Evaluation of prevalence and outcomes of serial tyrosine kinase inhibitor use in pediatric patients with advanced solid tumors.

PURPOSE: Multitargeted tyrosine kinase inhibitors (mTKIs) are increasingly utilized in the treatment of pediatric sarcomas and other solid tumors. It is unknown whether serial treatment with multiple TKIs provides a benefit and which patients are most likely to benefit from mTKI rechallenge. METHODS: We performed a retrospective cohort study of pediatric cancer patients who received serial mTKI therapy off-study between 2007 and 2020 as either monotherapy or combination therapy. We report patient characteristics, clinical outcomes, dosing patterns, and treatment-associated toxicity. RESULTS: The study cohort included 25 patients. The overall prevalence of serial mTKI therapy among all patients treated for sarcoma at our institution was 3.7%, and the response rate to second mTKI was 9%. Median 6-month progression-free survival (PFS) and overall survival (OS) from start of second mTKI were 42.1% (95% CI: 20.4%-62.5%) and 79.1% (95% CI: 57.0%-90.8%), respectively. Patients who had received 4 months or more (n = 11) of therapy with first mTKI had significantly longer PFS versus those who received less than 4 months (n = 11; p = .001). Thirty-three percent of patients discontinued second mTKI due to toxicity. Six (40%) of 15 patients who discontinued the first mTKI due to progression had either a partial response or stable disease on the second mTKI. CONCLUSIONS: We observed a low response rate to mTKI rechallenge. However, we identified patients who had been treated with first mTKI for  ≥4 months as more likely to have prolonged stable disease with second mTKI. Several patients had a response or stable disease on the second mTKI despite having progressed on the first mTKI. Though toxicity was common, only a minority of patients discontinued the second mTKI due to toxicity.

Phase 1 study of cabozantinib in combination with topotecan-cyclophosphamide for patients with relapsed Ewing sarcoma or osteosarcoma.

PURPOSE: Phase 1 study assessing the safety and toxicity of cabozantinib in combination with topotecan and cyclophosphamide for relapsed osteosarcoma and Ewing sarcoma. METHODS: Oral cabozantinib (25 mg/m2 ) was administered daily for 21 (dose level 1) or 14 (dose level -1B) days. Topotecan (0.75 mg/m2 ) and cyclophosphamide (250 mg/m2 ) were administered intravenously (IV) on days 1-5. A modified 3+3 design based upon first cycle dose-limiting toxicities (DLT) was used for dose escalation. RESULTS: Twelve patients with a median age of 15 (12.9-33.2) years were enrolled (seven with Ewing sarcoma; five with osteosarcoma); all were evaluable for toxicity. At dose level 1, three of six patients developed first cycle DLT: grade 3 epistaxis, grade 3 transaminitis, and prolonged grade 2 thrombocytopenia. Six patients were enrolled on dose level -1B (interrupted cabozantinib, given days 8-21), with one first cycle DLT (grade 3 pneumothorax) observed. Of the 10 response evaluable patients, one had partial response (Ewing sarcoma), seven had stable disease, and two had progressive disease. CONCLUSIONS: The recommended phase 2 doses and schedules for this combination are topotecan 0.75 mg/m2 IV days 1-5, cyclophosphamide 250 mg/m2 IV days 1-5, and cabozantinib 25 mg/m2 days 8-21. Non-concomitant administration of cabozantinib with cytotoxic therapy in this population has acceptable toxicity, while allowing for potential disease control.

Adverse prognostic impact of the loss of STAG2 protein expression in patients with newly diagnosed localised Ewing sarcoma: A report from the Children's Oncology Group.

BACKGROUND: Ewing sarcoma (EWS) is an aggressive sarcoma with no validated molecular biomarkers. We aimed to determine the frequency of STAG2 protein loss by immunohistochemistry (IHC) and whether loss of expression is associated with outcome. METHODS: We performed a retrospective cohort study of patients with EWS enrolled to Children's Oncology Group studies. We obtained unstained slides from 235 patients and DNA for sequencing from 75 patients. STAG2 expression was tested for association with clinical features and survival was estimated using Kaplan-Meier methods with log-rank tests. RESULTS: In total, 155 cases passed quality control for STAG2 IHC. STAG2 expression in 20/155 cases could not be categorised with the limited available tissue, leaving 135 patients with definitive STAG2 IHC. In localised and metastatic disease, STAG2 was lost in 29/108 and 6/27 cases, respectively. Among patients with IHC and sequencing, 0/17 STAG2 expressing cases had STAG2 mutations, and 2/7 cases with STAG2 loss had STAG2 mutations. Among patients with localised disease, 5-year event-free survival was 54% (95% CI 34-70%) and 75% (95% CI 63-84%) for patients with STAG2 loss vs. expression (P = 0.0034). CONCLUSION: STAG2 loss of expression is identified in a population of patients without identifiable STAG2 mutations and carries a poor prognosis.

Rapid and highly sensitive approach for multiplexed somatic fusion detection.

Somatic gene translocations are key to making an accurate diagnosis in many cancers including many pediatric sarcomas. Currently available molecular diagnostic approaches to identifying somatic pathognomonic translocations have limitations such as minimal multiplexing, high cost, complex computational requirements, or slow turnaround times. We sought to develop a new fusion-detection assay optimized to mitigate these challenges. To accomplish this goal, we developed a highly sensitive multiplexed digital PCR-based approach that can identify the gene partners of multiple somatic fusion transcripts. This assay was validated for specificity with cell lines and synthetized DNA fragments. Assay sensitivity was optimized using a tiered amplification approach for fusion detection from low input and/or degraded RNA. The assay was then tested for the potential application of fusion detection from FFPE tissue and liquid biopsy samples. We found that this multiplexed PCR approach was able to accurately identify the presence of seven different targeted fusion transcripts with a turnaround time of 1 to 2 days. The addition of a tiered amplification step allowed the detection of targeted fusions from as little as 1 pg of RNA input. We also identified fusions from as little as two unstained slides of FFPE tumor biopsy tissue, from circulating tumor cells collected from tumor-bearing mice, and from liquid biopsy samples from patients with known fusion-positive cancers. We also demonstrated that the assay could be easily adapted for additional fusion targets. In summary, this novel assay detects multiple somatic fusion partners in biologic samples with low tumor content and low-quality RNA in less than two days. The assay is inexpensive and could be applied to surgical and liquid biopsies, particularly in places with inadequate resources for more expensive and expertise-dependent assays such as next-generation sequencing.

Role of bone marrow biopsy for staging new patients with Ewing sarcoma: A systematic review.

The incidence of bone marrow metastasis (BMM) in newly diagnosed Ewing sarcoma (ES) is variable across studies. An optimal staging strategy for detecting BMM is not defined. While bone marrow (BM) biopsy and/or aspirate (BMBA) have been the gold standard, [F-18]fluorodeoxyglucose positron emission tomography (FDG-PET) to detect BMM may decrease reliance on BMBA. We conducted a systematic review to assess incidence of BMM and the role of FDG-PET. We observed a pooled incidence of BMM by BMBA of 4.8% in all newly diagnosed ES patients and 17.5% among patients with metastatic disease. Only 1.2% of patients had BMM as their sole metastatic site. FDG-PET detection of BMM compared to BMBA demonstrated pooled 100% sensitivity and 96% specificity, positive predictive value of 75%, and negative predictive value of 100%. In the era of FDG-PET imaging, omission of BMBA may be considered in patients with otherwise localized disease after initial staging studies.

Derivation and validation of risk groups in patients with osteosarcoma utilizing regression tree analysis.

BACKGROUND: For patients with osteosarcoma, apart from stage and primary site, we lack reliable prognostic factors for risk stratification at diagnosis. There is a need for further defined, discrete prognostic groups using presenting clinical features. METHODS: We analyzed a cohort of 3069 patients less than 50 years of age, diagnosed with primary osteosarcoma of the bone between 1986 and 2013 from the Surveillance, Epidemiology, and End Results (SEER) database. Patients were randomly split into test and validation cohorts. Optimal cut points for age, tumor size, and grade were identified using classification and regression tree analysis. Manual recursive partitioning was used to identify discrete prognostic groups within the test cohort. These groups were applied to the validation cohort, and overall survival was analyzed using Cox models, Kaplan Meier methods, and log-rank tests. RESULTS: After applying recursive partitioning to the test cohort, our initial model included six groups. Application of these groups to the validation cohort resulted in four final groups. Key risk factors included presence of metastases, tumor site, tumor grade, age, and tumor size. Patients with localized axial tumors were identified as having similar outcomes to patients with metastases. Age and tumor size were only prognostically important in patients with extremity tumors when assessed in the validation cohort. CONCLUSIONS: This analysis supports prior reports that patients with axial tumors are a high-risk group, and demonstrates the importance of age and tumor size in patients with appendicular tumors. Biologic and genetic markers are needed to further define subgroups in osteosarcoma.

DICER1-associated central nervous system sarcoma in children: comprehensive clinicopathologic and genetic analysis of a newly described rare tumor.

The spectrum of neoplasms associated with DICER1 variants continues to expand, with the recent addition of primary "DICER1-associated central nervous system sarcoma" (DCS). DCS is a high-grade malignancy predominantly affecting pediatric patients. Six pediatric DCS were identified through a combination of clinical diagnostic studies, archival inquiry, and interinstitutional collaboration. Clinical, histologic, immunohistologic, and molecular features were examined. Genomic findings in the 6 DCS were compared with those in 14 additional DICER1-associated tumors sequenced with the same assay. The six patients presented at ages 3-15 years with CNS tumors located in the temporal (n = 2), parietal (n = 1), fronto-parietal (n = 1), and frontal (n = 2) lobes. All underwent surgical resection. Histologic examination demonstrated high-grade malignant spindle cell tumors with pleuropulmonary blastoma-like embryonic "organoid" features and focal rhabdomyoblastic differentiation; immature cartilage was seen in one case. Immunohistochemically, there was patchy desmin and myogenin staining, and patchy loss of H3K27me3, and within eosinophilic cytoplasmic globules, alfa-fetoprotein staining. Biallelic DICER1 variants were identified in all cases, with germline variants in two of five patients tested. DCS demonstrated genomic alterations enriched for Ras pathway activation and TP53 inactivation. Tumor mutational burden was significantly higher in the 6 DCS tumors than in 14 other DICER1-associated tumors examined (mean 12.9 vs. 6.8 mutations/Mb, p = 0.035). Postoperative care included radiation (n = 5) and chemotherapy (n = 3); at the last follow-up, three patients were alive without DCS, and three had died of disease. Our analysis expands the clinical, histologic, immunohistological, and molecular spectrum of DCS, identifying distinctive features that can aid in the diagnosis, multidisciplinary evaluation, and treatment of DCS.

Landscape of phase 1 clinical trials for minors with cancer in the United States.

OBJECTIVES: Understanding trends in characteristics of early phase trials that allow minors with cancer to participate may inform additional efforts to improve cancer drug development for young people. METHODS: We accessed data for oncology phase 1 or phase 1/2 trials in the United States from ClinicalTrials.gov with lower age bound for eligibility <18 years. Descriptive statistics were calculated and trends over time evaluated using logistic and multinomial logistic regression. RESULTS: Six hundred twelve trials met inclusion criteria. Sixty-five percent of trials were for older adults that also allowed minors, while 9% were exclusively for patients ≤18 years of age. Eighty-three percent of trials included at least one novel agent, while 17% studied only conventional therapies. Fifty-eight percent of trials studied treatments not yet Food and Drug Administration (FDA) approved (48% if exclusively for patients ≤18 years). Fifteen percent of trials for which dose-escalation method could be determined, utilized a model-based design. Eighteen percent of all trials were industry sponsored (48% if exclusively for patients ≤18 years). Forty-nine percent of all trials were multicenter (69% if exclusively for patients ≤18 years). There was an increase in trials exclusively focused on patients with central nervous system (CNS) tumors over the study period (P ≤ .02). No other temporal trends were seen. The median times from first-in-adult to first-in-pediatric for monotherapy and combination trials were 5.7 and 3.3 years, respectively. CONCLUSION: The paucity of clear temporal trends highlights the need for innovation in early drug development for young people. Our analysis serves as a benchmark against which to evaluate initiatives to improve pediatric cancer drug development.

The use of interval-compressed chemotherapy with the addition of vincristine, irinotecan, and temozolomide for pediatric patients with newly diagnosed desmoplastic small round cell tumor.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is a rare aggressive sarcoma that affects children and young adults, and portends poor outcomes despite intensive multimodal treatment approaches. We report toxicity, response, and outcomes of patients with DSRCT treated with the addition of vincristine, irinotecan, and temozolomide (VIT) to interval-compressed chemotherapy as per Children's Oncology Group ARST08P1. METHODS: All newly diagnosed pediatric patients with DSRCT treated at Dana-Farber Cancer Institute and Boston Children's Hospital between 2014 and 2019 as per ARST08P1, Arm P2 with replacement of VAC cycles with VIT, were identified. Medical records were reviewed for clinical and disease characteristics, and treatment response and outcomes. RESULTS: Six patients were treated as per the above regimen. Median age at diagnosis was 15.1 years (range 3.2-16.4) and five patients were male. Five patients had abdominal primary tumors, of which one had exclusively intraabdominal and four had extraabdominal metastases. Two initial cycles of VIT were well tolerated with nausea, vomiting, diarrhea, and constipation as the most common adverse events. Overall response rate defined as partial or complete response after two initial cycles of VIT was 50%. For local control, all patients had surgical resection followed by radiotherapy, and two patients received hyperthermic intraperitoneal chemotherapy at the time of surgery. Of the four patients who have completed therapy to date, three remain disease-free with median follow-up time of 46.7 months. CONCLUSIONS: The addition of VIT to interval-compressed chemotherapy is tolerable and active in DSRCT, with activity warranting additional investigation.

Using Liquid Biopsy in the Treatment of Patient with OS.

Liquid biopsies encompass a number of new technologies designed to derive tumor data through the minimally invasive sampling of an accessible body fluid. These technologies remain early in their clinical development, and applications for patients with osteosarcoma are actively under investigation. In this chapter, we outline the current state of liquid biopsy technologies as they apply to cancer generally and osteosarcoma specifically, focusing on assays that detect and profile circulating tumor DNA (ctDNA), microRNAs (miRNA), and circulating tumor cells (CTCs). At present, ctDNA assays are the most mature, with multiple assays demonstrating the feasibility of detecting and quantifying ctDNA from blood samples of patients with osteosarcoma. Initial studies show that ctDNA can be detected in the majority of patients with osteosarcoma and that the detection and level of ctDNA correlates with a worse prognosis. Profiling of ctDNA can also identify specific somatic events that may have prognostic relevance, such as 8q gain in osteosarcoma. miRNAs are stable RNAs that regulate gene expression and are known to be dysregulated in cancer, and patterns of miRNA expression have been evaluated in multiple studies of patients with osteosarcoma. While studies have identified differential expression of many miRNAs in osteosarcomas compared to healthy controls, a consensus set of prognostic miRNAs has yet to be definitively validated. Recent studies have also demonstrated the feasibility of capturing CTCs in patients with osteosarcoma. The development of assays that quantify and profile CTCs for use as prognostic biomarkers or tools for biologic discovery is still in development. However, CTC technology holds incredible promise given the potential to perform multi-omic approaches in single cancer cells to understand osteosarcoma heterogeneity and tumor evolution. The next step required to move liquid biopsy technologies closer to helping patients will be wide-scale collection of patient samples from large prospective studies.

Correction: Detection of circulating tumour DNA is associated with inferior outcomes in Ewing sarcoma and osteosarcoma: a report from the Children's Oncology Group.

The authors have noticed that the final paragraph of the Results section contains errors in the number of patients involved. The correct number of patients is included in the text below. These errors do not affect the Figure referenced.In osteosarcoma, we focused on 8q gain as a specific biological feature of interest. Among the 41 patients with detectable ctDNA in the osteosarcoma cohort, 8q gain was detected in 73.2% (30/41). The 3-year EFS for patients with 8q gain (n = 30) in ctDNA was 60.0% (95% CI 40.5-75.0) compared to 80.8 (95% CI 42.4-94.9) in patients without 8q gain (n = 11) in ctDNA (p = 0.18; Fig. 3).

Second malignancies in patients treated for Ewing sarcoma: A systematic review.

The therapies used to treat Ewing sarcoma are associated with a risk of second malignant neoplasm (SMN). We conducted a systematic review to pool available evidence on the risks, types, and outcomes after SMN. We obtained 52 articles that met inclusion criteria. Cumulative incidence rates of SMN ranged from 0.9 to 8.4% and 10.1 to 20.5% at 5 and 30 years after initial diagnosis. Of the 327 reported SMNs, 63.6% were solid tumors, although acute myeloid leukemia /myelodysplastic syndrome was the single most commonly diagnosed SMN, with generally poor outcomes. Patients treated for Ewing sarcoma are at substantial risk of SMN, with a broad range of reported secondary cancers.

Assessment of circulating tumor DNA in pediatric solid tumors: The promise of liquid biopsies.

Circulating tumor DNA can be detected in the blood and body fluids of patients using ultrasensitive technologies, which have the potential to improve cancer diagnosis, risk stratification, noninvasive tumor profiling, and tracking of treatment response and disease recurrence. As we begin to apply "liquid biopsy" strategies in children with cancer, it is important to tailor our efforts to the unique genomic features of these tumors and address the technical and logistical challenges of integrating biomarker testing. This article reviews the literature demonstrating the feasibility of applying liquid biopsy to pediatric solid malignancies and suggests new directions for future studies.

A single institutional review of pediatric Bacillus spp. bloodstream infections demonstrates increased incidence among children with cancer.

BACKGROUND: Bacillus species are known to cause severe infection in immunocompromised hosts. The incidence of Bacillus bloodstream infections and characteristics of infection among children with cancer or indication for hematopoietic cell transplant (HCT) is unknown. METHODS: We performed a retrospective medical record review of all cases of Bacillus bacteremia between January 1, 2005, and December 31, 2014, at Boston Children's Hospital. We report average incidences from 2012 to 2014. We performed a detailed review of infections among children with cancer or undergoing HCT and a case-control study to evaluate whether neutropenia at diagnosis caries higher risk of Bacillus infection for children with acute lymphoblastic leukemia (ALL). RESULTS: One hundred fourteen children developed Bacillus bacteremia during the study period, with an estimated incidence of 0.27/1,000 patients. Among children treated for cancer or undergoing HCT, there were 37 bloodstream infections (2.0/1,000 patients). Of the 37 oncology/HCT patients, oncologic diagnoses included ALL (18), acute myeloid leukemia (3), myelodysplastic syndrome (1), solid tumors (8), and 7 children were undergoing HCT. The incidence of infection among children with ALL was 34/1,000 patients and all central nervous system (CNS) infections (6) and deaths (3) occurred in this population. Neutropenia at time of diagnosis in children with ALL was not associated with risk of infection (P = 0.17). DISCUSSION: We report the first hospital-wide analysis of Bacillus infection and found that immunocompromised children experience a significant proportion of Bacillus infections. Children with ALL have a high incidence of infection and are at higher risk of CNS involvement and death.

Pediatric post-transplant hepatic kaposi sarcoma due to donor-derived human herpesvirus 8.

In areas of the world where human herpesvirus 8 (HHV-8) is endemic, Kaposi sarcoma (KS) is a common SOT-associated cancer. In the United States, where the virus is not prevalent, PTKS is rare, and there is little literature on pediatric PTKS. We present a North American female who underwent deceased donor, left lateral segment liver transplant for biliary atresia at age 11 months. The donor was a male with no known history of KS, originally from an HHV-8-endemic country. Three months after transplantation, the patient developed liver nodules and portal vein thrombosis. Analysis of needle biopsy established the diagnosis of KS and confirmed that the transformed cells were donor-derived. HHV-8 viremia was detected, and ganciclovir dosing (which had been started prophylactically) was increased. Immunosuppression was changed from tacrolimus to sirolimus. After further disease progression, 8 cycles of paclitaxel were administered. Under this treatment, her nodules regressed, HHV-8 viremia resolved, and she had marked clinic improvement. Notably, the adult recipient of the right liver lobe from the same donor also developed PTKS. This is one of few pediatric PTKS cases described in the literature. It contributes to the mechanistic understanding of PTKS development, illustrating the risk posed by donors from HHV-8-endemic countries, as well as the potential for strong PTKS correlation between multiple recipients of organs from a single shared donor.

Detection of circulating tumour DNA is associated with inferior outcomes in Ewing sarcoma and osteosarcoma: a report from the Children's Oncology Group.

BACKGROUND: New prognostic markers are needed to identify patients with Ewing sarcoma (EWS) and osteosarcoma unlikely to benefit from standard therapy. We describe the incidence and association with outcome of circulating tumour DNA (ctDNA) using next-generation sequencing (NGS) assays. METHODS: A NGS hybrid capture assay and an ultra-low-pass whole-genome sequencing assay were used to detect ctDNA in banked plasma from patients with EWS and osteosarcoma, respectively. Patients were coded as positive or negative for ctDNA and tested for association with clinical features and outcome. RESULTS: The analytic cohort included 94 patients with EWS (82% from initial diagnosis) and 72 patients with primary localised osteosarcoma (100% from initial diagnosis). ctDNA was detectable in 53% and 57% of newly diagnosed patients with EWS and osteosarcoma, respectively. Among patients with newly diagnosed localised EWS, detectable ctDNA was associated with inferior 3-year event-free survival (48.6% vs. 82.1%; p = 0.006) and overall survival (79.8% vs. 92.6%; p = 0.01). In both EWS and osteosarcoma, risk of event and death increased with ctDNA levels. CONCLUSIONS: NGS assays agnostic of primary tumour sequencing results detect ctDNA in half of the plasma samples from patients with newly diagnosed EWS and osteosarcoma. Detectable ctDNA is associated with inferior outcomes.

Outcomes Following Bone Marrow Transplantation in Children With Accelerated Phase or Blast Crisis Chronic Myelogenous Leukemia in the Era of Tyrosine Kinase Inhibitors.

The management of chronic myelogenous leukemia (CML) in children changed dramatically with the introduction of tyrosine kinase inhibitors (TKIs). Unfortunately, outcomes for patients presenting in an advanced stage-accelerated phase or blast crisis CML-continues to be poor, requiring chemotherapy and allogeneic hematopoietic stem cell transplant (HSCT) to attempt cure. Integration of TKIs in the therapy of advanced CML is still an area of active investigation. There are little published data on TKI use in children with advanced stage CML. We performed a retrospective review of all children treated at our institution between January 1, 2010 and June 30, 2013, and identified 5 children, age 12 to 18 years, with advanced stage CML. All patients were treated with a TKI before HSCT and TKIs were restarted post-HSCT in 4/5 with a goal of continuing until 2 years posttransplant. At time of HSCT all were in a morphologic and cytogenetic remission; 1 patient had also achieved molecular remission. All patients are alive and in molecular remission at an average of 38 months (range, 14 to 51 mo) following transplant. Our experience indicates that TKIs are safe and well tolerated in children both pretransplant and posttransplant and may improve outcomes in this aggressive disease.

Off-label prescribing of immune checkpoint inhibitor therapy at a single pediatric cancer center.

BACKGROUND: Immune checkpoint inhibitors (ICI) have improved outcomes in a variety of adult cancers and are prescribed with increasing frequency across oncology. However, patterns of off-label use of ICI in pediatrics remain unclear. METHODS: This is a single-institution, retrospective cohort study evaluating off-label ICI use in pediatric and young adult patients with cancer treated at our institution from 2014 to 2022. Response was based on clinician assessment derived from clinical records. Immune-related adverse events (iRAEs) were classified according to CTCAE v5.0. RESULTS: We identified 50 unique patients treated with off-label ICI (28 with solid tumors, 20 with central nervous system (CNS) tumors, 2 with hematologic malignancies). At time of ICI initiation, only five patients (10%) had localized disease, and all but one patient was treated in the relapsed/refractory setting. All patients were treated with the FDA-approved weight-based dosing recommendations. Overall, there was disease control in 21 patients (42%), with best response including one complete response (melanoma), two partial responses (high-grade glioma, CNS nongerminomatous germ cell tumor), and 18 patients with stable disease. Forty-four patients (88%) eventually experienced disease progression. Among 22 patients (44%) experiencing iRAEs, 10 (20%) had a grade ≥3 irAE, 12 (24%) required corticosteroids, and 14 (28%) required ICI discontinuation. irAE occurrence was associated with significantly improved progression-free survival (HR 0.35; 95% CI: 0.18 to 0.68; p = 0.002) and overall survival (HR 0.33; 95% CI: 0.17 to 0.66; p = 0.002). CONCLUSIONS: At our institution, ICI was most commonly prescribed in the relapsed/refractory setting to patients with metastatic disease. The treatment was generally well-tolerated in the pediatric population. The overall response rate was low, and the majority of patients eventually experienced disease progression. A few patients, however, had durable treatment responses. Further studies are needed to identify which pediatric patients are most likely to benefit from ICI.

Poverty, race, ethnicity, and survival in pediatric nonmetastatic osteosarcoma: a Children's Oncology Group report.

BACKGROUND: Children living in poverty and those of marginalized race or ethnicity experience inferior disease outcomes across many cancers. Whether survival disparities exist in osteosarcoma is poorly defined. We investigated the association between race, ethnicity, and proxied poverty exposures and event-free and overall survival for children with nonmetastatic osteosarcoma receiving care on a cooperative group trial. METHODS: We conducted a retrospective cohort study of US patients with nonmetastatic, osteosarcoma aged 5-21 years enrolled on the Children's Oncology Group trial AOST0331. Race and ethnicity were categorized to reflect historically marginalized populations, as Hispanic, non-Hispanic Black, non-Hispanic Other, and non-Hispanic White. Poverty was proxied at the household and neighborhood levels. Overall survival and event-free survival functions of time from trial enrollment were estimated using the Kaplan-Meier method. Hypotheses of associations between risks for event-free survival, death, and postrelapse death with race and ethnicity were assessed using log-rank tests. RESULTS: Among 758 patients, 25.6% were household-poverty and 28.5% neighborhood-poverty exposed. Of the patients, 21% of children identified as Hispanic, 15.4% non-Hispanic Black, 5.3% non-Hispanic Other, and 54.0% non-Hispanic White. Neither household or neighborhood poverty nor race and ethnicity were statistically significantly associated with risks for event-free survival or death. Postrelapse risk for death differed statistically significantly across race and ethnicity with non-Hispanic Black patients at greatest risk (4-year postrelapse survival 35.7% Hispanic vs 13.0% non-Hispanic Black vs 43.8% non-Hispanic Other vs 38.9% non-Hispanic White; P = .0046). CONCLUSIONS: Neither proxied poverty exposures or race and ethnicity were associated with event-free survival or overall survival, suggesting equitable outcomes following frontline osteosarcoma trial-delivered therapy. Non-Hispanic Black children experienced statistically significant inferior postrelapse survival. Investigation of mechanisms underlying postrelapse disparities are paramount.