and infant leukaemia after adjustment for race/ethnicity and income. Similar results were observed for leukaemia subtypes analysed separately. CONCLUSION: The observed null associations may be attributable to high supplementation rates and/or national fortification programmes.

A phase I/II study of rituximab and etanercept in patients with chronic lymphocytic leukemia and small lymphocytic lymphoma.

Rituximab has modest activity in relapsed chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma but is associated with tumor necrosis factor-alpha (TNF-alpha) release that can cause CLL proliferation and inhibit apoptosis. We examined whether disruption of TNF-alpha by etanercept improves response to rituximab in CLL. Eligible patients had previously treated CLL with performance status 0-3. Patients received etanercept 25 mg subcutaneously twice weekly (weeks 1-5) and rituximab 375 mg/m(2) intravenously thrice weekly (weeks 2-5) using a phase I/II design. Primary end points were response and toxicity. The 36 enrolled patients had a median of two prior treatments; 50% were fludarabine refractory and 22% had del(17p13.1). Of the 34 response-evaluable patients, 10 (29%) responded, including 9 partial responses and 1 complete remission. Response was not affected by prior rituximab or fludarabine-refractory status, but no patients with del(17p13.1) responded. Median progression-free survival for responders was 9.0 months (range 1-43). Ten patients have had treatment-free intervals exceeding 12 months, including four who have remained untreated for 32, 43, 46 and 56 months. Adverse events were mild, including mild infusion reactions, transient cytopenias and grade 3 infections in 14% of the patients. The combination of etanercept and thrice weekly rituximab produces durable remissions in non-del(17p13.1) CLL patients and is well tolerated.

Specific cytogenetic abnormalities are associated with a significantly inferior outcome in children and adolescents with mature B-cell non-Hodgkin's lymphoma: results of the FAB/LMB 96 international study.

Clinical studies showed that advanced stage, high LDH, poor response to reduction therapy and combined bone marrow and central nervous system disease are significantly associated with a decreased event-free survival (EFS) in pediatric mature B-cell non-Hodgkin's lymphoma (B-NHL) treated on FAB/LMB96. Although rearranged MYC/8q24 (R8q24) is characteristic of Burkitt lymphoma (BL), little information is available on other cytogenetic abnormalities and their prognostic importance. We performed an international review of 238 abnormal karyotypes in childhood mature B-NHL treated on FAB/LMB96: 76% BL, 8% Burkitt-like lymphoma, 13% diffuse large B-cell lymphoma (DLBCL). The main BL R8q24-associated chromosomal aberrations were +1q (29%), +7q and del(13q) (14% each). The DLBCL appeared heterogeneous and more complex. Incidence of R8q24 (34%) was higher than reported in adult DLBCL. The prognostic value of cytogenetic abnormalities on EFS was studied by Cox model controlling for the known risk factors: R8q24, +7q and del(13q) were independently associated with a significant inferior EFS (hazard ratio: 6.1 (P=0.030), 2.5 (P=0.015) and 4.0 (P=0.0003), respectively). The adverse prognosis of R8q24 was observed only in DLBCL, whereas del(13q) and +7q had a similar effect in DLBCL and BL. These results emphasize the significant biological heterogeneity and the development of cytogenetic risk-adapted therapy in childhood mature B-NHL.

Filgrastim and alemtuzumab (Campath-1H) for refractory chronic lymphocytic leukemia.

Alemtuzumab (anti-CD52; Campath-1H) is effective in fludarabine-refractory chronic lymphocytic leukemia (CLL), but is associated with infection and early onset neutropenia. To reduce toxicity, filgrastim (G-CSF) was administered concurrently with alemtuzumab. In total, 14 CLL patients (median age 59) with a median of 3.5 prior regimens (range 1--12) received i.v. alemtuzumab, stepped up from 3 to 30 mg the first week, then 30 mg thrice weekly for 12 weeks. Filgrastim 5 microg/kg was administered daily 5 days before and throughout alemtuzumab therapy. Six patients developed cytomegalovirus (CMV) reactivation 3--6 weeks into treatment; six patients developed fever, three neutropenia, and one pneumonia. The patient with CMV pneumonia died; ganciclovir cleared CMV in the other patients. Five patients developed early neutropenia (weeks 2--5). Four patients developed delayed neutropenia (weeks 10--13) unassociated with CMV reactivation. Nine patients ceased therapy because of infectious and hematologic toxicity. Five partial responses were noted, all in patients with lymph nodes>cm, lasting a median of 6.5 months (range 5--13). Filgrastim and alemtuzumab were given concurrently with manageable infusion toxicity and clinical activity, but the efficacy of this regimen was limited by delayed neutropenia of unclear etiology and CMV reactivation. Filgrastrim should not be administered prophylactically during alemtuzumab therapy outside clinical trials.

High concordance from independent studies by the Children's Cancer Group (CCG) and Pediatric Oncology Group (POG) associating favorable prognosis with combined trisomies 4, 10, and 17 in children with NCI Standard-Risk B-precursor Acute Lymphoblastic Leukemia: a Children's Oncology Group (COG) initiative.

Chromosome aberrations have a major role in pediatric acute lymphoblastic leukemia (ALL) risk assignment. The Children's Cancer Group (CCG) and the Pediatric Oncology Group (POG) independently assessed the significance of trisomy for chromosomes 4, 10, and 17 in National Cancer Institute (NCI) Standard- and High-Risk ALL. Data from 1582 (CCG) and 3902 (POG) patients were analyzed. Eight-year event-free survivals (EFS) of 91% (CCG) and 89% (POG) (P < 0.001) were achieved in patients assigned to NCI Standard Risk whose leukemic cells had simultaneous trisomies 4, 10, and 17. Both groups showed the degree of favorable prognostic importance increased with the actual number of favorable trisomies. POG analyses also demonstrated hyperdiploidy (> or =53 chromosomes) was less of an independently significant prognostic factor in the absence of these key trisomies. This finding supported conclusions from previous CCG and POG studies that specific trisomies are more important than chromosome number in predicting outcome in pediatric B-precursor ALL. In NCI Higher Risk patients, the number of favorable trisomies was not prognostically significant, but showed the same trend. Moreover, specific trisomies 4, 10, and 17 remain associated with favorable prognosis in Standard-Risk B-precursor ALL, even in the context of very different treatment approaches between the groups.

No prognostic effect of additional chromosomal abnormalities in children with acute lymphoblastic leukemia and 11q23 abnormalities.

This study characterized the additional chromosomal abnormalities (ACA) associated with 11q23 rearrangements in 450 infants and children with acute lymphoblastic leukemia (ALL) and examined the impact of these ACA on survival. Overall, 213 (47%) cases had ACA but the incidence varied according to patient age and 11q23 subgroup. Infants and patients with t(4;11)(q21;q23) had the lowest incidence of ACA (50/182 (27%) and 57/216 (26%) respectively), whereas patients with del(11)(q23) had the highest incidence (66/93 (71%)). Del(11)(q23) abnormalities were heterogeneous and occasionally secondary to t(9;22)(q34;q11.2). Thus, patients with del(11)(q23) comprised a separate biological entity, which was clearly distinct from those with an 11q23 translocation. The most frequent specific ACA were trisomy X (n = 38), abnormal 12p (n = 32), abnormal 9p (n = 28) and del(6q) (n = 19). The presence of ACA did not change the 5 year event-free survival estimates among children (56% (95% Cl 46-65%) vs 62% (54-69%)) or infants (22% (15-29%) vs 18% (9-29%)), nor when the different 11q23 subgroups were analyzed separately. This study has conclusively demonstrated that there is no prognostic effect of secondary chromosomal changes in association with 11q23 abnormalities in childhood ALL. However, characterization of these ACA is important to determine their potential role in initiation of MLL driven leukemogenesis.