Association of CEP72 rs924607 TT Genotype with Vincristine-induced Peripheral Neuropathy Measured by Motor Nerve Conduction Studies.

Vincristine is at the core of many treatment protocols for childhood malignancies. The major dose-limiting side effect is vincristine-induced peripheral neuropathy (VIPN) which may cause morbidity and disrupt curative treatment. Several studies have tried to identify pharmacogenetic biomarkers for susceptibility to vincristine-induced toxicity (Egbelakin A et al., Pediatr Blood Cancer 2011; 56: 361-367. Aplenc R et al., Br J Haematol 2003; 122: 240-244. Diouf B et al., JAMA 2015; 313: 815-823. Zgheib NK et al., Pharmacogenet Genomics, 2018; 28: 189-195. Gutierrez-Camino A et al., Pharmacogenet Genomics 2016; 26: 100-102. Wright GE et al., Clin Pharmacol Ther 2019; 105: 402-410. Kayilioglu H et al., J Pediatr Hematol Oncol 2017; 39(6): 458-462). A major limitation of these studies is that VIPN is difficult to measure objectively using only clinical examination and clinical scales. This is especially true for children, who are often unable to report or grade symptoms such as paresthesia, numbness, and pain. Furthermore, some studies are questioning the validity of currently available neuropathy grading scales (Postma TJ et al., Ann Oncol 1998; 9: 739-744). Our group recently showed that electrophysiological studies can be used with great accuracy for early detection of VIPN (Kavcic M et al., J Pediatr Hematol Oncol 2017; 39: 266-271). In the previous study, we found that VIPN presents with primary axonal involvement and is more pronounced on motor neurons (Kavcic M et al., J Pediatr Hematol Oncol 2017; 39: 266-271).

Genomic architecture and treatment outcome in pediatric acute myeloid leukemia: a Children's Oncology Group report.

Childhood acute myeloid leukemia (AML) is frequently characterized by chromosomal instability. Approximately 50% of patients have disease relapse, and novel prognostic markers are needed to improve risk stratification. We performed genome-wide genotyping in 446 pediatric patients with de novo AML enrolled in Children's Oncology Group (COG) studies AAML0531, AAML03P1, and CCG2961. Affymetrix and Illumina Omni 2.5 platforms were used to evaluate copy-number alterations (CNAs) and determine their associations with treatment outcome. Data from Affymetrix and Illumina studies were jointly analyzed with ASCAT and GISTIC software. An average of 1.14 somatically acquired CNAs per patient were observed. Novel reoccurring altered genomic regions were identified, and the presence of CNAs was found to be associated with decreased 3-year overall survival (OS), event-free survival (EFS), and relapse risk from the end of induction 1 (hazard ratio [HR], 1.7; 95% confidence interval [CI], 1.2-2.4; HR, 1.4; 95% CI, 1.0-1.8; and HR, 1.4; 95% CI, 1.0-2.0, respectively). Analyses by risk group demonstrated decreased OS and EFS in the standard-risk group only (HR, 1.9; 95% CI, 1.1-3.3 and HR, 1.7; 95% CI, 1.1-2.6, respectively). Additional studies are required to test the prognostic significance of CNA presence in disease relapse in patients with AML. COG studies AAML0531, AAML03P1, and CCG2961 were registered at www.clinicaltrials.gov as #NCT01407757, #NCT00070174, and #NCT00003790, respectively.

Parvovirus B19-associated Hemophagocytic Lymphohistiocytosis in a Patient With Glucose-6-phosphate Dehydrogenase Deficiency.

We report a case of a 12-year-old male with glucose-6-phosphate dehydrogenase deficiency presenting with clinical signs of sepsis and pancytopenia. Investigations revealed parvovirus B19 (PVB19)-associated hemophagocytic lymphohistiocytosis (HLH). The patient recovered fully and quickly with symptomatic treatment. Current evidence suggests that PVB19-associated HLH has a favorable prognosis. Mild undiagnosed cases of HLH may be the cause of pancytopenia in PVB19 infections.

Electrophysiological Studies to Detect Peripheral Neuropathy in Children Treated With Vincristine.

Patients treated with vincristine predictably develop peripheral neuropathy. The aim of our study was to investigate the pattern of vincristine-induced neuropathy in children by nerve conduction studies and somatosensory-evoked potentials (SSEPs). We included data from 39 children who received vincristine for various pediatric malignancies, and we performed initial and follow-up (after a minimum of 4 doses of vincristine 1.5 mg/m) conduction studies in 27 patients and SSEPs studies in 34 patients. On follow-up the most prevalent symptoms were paresthesias (44%) and constipation (22%), and the most common neurological sign was impaired myotatic reflexes (89%). Performing nerve conduction studies we found that significant reductions were measured for distal amplitudes, distal latencies were prolonged, and conduction velocities were relatively preserved. The most pronounced differences in amplitudes and distal latencies were measured in the peroneal nerves. Changes of SSEPs studies were subtle. Vincristine-induced neuropathy presents with primary axonal involvement and is more pronounced on motor neurons. We found a trend between higher age and higher dose and the degree of neuropathy in our group of patients.

Dexrazoxane exposure and risk of secondary acute myeloid leukemia in pediatric oncology patients.

BACKGROUND: Dexrazoxane may reduce anthracycline-associated cardiotoxicity in pediatric cancer patients. However, concerns of secondary acute myeloid leukemia (AML) have led to restrictions on pediatric dexrazoxane use in Europe. Published data about dexrazoxane-associated secondary AML are limited and conflicting. We sought to estimate the secondary AML risk in children receiving dexrazoxane after anthracycline exposure. PROCEDURE: A retrospective cohort of children with newly identified malignancies (excluding AML) receiving anthracyclines between January 1, 1999 and March 31, 2011 was established using the Pediatric Health Information System (PHIS). Patients were followed for all subsequent admissions to identify dexrazoxane exposures and secondary AML, defined by AML ICD-9 codes and AML induction chemotherapy. Logistic regression was used to model the association of dexrazoxane and secondary AML risk. A propensity score was used to adjust for measurable confounding. RESULTS: Of 15,532 patients in the cohort exposed to anthracyclines, 1,406 received dexrazoxane. The secondary AML rate was 0.21% (3 of 1,046) in dexrazoxane-exposed and 0.55% (77 of 14,126) in unexposed patients. In a propensity score-adjusted multivariate analysis, dexrazoxane exposure was not associated with an increased risk of secondary AML, OR = 0.38, 95% CI 0.11-1.26. CONCLUSIONS: Dexrazoxane was not associated with an increased risk of secondary AML in a large cohort of pediatric cancer patients receiving anthracyclines in US hospitals. While these data support dexrazoxane's safety in the general pediatric oncology population, additional studies are needed to confirm these findings and to quantify dexrazoxane's long-term cardioprotective effects.

Antifungal prophylaxis associated with decreased induction mortality rates and resources utilized in children with new-onset acute myeloid leukemia.

BACKGROUND: Invasive fungal infections cause significant morbidity and mortality for children with acute myeloid leukemia (AML). Data on the comparative effectiveness of antifungal prophylaxis in this population are limited. METHODS: A pediatric AML cohort was assembled from the Pediatric Health Information System database using ICD-9 codes and pharmacy data. Antifungal prophylaxis status was determined by pharmaceutical data review within 21 days of starting induction chemotherapy. Patients were followed until end of induction, death, or loss to follow-up. Cox regression analyses compared induction mortality and resources utilized between patients receiving and not receiving antifungal prophylaxis. A propensity score accounted for variation in demographic factors, location of care, and severity of illness at presentation. RESULTS: Eight hundred seventy-one AML patients were identified; the induction case fatality rate was 3.7%. In the adjusted Cox regression model, patients receiving antifungal prophylaxis (57%) had a decreased hazard for induction mortality (hazard ratio [HR], 0.42; 95% confidence interval [CI], .19-.90). Children receiving prophylaxis were less frequently exposed to broad-spectrum gram-positive (incidence rate ratio [IRR], 0.87; 95% CI, .79-.97) and antipseudomonal ß-lactam agents (HR, 0.91; 95% CI, .85-.96), had fewer blood cultures (IRR, 0.78; 95% CI, .71-.86), and had fewer chest CT scans (IRR, 0.73; 95% CI, .60-.88). CONCLUSIONS: Antifungal prophylaxis in pediatric AML patients was associated with reduced induction mortality rates and supportive care resources. Further investigation is necessary to determine whether antifungal prophylaxis should include antimold activity.

Induction mortality, ATRA administration, and resource utilization in a nationally representative cohort of children with acute promyelocytic leukemia in the United States from 1999 to 2009.

BACKGROUND: Limited data exist on induction mortality of pediatric patients with acute promyelocytic leukemia in the United States, usage of all-trans retinoic acid (ATRA) during acute promyelocytic leukemia induction, and the resources needed to deliver induction therapy. PROCEDURE: Using the Pediatric Health Information System database we established a retrospective cohort of patients treated for newly diagnosed acute promyelocytic leukemia with ATRA between January 1999 and September 2009 in 32 of 43 PHIS contributing free-standing pediatric hospitals in the United States. Standard statistical methods were used to determine in-hospital induction mortality, ATRA administration, and resource utilization during a 60-day observation period. RESULTS: A total of 163 children were identified who met eligibility criteria for cohort inclusion; 52% were female and 76% were white with an average age of 12.7 years. A total of 12 patients (7.4%) died, with 7 (58.3%) dying within the first 7 days of first admission. The mean time to first ATRA exposure increased with decreasing age (P = 0.0016). Resource utilization for management of retinoic acid syndrome was higher than anticipated based on prior studies and differed significantly from patients with non-M3 acute myeloid leukemia. CONCLUSIONS: The induction mortality for pediatric acute promyelocytic leukemia remains substantial with wide variation in ATRA administration and high rates of resource utilization.

Establishing a high-risk neuroblastoma cohort using the Pediatric Health Information System Database.

International Classification of Diseases, 9th Revision (ICD-9) code(s) for neuroblastoma do not exist, preventing identification of these patients in administrative databases. To overcome this challenge, a three-step algorithm, using ICD-9 codes, exclusion criteria, and manual review of chemotherapy billing data, was utilized to assemble a high-risk neuroblastoma cohort (n = 952) from the Pediatric Health Information System (PHIS) Database and validated at a single institution [sensitivity 89.1%; positive predictive value (PPV) 96.1%]. This cohort provides a data source for future comparative effectiveness and clinical epidemiology studies in high-risk neuroblastoma patients.

Patient and hospital factors associated with induction mortality in acute lymphoblastic leukemia.

BACKGROUND: Deaths during induction chemotherapy for pediatric acute lymphoblastic leukemia (ALL) account for one-tenth of ALL-associated mortality and half of ALL treatment-related mortality. We sought to ascertain patient- and hospital-level factors associated with induction mortality. PROCEDURE: We performed a retrospective cohort analysis of 8,516 children ages 0 to <19 years with newly diagnosed ALL admitted to freestanding US children's hospitals from 1999 to 2009 using the Pediatric Health Information System database. Induction mortality risk was modeled accounting for demographics, intensive care unit-level interventions, and socioeconomic status (SES) using Cox regression. The association of ALL induction mortality with hospital-level factors including volume, hospital-wide mortality and payer mix was analyzed with multiple linear regression. RESULTS: ALL induction mortality was 1.12%. Race and patient-level SES factors were not associated with induction mortality. Patients receiving both mechanical ventilation and vasoactive infusions experienced nearly 50% mortality (hazard ratio 122.30, 95% CI 66.56-224.80). Institutions in the highest induction mortality quartile contributed 27% of all patients but nearly half of all deaths (47 of 95). Hospital payer mix was associated with ALL induction mortality after adjustment for other hospital-level factors (P = 0.046). CONCLUSIONS: The overall risk of induction death is low but substantially increased in patients with cardio-respiratory and other organ failures. Induction mortality varies up to three-fold across hospitals and is correlated with hospital payer mix. Further work is needed to improve induction outcomes in hospitals with higher mortality. These data suggest an induction mortality rate of less than 1% may be an attainable national benchmark.

Outcome of pediatric acute myeloid leukemia patients receiving intensive care in the United States.

OBJECTIVE: Children with acute myeloid leukemia are at risk for sepsis and organ failure. Outcomes associated with intensive care support have not been studied in a large pediatric acute myeloid leukemia population. Our objective was to determine hospital mortality of pediatric acute myeloid leukemia patients requiring intensive care. DESIGN: Retrospective cohort study of children hospitalized between 1999 and 2010. Use of intensive care was defined by utilization of specific procedures and resources. The primary endpoint was hospital mortality. SETTING: Forty-three children's hospitals contributing data to the Pediatric Health Information System database. PATIENTS: Patients who are newly diagnosed with acute myeloid leukemia and who are 28 days through 18 years old (n = 1,673) hospitalized any time from initial diagnosis through 9 months following diagnosis or until stem cell transplant. A reference cohort of all nononcology pediatric admissions using the same intensive care resources in the same time period (n = 242,192 admissions) was also studied. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: One-third of pediatric patients with acute myeloid leukemia (553 of 1,673) required intensive care during a hospitalization within 9 months of diagnosis. Among intensive care admissions, mortality was higher in the acute myeloid leukemia cohort compared with the nononcology cohort (18.6% vs 6.5%; odds ratio, 3.23; 95% CI, 2.64-3.94). However, when sepsis was present, mortality was not significantly different between cohorts (21.9% vs 19.5%; odds ratio, 1.17; 95% CI, 0.89-1.53). Mortality was consistently higher for each type of organ failure in the acute myeloid leukemia cohort versus the nononcology cohort; however, mortality did not exceed 40% unless there were four or more organ failures in the admission. Mortality for admissions requiring intensive care decreased over time for both cohorts (23.7% in 1999-2003 vs 16.4% in 2004-2010 in the acute myeloid leukemia cohort, p = 0.0367; and 7.5% in 1999-2003 vs 6.5% in 2004-2010 in the nononcology cohort, p < 0.0001). CONCLUSIONS: Pediatric patients with acute myeloid leukemia frequently required intensive care resources, with mortality rates substantially lower than previously reported. Mortality also decreased over the time studied. Pediatric acute myeloid leukemia patients with sepsis who required intensive care had a mortality comparable to children without oncologic diagnoses; however, overall mortality and mortality for each category of organ failure studied was higher for the acute myeloid leukemia cohort compared with the nononcology cohort.

PAX5 Alterations in a Consecutive Childhood B-Cell Acute Lymphoblastic Leukemia Cohort Treated Using the ALL IC-BFM 2009 Protocol.

In this study, we aimed to identify patients within our B-ALL cohort with altered PAX5. Our objective was to use a comprehensive analysis approach to characterize the types of genetic changes, determine their origin (somatic/germline), and analyze the clinical outcomes associated with them. A consecutive cohort of 99 patients with B-ALL treated at the Children's Hospital of the UMC Ljubljana according to the ALL IC-BFM 2009 protocol was included in our study. We used RNA sequencing data for gene expression analysis, fusion gene detection and single nucleotide variant identification, multiplex-ligation dependent probe amplification for copy number variation assessment, and Sanger sequencing for germline variant detection. PAX5 was impacted in 33.3% of our patients, with the genetic alterations ranging from CNVs and rearrangements to SNVs. The most common were CNVs, which were found in more than a third of patients, followed by point mutations in 5.2%, and gene rearrangements in 4.1%. We identified eight patients with a PAX5-associated genetic subtype that were previously classified as "B-other", and they showed intermediate outcomes. We showed higher minimal residual disease values at the end of induction and poorer event-free survival in hyperdiploid cases carrying duplications in PAX5 compared to other hyperdiploid cases. We also report an interesting case of a patient with PAX5::FKBP15 and a pathogenic variant in PTPN11 who underwent an early relapse with a monocytic switch. In conclusion, this study provides valuable insights into the presence, frequency, and prognostic significance of diverse PAX5 alterations in B-ALL patients, highlighting the complexity of genetic factors and their impact on patient outcomes.

Genetic profiling of NUDT15 in the Slovenian population.

Determining variant TPMT alleles to predict patient response to thiopurine therapy represents one of the first successful implementations of pharmacogenomics in clinical practice. However, despite the TPMT-adjusted thiopurine dosing, some TPMT wild-type patients still exhibit toxicity at standard doses. Over the past decade, the pharmacogene NUDT15 has emerged as a significant co-modulator of thiopurine therapy. Initially, NUDT15 was considered important predominantly in Asian populations, but recent studies have highlighted its relevance in European populations as well.To evaluate the pharmacogenetic significance of NUDT15 in the Slovenian population, we sequenced extended regions of exon 1 and exon 3 in 109 healthy individuals and 37 patients with acute lymphoblastic leukemia.We identified eight variants, including one with established clinical significance (allele *3) and one extremely rare variant (Chr13 at 48045861; GRCh38, NC_000013.11). The frequencies of most previously described variants in both the general population and in the ALL cohort were consistent with those reported in other European populations, except for rs45465203, which was less frequent in the Slovenian population. None of the variants, except for NUDT15*3, were associated with cumulative thiopurine doses in ALL patients. However, these variants warrant further investigation in larger ALL cohorts.

Pharmacogenes are genes coding for enzymes, transporters and drug targets that can affect an individual's response to drugs. Determining genetic variants in pharmacogenes prior to treatment enables more personalized and effective treatments. NUDT15 is a gene that plays a crucial role in the metabolism of cytostatic and immunosuppressive drugs, specifically thiopurines, which are commonly used in the treatment of acute lymphoblastic leukemia (ALL). Certain genetic variants can result in lower enzyme activity and consequently a higher risk of severe toxicities from thiopurines. Our study reports the frequencies of NUDT15 genetic variants in the Slovenian population. We discovered extremely rare genetic variant in the NUDT15 gene, located on chromosome 13 at position 48045861 (GRCh38, NC_000013.11), which did not have a previously assigned rs number. Furthermore, we found that a patient with ALL who had a variant allele NUDT15*3 received a lower dose of thiopurines compared with other patients with the wild-type genotype. This research may help to further understand genetic variations in different populations. Patients treated with thiopurines should have genetic variants in the NUDT15 gene determined. This study further supports the guidelines for dose reduction in patients with variant NUDT15*3 genotype.

The influence of cytotoxic drugs on the immunophenotype of blast cells in paediatric B precursor acute lymphoblastic leukaemia.

BACKGROUND: Flow cytometry plays is important in the diagnosis of acute lymphoblastic leukaemia (ALL) and when antigen-specific immunotherapy is indicated. We have investigated the effects of prednisolone, vincristine, daunorubicin, asparaginase and methotrexate on the antigen expression on blast cells that could influence the planning of antigen-specific therapy as well as risk-based treatment assignment. PATIENTS AND METHODS: Patients aged ≤ 17 years with de novo B-cell ALL (B-ALL) were enrolled in the study. Blast cells were isolated and exposed in vitro to 5 individual cytotoxic drugs in logarithmically increasing concentrations. Then, the expression of CD10, CD19, CD20, CD27, CD34, CD45, CD58, CD66c and CD137 antigens was determined by quantitative flow cytometry. RESULTS: Cytotoxic drugs caused dose-dependent or dose-independent modulation of antigen expression. Daunorubicin caused a dose-dependent down-modulation of CD10, CD19, CD34, CD45 and CD58 and an up-modulation of CD137. Vincristine caused a dose-dependent down-modulation of CD19 and CD58 and an up-modulation of CD45. Daunorubicin also caused dose-independent down-modulation of CD27 and prednisolone down-modulation of CD10, CD19, CD27, CD34 and CD58. Down-modulation of CD20 was detected only in relation to the specific dose of daunorubicin. CONCLUSIONS: The results of the study have shown that cytotoxic drugs can alter the expression of antigens that are important for immunotherapy. Importantly, daunorubicin, prednisolone and vincristine caused down-modulation of CD19 and CD58, suggesting that these drugs are better avoided during bridging therapy prior to bispecific antibodies or CAR-T cell therapy. In addition, immunophenotypic changes on blast cells induced by different drugs could also influence risk-based treatment assignment.

Induction mortality and resource utilization in children treated for acute myeloid leukemia at free-standing pediatric hospitals in the United States.

BACKGROUND: Clinical trials in pediatric acute myeloid leukemia (AML) determine induction regimen standards. However, these studies lack the data necessary to evaluate mortality trends over time and differences in resource utilization between induction regimens. Moreover, these trials likely underreport the clinical toxicities experienced by patients. METHODS: The Pediatric Health Information System database was used to identify children treated for presumed de novo AML between 1999 and 2010. Induction mortality, risk factors for induction mortality, and resource utilization by induction regimen were estimated using standard frequentist statistics, logistic regression, and Poisson regression, respectively. RESULTS: A total of 1686 patients were identified with an overall induction case fatality rate of 5.4% that decreased from 9.8% in 2003 to 2.1% in 2009 (P = .0023). The case fatality rate was 9.0% in the intensively timed DCTER (dexamethasone, cytarabine, thioguanine, etoposide, and rubidomycin [daunomycin]/idarubicin) induction and 3.8% for ADE (cytarabine, daunomycin, and etoposide) induction (adjusted odds ratio = 2.2, 95% confidence interval = 1.1-4.5). Patients treated with intensively timed DCTER regimens had significantly greater antibiotic, red cell/platelet transfusion, analgesic, vasopressor, renal replacement therapy, and radiographic resource utilization than patients treated with ADE regimens. Resource utilization was substantially higher than reported in published pediatric AML clinical trials. CONCLUSIONS: Induction mortality for children with AML decreased significantly as ADE use increased. In addition to higher associated mortality, intensively timed DCTER regimens had a correspondingly higher use of health care resources. Using resource utilization data as a proxy for adverse events, adverse event rates reported on clinical trials substantially underestimated the clinical toxicities of all pediatric AML induction regimens.

Leveraging administrative data to monitor rituximab use in 2875 patients at 42 freestanding children's hospitals across the United States.

OBJECTIVE: To describe the pharmacoepidemiology of rituximab use in children and to estimate the frequency of infectious events within a 1-year period after rituximab exposure. STUDY DESIGN: This is a retrospective cohort study of patients who received rituximab at 1 of 42 children's hospitals contributing data to the Pediatric Health Information System between January 1999 and June 2011. International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) discharge diagnosis codes were analyzed to categorize underlying diseases (hematologic malignancies, primary immunodeficiencies, autoimmune diseases, and transplant recipients) and to estimate inpatient infectious complication rates within each category. RESULTS: A total of 2875 patients with 4639 rituximab admissions were identified. The median age at index admission was 11 years (IQR, 5-15 years). The rate of rituximab admissions increased from 3 to 185 per 100,000 admissions per year over the study interval. During the 1-year follow-up period, 463 patients (16%) died. Infectious events were assessed in 2246 of the rituximab-exposed patients; 6.1% were diagnosed with sepsis and 2.0% with septic shock. The frequency of sepsis ranged from 2.4% in patients with autoimmune diseases to 12.2% in those with primary immunodeficiencies. Three patients were assigned an ICD-9-CM discharge diagnosis code for Pneumocystis joroveci pneumonia, 1 patient was assigned an ICD-9-CM discharge diagnosis code for hepatitis B, and 1 patient was assigned an ICD-9-CM discharge diagnosis code for progressive multifocal leukoencephalopathy. CONCLUSION: The use of rituximab has increased significantly in children with a variety of underlying diseases. Based on ICD-9-CM code data, the rates of sepsis and other life-threatening infections after rituximab exposure vary depending on the underlying condition. Based on surveillance of infection using ICD-9-CM diagnosis codes, the rates of opportunistic infections appear to be low.

Zoonotic infections in pediatric patients with acute leukemia.

Few studies have described the impact of zoonotic diseases in children with leukemia. This study aimed to describe the frequency of and associated demographic factors for zoonotic diseases in pediatric acute leukemia patients. Descriptive and comparative statistics relative to age, sex, and patient region were performed on an assembled 11-year retrospective cohort of acute leukemia patients. Of 10,197 patients, 88 patients (0.86%) were found to have a zoonotic infection. Gastrointestinal diseases were the most commonly (86.4%) identified zoonotic illnesses. Although rare, zoonotic diseases do occur in children with leukemia and frequency varies by age, region, and gender.

Assembly of a cohort of children treated for acute myeloid leukemia at free-standing children's hospitals in the United States using an administrative database.

Pediatric Health Information System data were used to establish a multi-center cohort of 1,686 children treated for newly diagnosed acute myeloid leukemia (AML). The cohort assembly process, which included myeloid leukemia ICD-9 discharge diagnosis codes and manual review of induction chemotherapy, was validated by chart review at a single institution. The use of ICD-9 codes alone resulted in a poor positive predictive value (PPV; 31%). Inclusion of the results from the chemotherapy review improved the PPV to 100% without compromising sensitivity (95.7%). This cohort provides a reliable source for future comparative effectiveness and clinical epidemiology studies in pediatric AML.