Surgical aspects and outcomes after nephrectomy for Wilms tumour in sub-Saharan Africa: A report from Wilms Africa Phase II-CANCaRe Africa.

BACKGROUND: Wilms tumour (WT) is one of the common and curable cancer types targeted by the Global Initiative for Childhood Cancer. Tumour excision is essential for cure. This analysis focuses on surgical outcomes of patients with WT in sub-Saharan Africa. METHODS: We implemented a risk-stratified WT treatment guideline as a multicentre, prospective study across eight hospitals and six countries. Eligibility criteria were age 6 months to 16 years, unilateral WT, surgery performed after preoperative chemotherapy and diagnosed between 1 January 2021 and 31 December 2022. Data collection included a specific surgical case report form (CRF). RESULTS: The study registered 230 patients, among whom 164 (71.3%) had a nephrectomy. Ninety-eight percent of patients had a completed surgical CRF. Out 164 patients, 50 (30.5%) had distant metastases. Median tumour diameter at surgery was 11.0 cm. Lymph node sampling was done in 122 (74.3%) patients, 34 (20.7%) had intraoperative tumour rupture, and for 18 (10.9%), tumour resection involved en bloc resection of another organ. Tumour size at surgery was significantly correlated with tumour rupture (p < .01). With a median follow-up of 17 months (range: 2-33), 23 (14.0%) patients have relapsed. Twenty-two (13.4%) patients abandoned treatment post nephrectomy. Two-year event-free survival was 60.4% ± 4.7% with treatment abandonment as an event. CONCLUSION: Survival post nephrectomy is challenged by treatment abandonment, treatment-related mortality and relapse. Large tumours after preoperative chemotherapy were associated with a higher risk of tumour rupture. Earlier diagnosis and access to radiotherapy are expected to improve survival.

Prevention of treatment abandonment remains an important challenge to increase survival of Wilms tumor in sub-Saharan Africa: A report from Wilms Africa-CANCaRe Africa.

BACKGROUND: The Wilms Africa studies implemented an adapted Wilm's tumor (WT) treatment protocol in sub-Saharan Africa in two phases. Phase I began with four sites and provided out-of-pocket costs. Phase II expanded the number of sites, but lost funding provision. Objective is to describe the outcomes of Phase II and compare with Phase I. METHODS: Wilms Africa Phase I (n = 4 sites; 2014-2018) and Phase II (n = 8 sites; 2021-2022) used adapted treatment protocols. Funding for families' out-of-pocket costs was provided during Phase I but not Phase II. Eligibility criteria were age less than 16 years and newly diagnosed unilateral WT. We documented patients' outcome at the end of planned first-line treatment categorized as treatment abandonment, death during treatment, and disease-related events (death before treatment, persistent disease, relapse, or progressive disease). Sensitivity analysis compared outcomes in the same four sites. RESULTS: We included 431 patients in Phase I (n = 201) and Phase II (n = 230). The proportion alive without evidence of disease decreased from 69% in Phase I to 54% in Phase II at all sites (p = .002) and 58% at the original four sites (p = .04). Treatment abandonment increased overall from 12% to 26% (p < .001), and was 20% (p = .04) at the original four sites. Disease-related events (5% vs. 6% vs. 6%) and deaths during treatment (14% vs. 14% vs. 17%) were similar. CONCLUSION: Provision of out-of-pocket costs was important to improve patient outcomes at the end of planned first-line treatment in WT. Prevention of treatment abandonment remains an important challenge.

Human leukocyte antigen-DQA1*04:01 and rs2040406 variants are associated with elevated risk of childhood Burkitt lymphoma.

Burkitt lymphoma (BL) is responsible for many childhood cancers in sub-Saharan Africa, where it is linked to recurrent or chronic infection by Epstein-Barr virus or Plasmodium falciparum. However, whether human leukocyte antigen (HLA) polymorphisms, which regulate immune response, are associated with BL has not been well investigated, which limits our understanding of BL etiology. Here we investigate this association among 4,645 children aged 0-15 years, 800 with BL, enrolled in Uganda, Tanzania, Kenya, and Malawi. HLA alleles are imputed with accuracy >90% for HLA class I and 85-89% for class II alleles. BL risk is elevated with HLA-DQA1*04:01 (adjusted odds ratio [OR] = 1.61, 95% confidence interval [CI] = 1.32-1.97, P = 3.71 × 10-6), with rs2040406(G) in HLA-DQA1 region (OR = 1.43, 95% CI = 1.26-1.63, P = 4.62 × 10-8), and with amino acid Gln at position 53 versus other variants in HLA-DQA1 (OR = 1.36, P = 2.06 × 10-6). The associations with HLA-DQA1*04:01 (OR = 1.29, P = 0.03) and rs2040406(G) (OR = 1.68, P = 0.019) persist in mutually adjusted models. The higher risk rs2040406(G) variant for BL is associated with decreased HLA-DQB1 expression in eQTLs in EBV transformed lymphocytes. Our results support the role of HLA variation in the etiology of BL and suggest that a promising area of research might be understanding the link between HLA variation and EBV control.

Sickle cell allele HBB-rs334(T) is associated with decreased risk of childhood Burkitt lymphoma in East Africa.

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that significantly contributes to childhood cancer burden in sub-Saharan Africa. Plasmodium falciparum, which causes malaria, is geographically associated with BL, but the evidence remains insufficient for causal inference. Inference could be strengthened by demonstrating that mendelian genes known to protect against malaria-such as the sickle cell trait variant, HBB-rs334(T)-also protect against BL. We investigated this hypothesis among 800 BL cases and 3845 controls in four East African countries using genome-scan data to detect polymorphisms in 22 genes known to affect malaria risk. We fit generalized linear mixed models to estimate odds ratios (OR) and 95% confidence intervals (95% CI), controlling for age, sex, country, and ancestry. The ORs of the loci with BL and P. falciparum infection among controls were correlated (Spearman's ρ = 0.37, p = .039). HBB-rs334(T) was associated with lower P. falciparum infection risk among controls (OR = 0.752, 95% CI 0.628-0.9; p = .00189) and BL risk (OR = 0.687, 95% CI 0.533-0.885; p = .0037). ABO-rs8176703(T) was associated with decreased risk of BL (OR = 0.591, 95% CI 0.379-0.992; p = .00271), but not of P. falciparum infection. Our results increase support for the etiological correlation between P. falciparum and BL risk.

Mosaic chromosomal alterations in peripheral blood leukocytes of children in sub-Saharan Africa.

In high-income countries, mosaic chromosomal alterations in peripheral blood leukocytes are associated with an elevated risk of adverse health outcomes, including hematologic malignancies. We investigate mosaic chromosomal alterations in sub-Saharan Africa among 931 children with Burkitt lymphoma, an aggressive lymphoma commonly characterized by immunoglobulin-MYC chromosomal rearrangements, 3822 Burkitt lymphoma-free children, and 674 cancer-free men from Ghana. We find autosomal and X chromosome mosaic chromosomal alterations in 3.4% and 1.7% of Burkitt lymphoma-free children, and 8.4% and 3.7% of children with Burkitt lymphoma (P-values = 5.7×10-11 and 3.74×10-2, respectively). Autosomal mosaic chromosomal alterations are detected in 14.0% of Ghanaian men and increase with age. Mosaic chromosomal alterations in Burkitt lymphoma cases include gains on chromosomes 1q and 8, the latter spanning MYC, while mosaic chromosomal alterations in Burkitt lymphoma-free children include copy-neutral loss of heterozygosity on chromosomes 10, 14, and 16. Our results highlight mosaic chromosomal alterations in sub-Saharan African populations as a promising area of research.

IFNL4 Genotypes and Risk of Childhood Burkitt Lymphoma in East Africa.

Interferon lambda 4 (IFN-λ4) is a novel type-III interferon that can be expressed only by carriers of the genetic variant rs368234815-dG within the first exon of the IFNL4 gene. Genetic inability to produce IFN-λ4 (in carriers of the rs368234815-TT/TT genotype) has been associated with improved clearance of hepatitis C virus (HCV) infection. The IFN-λ4-expressing rs368234815-dG allele (IFNL4-dG) is most common (up to 78%) in West sub-Saharan Africa (SSA), compared to 35% of Europeans and 5% of individuals from East Asia. The negative selection of IFNL4-dG outside Africa suggests that its retention in African populations could provide survival benefits, most likely in children. To explore this hypothesis, we conducted a comprehensive association analysis between IFNL4 genotypes and the risk of childhood Burkitt lymphoma (BL), a lethal infection-associated cancer most common in SSA. We used genetic, epidemiologic, and clinical data for 4,038 children from the Epidemiology of Burkitt Lymphoma in East African Children and Minors (EMBLEM) and the Malawi Infections and Childhood Cancer case-control studies. Generalized linear mixed models fit with the logit link controlling for age, sex, country, P. falciparum infection status, population stratification, and relatedness found no significant association between BL risk and 3 coding genetic variants within IFNL4 (rs368234815, rs117648444, and rs142981501) and their combinations. Because BL occurs in children 6-9 years of age who survived early childhood infections, our results suggest that additional studies should explore the associations of IFNL4-dG allele in younger children. This comprehensive study represents an important baseline in defining the health effects of IFN-λ4 in African populations.

Towards zero percent treatment abandonment of patients with common and curable childhood cancer types in Blantyre, Malawi.

BACKGROUND: Treatment abandonment is a common cause of treatment failure in low-income countries (LIC). We implemented a comprehensive package of interventions aiming to enable all families to complete the treatment of their child. The objective of this study was to evaluate the impact of those interventions. PROCEDURE: In this prospective and historically controlled study, we included all children younger than 16 years with a newly diagnosed common and curable cancer type (acute lymphoblastic leukaemia [ALL], Hodgkin disease, Wilms tumour, retinoblastoma and Burkitt lymphoma) admitted to the Queen Elizabeth Central Hospital in Blantyre, Malawi, between 1 June 1 2019 and 1 June 1 2020. Interventions to enable treatment completion included full funding of costs to the family (treatment, transport, accommodation and food in the hospital) and tracking of patients if they did not attend treatment appointments. The outcomes of patients were compared with those of a similar historical cohort. RESULTS: The intervention cohort of 150 patients were compared to 264 historical control patients. Treatment abandonment decreased significantly from 19% (49/264) to 7% (10/150) (p < .001). The proportion of patients with Wilms tumour, retinoblastoma or ALL alive without evidence of disease at the end of treatment increased from 38% (57/149) to 53% (44/83) (p = .03). CONCLUSION: A simple and relatively low-cost comprehensive intervention package with no costs for families, significantly decreased treatment abandonment. This strategy may increase survival of children with common and curable cancers in LIC, especially when coupled with improvements in access to treatment and quality of treatment, including supportive care.

Treatment abandonment: A report from the collaborative African network for childhood cancer care and research-CANCaRe Africa.

BACKGROUND: 'Treatmentabandonment' is a common and preventable cause of childhood cancer treatment failure in low- and middle-income countries (LMIC). Risk factors and effective interventions in LMIC are reported. Poverty and costs of treatment are perceived as overriding causes in sub-Saharan Africa. The objective of this study was to study potential determinants of treatment abandonment, including aspects of treatment costs in sub-Saharan Africa, to be better informed for planned future interventions. METHODS: A multicentre, prospective, observational, cohort study was conducted in five hospitals in sub-Saharan Africa. Children younger than 16 years with newly diagnosed cancer treated as inpatient with curative intent were included. The occurrence of treatment abandonment and potential determinants including aspects of treatment costs were documented during the first 3 months of treatment. RESULTS: We included 252 patients (median age 6.0, range 0.2-15.0 years, 54% male). The most common cancer was Burkitt lymphoma (63/252, 25%). Seven percent of patients (18 of 252) abandoned treatment. Two thirds (65%, 163/252) of patients had to borrow money to reach the hospital for the diagnosis and start of treatment. Treatment abandonment occurred more frequently in families who had to borrow money (16/163, 10%) versus those who did not (2/89, 2%; p = .026). CONCLUSIONS: Limiting costs for families and improved counselling may reduce treatment abandonment. Development and implementation of interventions to reduce treatment abandonment are required in sub-Saharan Africa.

Fever and neutropenia outcomes and areas for intervention: A report from SUCCOUR - Supportive Care for Children with Cancer in Africa.

BACKGROUND: Death during paediatric cancer treatment is common in sub-Saharan Africa. Using the infrastructure of Supportive Care for Children with Cancer in Africa (SUCCOUR), our objective was to describe fever and neutropenia (FN) characteristics and outcomes in order to identify potential areas for future intervention. METHODS: A multicentre prospective, observational cohort study was conducted in sub-Saharan Africa. Data were collected from September 2019 to March 2020. Children below 16 years with newly diagnosed cancer treated with curative intent were included. Data were abstracted in real time using standardised case report forms by trained personnel. Characteristics and outcomes of FN during the first 3 months of treatment were documented. RESULTS: A total of 252 patients were included (median age 6.0, range 0.2-15.0 years, 54% male). The most common cancer was Burkitt lymphoma (63/252, 25%). Among 104 FN episodes, 21 (21%) were associated with prolonged neutropenia (>1 week) and 32 (31%) were associated with profound neutropenia (absolute neutrophil count <0.1 × 109 /L). In 10/104 (10%) episodes, empiric antibiotics were started within 1 hour following fever onset and in 16/104 (15%) episodes, a blood culture was obtained before starting antibiotics. Malaria parasitaemia was detected in four of 104 (4%). A total of 11/104 (11%) patients died in the FN episodes. CONCLUSIONS: Although in most, FN was not associated with prolonged or profound neutropenia, 11% resulted in death. Areas to target include blood cultures prior to antibiotics and earlier initiation of empiric antibiotics. Future efforts should modify FN practices to reduce treatment-related mortality.

Early death and treatment-related mortality: A report from SUCCOUR - Supportive Care for Children with Cancer in Africa.

BACKGROUND: Deaths during paediatric cancer treatment are common in Africa. It is often difficult to distinguish between treatment-related and disease-related causes. To prevent these deaths, it is important to study them and identify the cause. The Supportive Care for Children with Cancer in Africa (SUCCOUR) programme enabled a study with the objective to identify the reasons for early death during treatment. METHODS: We conducted a multicentre prospective, observational cohort study in sub-Saharan Africa. Children younger than 16 years with newly diagnosed cancer treated with curative intent were included from 1 September 2019 until 30 March 2020. Data were abstracted in real time by trained personnel using standardised case report forms. The treating clinician's assessment of the cause of death and signs, symptoms and laboratory values of patients who died during the first 3 months of treatment (early death) were documented. RESULTS: We included 252 patients (median age 6.0, range 0.2-15.0 years, 54% male). The most common cancer was Burkitt lymphoma (63/252, 25%). Fifteen percent of patients (37/252) died during the first 3 months of treatment. Of these 37 patients, 33 (89%) died of a treatment-related cause. Treatment-related mortality of all patients in the first 3 months of treatment was 13% (33/252). CONCLUSION: Fifteen percent of patients had an early death during treatment and 13% had a treatment-related death. This suggests the need to improve supportive care. Implementation of supportive care pathways adapted to local circumstances may be helpful.

Transfusion management of severe anaemia in African children: a consensus algorithm.

The phase III Transfusion and Treatment of severe anaemia in African Children Trial (TRACT) found that conservative management of uncomplicated severe anaemia [haemoglobin (Hb) 40-60 g/l] was safe, and that transfusion volume (20 vs. 30 ml/kg whole blood equivalent) for children with severe anaemia (Hb <60 g/l) had strong but opposing effects on mortality, depending on fever status (>37·5°C). In 2020 a stakeholder meeting of paediatric and blood transfusion groups from Africa reviewed the results and additional analyses. Among all 3196 children receiving an initial transfusion there was no evidence that nutritional status, presence of shock, malaria parasite burden or sickle cell disease status influenced outcomes or modified the interaction with fever status on volume required. Fever status at the time of ordering blood was a reliable determinant of volume required for optimal outcome. Elevated heart and respiratory rates normalised irrespective of transfusion volume and without diuretics. By consensus, a transfusion management algorithm was developed, incorporating three additional measurements of Hb post-admission, alongside clinical monitoring. The proposed algorithm should help clinicians safely implement findings from TRACT. Further research should assess its implementation in routine clinical practice.

Assessment of Mixed Plasmodium falciparum sera5 Infection in Endemic Burkitt Lymphoma: A Case-Control Study in Malawi.

BACKGROUND: Endemic Burkitt lymphoma (eBL) is the most common childhood cancer in Africa and is linked to Plasmodium falciparum (Pf) malaria infection, one of the most common and deadly childhood infections in Africa; however, the role of Pf genetic diversity is unclear. A potential role of Pf genetic diversity in eBL has been suggested by a correlation of age-specific patterns of eBL with the complexity of Pf infection in Ghana, Uganda, and Tanzania, as well as a finding of significantly higher Pf genetic diversity, based on a sensitive molecular barcode assay, in eBL cases than matched controls in Malawi. We examined this hypothesis by measuring diversity in Pf-serine repeat antigen-5 (Pfsera5), an antigenic target of blood-stage immunity to malaria, among 200 eBL cases and 140 controls, all Pf polymerase chain reaction (PCR)-positive, in Malawi. METHODS: We performed Pfsera5 PCR and sequencing (~3.3 kb over exons II-IV) to determine single or mixed PfSERA5 infection status. The patterns of Pfsera5 PCR positivity, mixed infection, sequence variants, and haplotypes among eBL cases, controls, and combined/pooled were analyzed using frequency tables. The association of mixed Pfsera5 infection with eBL was evaluated using logistic regression, controlling for age, sex, and previously measured Pf genetic diversity. RESULTS: Pfsera5 PCR was positive in 108 eBL cases and 70 controls. Mixed PfSERA5 infection was detected in 41.7% of eBL cases versus 24.3% of controls; the odds ratio (OR) was 2.18, and the 95% confidence interval (CI) was 1.12-4.26, which remained significant in adjusted results (adjusted odds ratio [aOR] of 2.40, 95% CI of 1.11-5.17). A total of 29 nucleotide variations and 96 haplotypes were identified, but these were unrelated to eBL. CONCLUSIONS: Our results increase the evidence supporting the hypothesis that infection with mixed Pf infection is increased with eBL and suggest that measuring Pf genetic diversity may provide new insights into the role of Pf infection in eBL.

Early doxorubicin cardiotoxicity in Malawian children admitted to Queen Elizabeth Central Hospital, Malawi.

BACKGROUND: Doxorubicin is known to cause chemotherapy-induced cardiotoxicity. In resource-poor settings, monitoring for cardiotoxicity is not routinely done, and its incidence is unknown. The aim of this study was to determine the proportion of children who developed doxorubicin-induced cardiotoxicity within 1 year of having received treatment at paediatric oncology ward. METHODS: Children aged 3 months to 18 years with cancer were prospectively enrolled and followed up between January 2016 to June 2019. Transthoracic echocardiogram was done at baseline, 1 month, 6 months and a year after completion of therapy. Cardiotoxicity was defined as a decline in left ventricular ejection fraction (LVEF) of ≥10% to a final value of <50%. An overall incidence risk of developing cardiotoxicity was estimated. A one-way analysis of variance (ANOVA) was conducted to compare baseline LVEF with follow-up measurements. FINDINGS: Ninety-one children were enrolled, 74% (68/91) were male, and 67% (62/91) were aged 5 months to 14 years. Most patients received a doxorubicin cumulative dose between 100 and 200 mg/m2 and no cardiotoxicity was observed during the study period. However, of 77 children with at least one follow up, five children 6.54% (95% CI: 2.1-14.5) experienced LVEF reduction of >10%, though not to a final value of <50%. No deterioration of systolic function was found among 20 children who completed follow-up (F = 2.43, p-value = .07). INTERPRETATION: In this cohort of patients, most received a low cumulative doxorubicin dose and only 22% were available for evaluation at study end; no cardiotoxic events associated with doxorubicin administration were observed after 12 months.

Outcome at the end of treatment of patients with common and curable childhood cancer types in Blantyre, Malawi.

BACKGROUND: The WHO Global Initiative for Childhood Cancer aims to increase survival to at least 60% for all children with cancer globally, with initial focus on six common curable cancer types. Frequent causes of treatment failure in low income countries (LICs) are treatment abandonment and death during treatment. Here, we report on the outcome at the end of treatment of patients with newly diagnosed common and curable cancer types, admitted in the Queen Elizabeth Central Hospital, Blantyre, Malawi. PROCEDURE: Outcome at end of treatment was documented and analyzed retrospectively for all children with a working diagnosis of a common and curable cancer type (ALL, Hodgkin disease, Wilms tumor, retinoblastoma, and Burkitt lymphoma) admitted over a 2-year period. Patients with a misdiagnosis were excluded. Outcomes were categorized as alive without evidence of disease, treatment abandonment, death during treatment, or persistent disease. RESULTS: We included 264 patients. Seven patients with a misdiagnosis were excluded. At the end of treatment, 53% (139 of 264) of patients were alive without evidence of disease, 19% (49 of 264) had abandoned treatment, 23% (61 of 264) had died during treatment, and 6% (15 of 264) had persistent disease. CONCLUSION: Survival of children with common and curable cancers is (significantly) below 50%. Almost half (42%) of the patients either abandoned treatment or died during treatment. Strategies to enable parents to complete treatment of their child and improved supportive care are needed. Such interventions may need to be given priority to improve the currently poor survival.

Improvement of overall survival in the Collaborative Wilms Tumour Africa Project.

INTRODUCTION: The Collaborative Wilms Tumour (WT) Africa Project implemented an adapted WT treatment guideline in six centres in sub-Saharan Africa. The primary objectives were to describe abandonment of treatment, death during treatment, event-free survival (EFS) and relapse following implementation. An exploratory objective was to compare outcomes with the baseline evaluation, a historical cohort preceding implementation. METHODS: The Collaborative WT Africa Project is a multi-centre prospective clinical trial that began in 2014. Funding was distributed to all participating centres and used to cover treatment, travel and other associated costs for patients. Patient characteristics, tumour characteristics and events were described. RESULTS: In total, 201 WT patients were included. Two-year EFS was 49.9 ± 3.8% when abandonment of treatment was considered an event. Relapse of disease occurred in 21% (42 of 201) of all included patients and in 26% (42 of 161) of those who had a nephrectomy. Programme implementation was associated with significantly higher survival without evidence of disease at the end of treatment (52% vs 68.5%, P = .002), significantly reduced abandonment of treatment (23% vs 12%, P = .009) and fewer deaths during treatment (21% vs 13%, P = .06). CONCLUSION: This collaborative implementation of an adapted WT treatment guideline, using relatively simple and low-cost interventions, was feasible. Two-year EFS was almost 50%. In addition, a significant decrease in treatment abandonment and an increase in survival at the end of treatment were observed compared to a pre-implementation cohort. Future work should focus on decreasing deaths during treatment and will include enhancing supportive care.

Highlights from the 13th African Continental Meeting of the International Society of Paediatric Oncology (SIOP), 6-9 March 2019, Cairo, Egypt.

The 13th African continental meeting of the international society of paediatric oncology, held on 6-9 March 2019 in Cairo, was organised in collaboration with the Children Cancer Hospital (57357) in Egypt and the global parents' organisation (Childhood Cancer International) and supported by a large international faculty. With 629 delegates from 37 countries (24 African), this was the largest forum of healthcare professionals focused on children and young people with cancer in Africa to showcase advances and discuss further improvements. Three targeted workshops, on nursing care, pharmacy and nutrition, attracted large numbers and catalysed new collaborative initiatives in supportive care studies, extended roles for pharmacists in quality control and care delivery and addressed malnutrition concurrently with cancer treatment. The Collaborative Wilms Tumour Africa Project, open in seven sub-Saharan countries, and the trials in Burkitt's lymphoma reported encouraging outcomes with further initiatives in supportive care (the supportive care for children with cancer in Africa project). While acknowledging deficits in radiotherapy provision, available in only 23 of 52 African countries, centres with facilities reported their technical advances that benefit patients. Of great importance for children with brain tumours, who are underdiagnosed in Africa, was the first announcement of African paediatric neuro-oncology society, whose 63 current members aim to tackle the shortage of neurosurgeons through training fellowships, workshops and a dedicated conference. The congress provided the opportunity to discuss how African countries will work with the WHO global initiative aiming to improve childhood cancer survival to 60% in all countries by 2030. This conference report is dedicated to the three Kenyan delegates who died tragically on the Ethiopian Airlines flight ET302 on their way home, full of new ideas and pride in what they had achieved so far. All those who heard their presentations are determined to continue their excellent work to improve cancer care for children in Africa.

Sporadic and endemic Burkitt lymphoma have frequent FOXO1 mutations but distinct hotspots in the AKT recognition motif.

FOXO1 has an oncogenic role in adult germinal center-derived lymphomas, in which mutations, predominately within the AKT recognition motif, cause nuclear retention of FOXO1, resulting in increased cell proliferation. To determine the prevalence and distribution of FOXO1 mutations in pediatric Burkitt lymphoma (BL), we sequenced a large number of sporadic and endemic BL patient samples. We report a high frequency of FOXO1 mutations in both sporadic and endemic BL at diagnosis, occurring in 23/78 (29%) and 48/89 (54%) samples, respectively, as well as 8/16 (50%) cases at relapse. Mutations of T24 were the most common in sporadic BL but were rare in endemic cases, in which mutations of residue S22, also within the AKT recognition motif, were the most frequent. FOXO1 mutations were almost always present in the major tumor cell clone but were not associated with outcome. Analysis of other recurrent mutations reported in BL revealed that FOXO1 mutations were associated with mutations of DDX3X and ARID1A, but not MYC, TCF3/ID3, or members of the phosphatidylinositol 3-kinase signaling pathway. We further show common nuclear retention of the FOXO1 protein, irrespective of mutation status, suggesting alternative unknown mechanisms for maintaining FOXO1 transcriptional activity in BL. CRISPR/Cas9 knockout of FOXO1 in an endemic cell line produced a significant decrease in cell proliferation, supporting an oncogenic role for FOXO1 in endemic BL. Thus, FOXO1 is frequently mutated in both sporadic and endemic BL and may offer a potential therapeutic target for pediatric BL patients worldwide.