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BACKGROUND:Boys with acute lymphoblastic leukemia (ALL) have historically experienced inferior survival compared to girls. This study determined whether sex-based disparities persist with contemporary therapy and whether patterns of treatment failure vary by sex. METHODS:Patients 1 to 30.99 years old were enrolled on frontline Children's Oncology Group trials between 2004 and 2014. Boys received an additional year of maintenance therapy. Sex-based differences in the distribution of various prognosticators, event-free survival (EFS) and overall survival (OS), and subcategories of relapse by site were explored. RESULTS:A total of 8202 (54.4% male) B-cell ALL (B-ALL) and 1562 (74.3% male) T-cell ALL (T-ALL) patients were included. There was no sex-based difference in central nervous system (CNS) status. Boys experienced inferior 5-year EFS and OS (EFS, 84.6% ± 0.5% vs 86.0% ± 0.6%, P = .009; OS, 91.3% ± 0.4% vs 92.5% ± 0.4%, P = .02). This was attributable to boys with B-ALL, who experienced inferior EFS (hazard ratio [HR], 1.2; 95% confidence interval [95% CI], 1.1-1.3; P = .004) and OS (HR, 1.2; 95% CI, 1.0-1.4; P = .046) after adjustment for prognosticators. Inferior B-ALL outcomes in boys were attributable to more relapses (5-year cumulative incidence 11.2% ± 0.5% vs 9.6% ± 0.5%; P = .001), particularly involving the CNS (4.2% ± 0.3% vs 2.5% ± 0.3%; P < .0001). There was no difference in isolated bone marrow relapses (5.4% ± 0.4% vs 6.2% ± 0.4%; P = .49). There were no sex-based differences in EFS or OS in T-ALL. CONCLUSIONS:Sex-based disparities in ALL persist, attributable to increased CNS relapses in boys with B-ALL. Studies of potential mechanisms are warranted. Improved strategies to identify and modify treatment for patients at highest risk of CNS relapse may have particular benefit for boys.

Adolescent and young adult (AYA) patients 16-30 years old with high-risk acute lymphoblastic leukemia (HR-ALL) have inferior outcomes compared to younger HR-ALL patients. AALL0232 was a Phase 3 randomized Children's Oncology Group trial for newly diagnosed HR B-ALL (1-30 years). Between 2004 and 2011, 3154 patients enrolled with 3040 eligible and evaluable for induction. AYA patients comprised 20% of patients (16-21 years, n = 551; 22-30 years, n = 46). 5-year event-free survival and overall survival was 65.4 ± 2.2% and 77.4 ± 2.0% for AYA patients compared to 78.1 ± 0.9% and 87.3 ± 0.7% for younger patients (p < 0.0001). Five-year cumulative incidence of relapse was 18.5 ± 1.7% for AYA patients and 13.5 ± 0.7% for younger patients (p = 0.006), largely due to increased marrow relapses (14.0 ± 1.5% versus 9.1 ± 0.6%; p < 0.0001). Additionally, induction failure rate was higher in AYA (7.2 ± 1.1% versus 3.5 ± 0.4%; p < 0.001) and post-induction remission deaths were significantly higher in AYA (5.7 ± 1.0% versus 2.4 ± 0.3%; p < 0.0001). AALL0232 enrolled the largest number of AYA B-ALL patients to date, demonstrating significantly inferior survival and greater rates of treatment-related toxicities compared to younger patients. Although treatment intensification has improved outcomes in younger patients, they have not been associated with the same degree of improvement for older patients.

[Formula presented] Introduction: Health disparities are major issue for racial, ethnic, and socioeconomically disadvantaged groups. Though outcomes in childhood acute lymphoblastic leukemia (ALL) have steadily improved, identifying persistent disparities is critical. Prior studies evaluating ALL outcomes by race or ethnicity have noted narrowing disparities or that residual disparities are secondary to differences in leukemia biology or socioeconomic status (SES). We aimed to identify persistent inequities by race/ethnicity and SES in childhood ALL in the largest cohort ever assembled for this purpose.
Method(s): We identified a cohort of newly-diagnosed patients with ALL, age 0-30.99 years who were enrolled on COG trials between 2004-2019. Race/ethnicity was categorized as non-Hispanic white vs. Hispanic vs. non-Hispanic Black vs. non-Hispanic Asian vs. Non-Hispanic other. SES was proxied by insurance status: United States (US) Medicaid (public health insurance for low-income individuals) vs. US other (predominantly private insurance) vs. non-US patients (mainly jurisdictions with universal health insurance). Event-free and overall survival (EFS, OS) were compared across race/ethnicity and SES. The relative contribution of disease prognosticators (age, sex, white blood cell count, lineage, central nervous system status, cytogenetics, end Induction minimal residual disease) was examined with Cox proportional hazard multivariable models of different combinations of the three constructs of interest (race/ethnicity, SES, disease prognosticators) and examining hazard ratio (HR) attenuation between models.
Result(s): The study cohort included 24,979 children, adolescents, and young adults with ALL. Non-Hispanic White patients were 13,872 (65.6%) of the cohort, followed by 4,354 (20.6%) Hispanic patients and 1,517 (7.2%) non-Hispanic Black patients. Those insured with US Medicaid were 6,944 (27.8%). Five-year EFS (Table 1) was 87.4%+/-0.3% among non-Hispanic White patients vs. 82.8%+/-0.6% [HR 1.37, 95 ^th confidence interval (95CI) 1.26-1.49; p<0.0001] among Hispanic patients and 81.9%+/-1.2% (HR 1.45, 95CI 1.28-1.56; p<0.0001) among non-Hispanic Black patients. Outcomes for non-Hispanic Asian patients were similar to those of non-Hispanic White patients. US patients on Medicaid had inferior 5-year EFS as compared to other US patients (83.2%+/-0.5% vs. 86.3%+/-0.3%, HR 1.21, 95CI 1.12-1.30; p<0.0001) while non-US patients had the best outcomes (5-year EFS 89.0%+/-0.7%, HR 0.78, 95CI 0.71-0.88; p<0.0001). There was substantial imbalance in traditional disease prognosticators (e.g. T-cell lineage) across both race/ethnicity and SES, and of race/ethnicity by SES. For example, T-lineage ALL accounted for 17.6%, 9.4%, and 6.6% of Non-Hispanic Black, Non-Hispanic White, and Hispanic patients respectively (p<0.0001). Table 2 shows the multivariable models and illustrates different patterns of HR adjustment among specific racial/ethnic and SES groups. Inferior EFS among Hispanic patients was substantially attenuated by the addition of disease prognosticators (HR decreased from 1.37 to 1.17) and further (but not fully) attenuated by the subsequent addition of SES (HR 1.11). In contrast, the increased risk among non-Hispanic Black children was minimally attenuated by both the addition of disease prognosticators and subsequent addition of SES (HR 1.45 to 1.38 to 1.32). Similarly, while the superior EFS of non-US insured patients was substantially attenuated by the addition of race/ethnicity and disease prognosticators (HR 0.79 to 0.94), increased risk among US Medicaid patients was minimally attenuated by the addition of race/ethnicity or disease prognosticators (HR 1.21 to 1.16). OS disparities followed similar patterns but were consistently worse than in EFS, particularly among patients grouped as non-Hispanic other.
Conclusion(s): Substantial disparities in survival outcomes persist by race/ethnicity and SES in the modern era. Our findings suggest that reasons for these disparities vary between specific disadvantaged groups. Additional work is required to identify specific drivers of survival disparities that may be mitigated by targeted interventions. [Formula presented] Disclosures: Gupta: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Teachey: NeoImmune Tech: Research Funding; Sobi: Consultancy; BEAM Therapeutics: Consultancy, Research Funding; Janssen: Consultancy. Zweidler-McKay: ImmunoGen: Current Employment. Loh: MediSix therapeutics: Membership on an entity's Board of Directors or advisory committees.
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Background Acute Lymphoblastic Leukemia (ALL) is the most common pediatric cancer and while curable in the majority of cases, 15%-20% of children will relapse with only 50% surviving long-term. Treatment failures arise from the outgrowth of pre-existing or acquired sub-clones that are genetically or epigenetically primed to resist treatment. In addition, the bone marrow microenvironment is known to provide a protective niche. We performed the first mapping of the human B-cell ALL (B-ALL) immune bone marrow (BM) microenvironment at single cell resolution at diagnosis, remission and relapse (Witkowski, 2020). We uncovered a striking rewiring of the myeloid compartment during B-ALL progression with significant over-representation of a leukemia-associated monocyte subpopulation expressing high levels of the Macrophage Colony Stimulating Factor Receptor (M-CSFR/CSF1R). Using both peripheral blood (PB) complete blood count analysis and RNA-seq data, we demonstrated that high monocyte abundance at B-ALL diagnosis is predictive of inferior pediatric and adult overall survival in two large independent clinical cohorts. To determine the association of non-classical monocyte abundance in BM and PB with risk of relapse, we examined a cohort of clinical samples from children enrolled on Children's Oncology Group (COG) protocols. Methods Using an unmatched case-control design, we established a preliminary cohort of PB and BM samples collected at diagnosis from 24 B-ALL patients with eventual relapse and 24 patients in long-term remission. Four remission samples from an NYU Langone cohort were used to validate the expansion of this population in the presence of B-ALL. We applied a customized flow cytometry based assay to identify CD115-expressing human monocyte subsets: classical (CD45 ⁺CD56 ^-CD14 ⁺CD16 ^-), non-classical (CD45 ⁺CD56 ^-CD14 ^-CD16 ⁺), as well as B-cells (CD19, CD22, CD10) and T/NK cells (CD3, CD56). We then performed univariate and multivariable analysis of outcome (relapse versus long-term remission) compared to monocyte subset abundance, adjusting for potential confounding factors (age, gender, CNS status, NCI risk, genetic subtype, WBC at diagnosis, and end of induction minimal residual disease). Results We observed a significantly higher percentage of non-classical monocytes in the diagnostic BM from the COG cohort when compared to remission samples (COG diagnostic B-ALL BM non-classical percentage mean 52.19% vs NYU B-ALL remission BM non-classical percentage mean 1.775%, P = 0.0001). We also observed a strong correlation between the percentage of non-classical monocytes in the PB when compared to their matched BM specimens (r = 0.6, P = 0.0001). Multivariable analysis revealed a significant association between PB non-classical monocyte percentage at diagnosis and patient outcome (remission cohort non-classical monocyte percentage [mean, range]: 52.4%, 33.3-68.1%, n = 24, relapse cohort non-classical monocyte percentage: 65.9%, 56.4-84.7%, n = 24, P = 0.021). Similarly, a strong trend was observed in the BM, although it did not reach statistical significance. Flow cytometric analysis confirmed CD115 (M-CSFR/CSF1R) expression in this non-classical monocyte population, thereby validating a novel target for intervention. Conclusions These findings validate the presence of a unique monocyte subpopulation associated with childhood B-ALL and suggests that assessing this population in PB at diagnosis may be of prognostic significance. The availability of small molecule inhibitors and monoclonal antibodies targeting CSF1R-expressing monocytes may offer a novel approach to treating B-ALL. [Formula presented] Disclosures: Raetz: Pfizer: Research Funding; Celgene: Other: DSMB member. Teachey: Sobi: Consultancy; NeoImmune Tech: Research Funding; Janssen: Consultancy; BEAM Therapeutics: Consultancy, Research Funding. Aifantis: AstraZeneca: Research Funding; Foresite (FL2020-010) LLC: Consultancy.
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We conducted the first HLA allele and genome wide association study to identify loci associated with hypersensitivity reactions exclusively to the PEGylated preparation of asparaginase (pegaspargase) in racially diverse cohorts of pediatric leukemia patients: St. Jude Children's Research Hospital's Total XVI (TXVI, n = 598), Children's Oncology Group AALL0232 (n = 2472) and AALL0434 (n = 1189). Germline DNA was genotyped using arrays. Genetic variants not genotyped directly were imputed. HLA alleles were imputed using SNP2HLA or inferred using BWAkit. Analyses between genetic variants and hypersensitivity were performed in each cohort first using cohort-specific covariates and then combined using meta-analyses. Nongenetic risk factors included fewer intrathecal injections (P = 2.7x10^-5 in TXVI) and male sex (P = 0.025 in AALL0232). HLA alleles DQB1*02:02, DRB1*07:01, and DQA1*02:01 had the strongest associations with pegaspargase hypersensitivity (P < 5.0x10^-5 ) in patients with primarily European ancestry (EA), with the three alleles associating in a single haplotype. The top allele HLA-DQB1*02:02 was tagged by HLA-DQB1 rs1694129 in EAs (r² = 0.96) and less so in non-EAs. All single nucleotide polymorphisms associated with pegaspargase hypersensitivity reaching genome-wide significance in EAs were in class II HLA loci, and were partially replicated in non-EAs, as is true for other HLA associations. The rs9958628 variant, in ARHGAP28 (previously linked to immune response in children) had the strongest genetic association (P = 8.9x10^-9 ) in non-EAs. The HLA-DQB1*02:02-DRB1*07:01-DQA1*02:01 associated with hypersensitivity reactions to pegaspargase is the same haplotype associated with reactions to non-PEGylated asparaginase, even though the antigens differ between the two preparations.

Early T-cell precursor phenotype acute lymphoblastic leukemia (ETP-ALL) is a subtype of T-ALL with a unique immunophenotype and genetic abnormalities distinct from conventional T-ALL. A subset of T lymphoblastic lymphoma (T-LLy) also demonstrates the early T-cell precursor immunophenotype and may be a counterpart of ETP-ALL. Unlike ETP-ALL, the incidence, clinical features, and genomic features of ETP-LLy are unknown. We reviewed the immunophenotyping data of 218 T-LLy patients who enrolled in the Children's Oncology Group AALL0434 clinical trial and identified 9 cases (4%) exhibiting a definitive ETP immunophenotype. We performed single-nucleotide polymorphism array profiling on 9 ETP-LLy and 15 non-ETP T-LLy cases. Compared with non-ETP T-LLy, ETP-LLy showed less frequent deletion of 9p (CKDN2A/B), more frequent deletion of 12p (ETV6) and 1p (RPL22), and more frequent absence of biallelic T-cell receptor γ deletions. Recurrent abnormalities previously described in ETP-ALL such as deletions of 5q and 13q and gain of 6q were not observed in ETP-LLy cases. There were no failures of therapy among the ETP-LLy subtype with a 4-year event-free survival of 100%. Overall, ETP-LLy does not exhibit unifying genetic alterations but shows some distinct genomic features from non-ETP T-LLy suggesting that ETP-LLy may be a distinct entity from non-ETP T-LLy.