Advancing preclinical biology for Ewing Sarcoma: an international effort.

Ewing sarcoma (EwS) is an aggressive bone and soft tissue cancer affecting adolescents and young adults. In vitro and in vivo models of EwS have been instrumental in advancing our understanding of EwS biology and essential in evaluating potential therapies, particularly for metastatic or relapsed disease where effective treatment options remain limited. Through an international collaborative effort between the Children's Oncology Group (COG) Bone Tumor Committee and the Euro Ewing Consortium (EEC), we review the current landscape of preclinical modeling used in EwS research encompassing both in vitro (cell lines and tumor organoids) and in vivo (mouse and non-mammalian xenografts) model systems.

Emerging Role of Blood-based Biomarkers in Sarcomas.

We assess the emerging role of liquid biopsies, particularly circulating tumor DNA (ctDNA), in sarcoma management. Preliminary studies suggest that ctDNA has multiple potential applications including, early detection in patients with cancer predisposition syndromes, diagnosis, prognostication, therapy selection, and monitoring treatment response. Among patients with gastrointestinal stromal tumors, studies have demonstrated the capacity for identification of clinically relevant resistance mutations.

Molecular characterization informs prognosis in patients with localized Ewing sarcoma: A report from the Children's Oncology Group.

Purpose: Identification of discrete sub-groups associated with treatment response and resistance in localized Ewing sarcoma (EWS) remains a challenge. The primary objective of the Children's Oncology Group biology study AEWS18B1-Q was to perform molecular characterization of a large cohort of patients with localized Ewing sarcoma treated on prospective trials with modern standard of care therapy.

Methods: We analyzed clinical and molecular features from patients with localized EWS enrolled on AEWS0031, AEWS1031, or INT-0154 frontline trials.

Rare germline structural variants increase risk for pediatric solid tumors.

Pediatric solid tumors are a leading cause of childhood disease mortality. In this work, we examined germline structural variants (SVs) as risk factors for pediatric extracranial solid tumors using germline genome sequencing of 1765 affected children, their 943 unaffected parents, and 6665 adult controls. We discovered a sex-biased association between very large (>1 megabase) germline chromosomal abnormalities and increased risk of solid tumors in male children.

Larotrectinib for Newly Diagnosed Infantile Fibrosarcoma and Other Pediatric Fusion-Positive Solid Tumors (Children's Oncology Group ADVL1823).

Purpose: The TRK inhibitor larotrectinib is US Food and Drug Administration approved for fusion-positive solid tumors that lack a satisfactory alternative or have progressed after treatment but has not been systematically studied as a frontline therapy with a defined duration of treatment. ADVL1823 evaluated larotrectinib in patients with newly diagnosed fusion-positive solid tumors with response-adapted duration of therapy and local control.

Methods: Patients received larotrectinib twice daily in 28-day cycles for a predefined duration of treatment, ranging from 6 to 26 cycles depending on response to therapy and surgical resectability.

Rare germline structural variants increase risk for pediatric solid tumors.

Pediatric solid tumors are rare malignancies that represent a leading cause of death by disease among children in developed countries. The early age-of-onset of these tumors suggests that germline genetic factors are involved, yet conventional germline testing for short coding variants in established predisposition genes only identifies pathogenic events in 10-15% of patients. Here, we examined the role of germline structural variants (SVs)-an underexplored form of germline variation-in pediatric extracranial solid tumors using germline genome sequencing of 1,766 affected children, their 943 unaffected relatives, and 6,665 adult controls.

Targeting TRIP13 in favorable histology Wilms tumor with nuclear export inhibitors synergizes with doxorubicin.

Wilms tumor (WT) is the most common renal malignancy of childhood. Despite improvements in the overall survival, relapse occurs in ~15% of patients with favorable histology WT (FHWT). Half of these patients will succumb to their disease.

Germline Genetic Testing and Survival Outcomes Among Children With Rhabdomyosarcoma: A Report From the Children's Oncology Group.

Importance: Determining the impact of germline cancer-predisposition variants (CPVs) on outcomes could inform novel approaches to testing and treating children with rhabdomyosarcoma.

Objective: To assess whether CPVs are associated with outcome among children with rhabdomyosarcoma.

Design, Setting, And Participants: In this cohort study, data were obtained for individuals, aged 0.

Osteosarcoma Explorer: A Data Commons With Clinical, Genomic, Protein, and Tissue Imaging Data for Osteosarcoma Research.

Purpose: Osteosarcoma research advancement requires enhanced data integration across different modalities and sources. Current osteosarcoma research, encompassing clinical, genomic, protein, and tissue imaging data, is hindered by the siloed landscape of data generation and storage.

Materials And Methods: Clinical, molecular profiling, and tissue imaging data for 573 patients with pediatric osteosarcoma were collected from four public and institutional sources.

Phase 2 trial of palbociclib and ganitumab in patients with relapsed Ewing sarcoma.

Background: Ewing sarcoma (EWS) is an aggressive sarcoma with few treatment options for patients with relapsed disease. Cyclin-dependent kinase 4 (CDK4) is a genomic vulnerability in EWS that is synergistic with IGF-1R inhibition in preclinical studies. We present the results of a phase 2 study combining palbociclib (CDK4/6 inhibitor) with ganitumab (IGF-1R monoclonal antibody) for patients with relapsed EWS.

Clinical Targeted Next-Generation Panel Sequencing Reveals Amplification Is a Poor Prognostic Factor in Osteosarcoma.

Purpose: Osteosarcoma risk stratification, on the basis of the presence of metastatic disease at diagnosis and histologic response to chemotherapy, has remained unchanged for four decades, does not include genomic features, and has not facilitated treatment advances. We report on the genomic features of advanced osteosarcoma and provide evidence that genomic alterations can be used for risk stratification.

Materials And Methods: In a primary analytic patient cohort, 113 tumor and 69 normal samples from 92 patients with high-grade osteosarcoma were sequenced with OncoPanel, a targeted next-generation sequencing assay.

Pilot Study of Recurrent Ewing's Sarcoma Management with Vigil/Temozolomide/Irinotecan and Assessment of Circulating Tumor (ct) DNA.

Purpose: Treatment options for recurrent or refractory Ewing's sarcoma (ES) are limited. Vigil is a novel autologous tumor cell therapy expressing bi-shRNA furin/GMCSF plasmid, which previously demonstrated monotherapy activity in advanced ES. Herein we report safety and evidence of benefit to Vigil for ES as potential treatment.

Circulating Tumor DNA Is Prognostic in Intermediate-Risk Rhabdomyosarcoma: A Report From the Children's Oncology Group.

Purpose: Novel biomarkers are needed to differentiate outcomes in intermediate-risk rhabdomyosarcoma (IR RMS). We sought to evaluate strategies for identifying circulating tumor DNA (ctDNA) in IR RMS and to determine whether ctDNA detection before therapy is associated with outcome.

Patients And Methods: Pretreatment serum and tumor samples were available from 124 patients with newly diagnosed IR RMS from the Children's Oncology Group biorepository, including 75 patients with fusion-negative rhabdomyosarcoma (FN-RMS) and 49 with fusion-positive rhabdomyosarcoma (FP-RMS) disease.

Randomized Phase III Trial of Ganitumab With Interval-Compressed Chemotherapy for Patients With Newly Diagnosed Metastatic Ewing Sarcoma: A Report From the Children's Oncology Group.

Purpose: Monoclonal antibodies directed against insulin-like growth factor-1 receptor (IGF-1R) have shown activity in patients with relapsed Ewing sarcoma. The primary objective of Children's Oncology Group trial AEWS1221 was to determine if the addition of the IGF-1R monoclonal antibody ganitumab to interval-compressed chemotherapy improves event-free survival (EFS) in patients with newly diagnosed metastatic Ewing sarcoma.

Methods: Patients were randomly assigned 1:1 at enrollment to standard arm (interval-compressed vincristine/doxorubicin/cyclophosphamide alternating once every 2 weeks with ifosfamide/etoposide = VDC/IE) or to experimental arm (VDC/IE with ganitumab at cycle starts and as monotherapy once every 3 weeks for 6 months after conventional therapy).

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.

An international working group consensus report for the prioritization of molecular biomarkers for Ewing sarcoma.

The advent of dose intensified interval compressed therapy has improved event-free survival for patients with localized Ewing sarcoma (EwS) to 78% at 5 years. However, nearly a quarter of patients with localized tumors and 60-80% of patients with metastatic tumors suffer relapse and die of disease. In addition, those who survive are often left with debilitating late effects.

Serrated Polyposis Syndrome in a Young Adolescent Patient.

Serrated polyps are pathological neoplastic lesions in the colon with subtle gross morphology leading to underreporting during colonoscopy. While detection rates are increasing in average-risk adult screening colonoscopy, the rate of detection during pediatric colonoscopy is unknown. Serrated polyposis syndrome is characterized by the presence of multiple serrated polyps in the colon and an increased risk of developing colorectal cancer.

Molecular profiling identifies targeted therapy opportunities in pediatric solid cancer.

To evaluate the clinical impact of molecular tumor profiling (MTP) with targeted sequencing panel tests, pediatric patients with extracranial solid tumors were enrolled in a prospective observational cohort study at 12 institutions. In the 345-patient analytical population, median age at diagnosis was 12 years (range 0-27.5); 298 patients (86%) had 1 or more alterations with potential for impact on care.

Circulating Tumor DNA as a Biomarker in Patients With Stage III and IV Wilms Tumor: Analysis From a Children's Oncology Group Trial, AREN0533.

Purpose: The utility of circulating tumor DNA (ctDNA) analyses has not been established in the risk stratification of Wilms tumor (WT). We evaluated the detection of ctDNA and selected risk markers in the serum and urine of patients with WT and compared findings with those of matched diagnostic tumor samples.

Patients And Methods: Fifty of 395 children with stage III or IV WT enrolled on Children's Oncology Group trial AREN0533 had banked pretreatment serum, urine, and tumor available.

Circulating Tumor DNA Is Associated with Response and Survival in Patients with Advanced Leiomyosarcoma.

Purpose: We sought to determine whether the detection of circulating tumor DNA (ctDNA) in samples of patients undergoing chemotherapy for advanced leiomyosarcoma (LMS) is associated with objective response or survival.

Experimental Design: Using ultra-low-passage whole-genome sequencing (ULP-WGS) of plasma cell-free DNA from patients treated on a prospective clinical trial, we tested whether detection of ctDNA evaluated prior to the start of therapy and after two cycles of chemotherapy was associated with treatment response and outcome. Associations between detection of ctDNA and pathologic measures of disease burden were evaluated.

Germline predisposition to pediatric Ewing sarcoma is characterized by inherited pathogenic variants in DNA damage repair genes.

More knowledge is needed regarding germline predisposition to Ewing sarcoma to inform biological investigation and clinical practice. Here, we evaluated the enrichment of pathogenic germline variants in Ewing sarcoma relative to other pediatric sarcoma subtypes, as well as patterns of inheritance of these variants. We carried out European-focused and pan-ancestry case-control analyses to screen for enrichment of pathogenic germline variants in 141 established cancer predisposition genes in 1,147 individuals with pediatric sarcoma diagnoses (226 Ewing sarcoma, 438 osteosarcoma, 180 rhabdomyosarcoma, and 303 other sarcoma) relative to identically processed cancer-free control individuals.

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.

Preclinical Modeling of Leiomyosarcoma Identifies Susceptibility to Transcriptional CDK Inhibitors through Antagonism of E2F-Driven Oncogenic Gene Expression.

Purpose: Leiomyosarcoma (LMS) is a neoplasm characterized by smooth muscle differentiation, complex copy-number alterations, tumor suppressor loss, and the absence of recurrent driver mutations. Clinical management for advanced disease relies on the use of empiric cytotoxic chemotherapy with limited activity, and novel targeted therapies supported by preclinical research on LMS biology are urgently needed. A lack of fidelity of established LMS cell lines to their mesenchymal neoplasm of origin has limited translational understanding of this disease, and few other preclinical models have been established.

Germline Sequencing Improves Tumor-Only Sequencing Interpretation in a Precision Genomic Study of Patients With Pediatric Solid Tumor.

Purpose: Molecular tumor profiling is becoming a routine part of clinical cancer care, typically involving tumor-only panel testing without matched germline. We hypothesized that integrated germline sequencing could improve clinical interpretation and enhance the identification of germline variants with significant hereditary risks.

Materials And Methods: Tumors from pediatric patients with high-risk, extracranial solid malignancies were sequenced with a targeted panel of cancer-associated genes.