Ewing sarcoma (ES) is a malignant tumor of bone and soft tissue that most often occurs in children, adolescents, and young adults. Debate and controversy remain in the management of relapsed/refractory ES (RR-ES). The authors leveraged the expertise assembled by the National Ewing Sarcoma Tumor Board, a multidisciplinary virtual tumor board that meets monthly to discuss challenging cases of ES. In this review, they focus on select topics that apply to the management of patients with RR-ES. The specific topics covered include the initial approach of such patients and discussion of the goals of care, the role of molecular testing, chemotherapy regimens and novel agents to consider, the role of maintenance therapy, and the use of high-dose chemotherapy with autologous stem cell rescue. The data referenced are often limited to subgroup analyses and/or compiled from multiple sources. Although not intended to replace the clinical judgement of treating physicians, these guidelines are intended to support clinicians and provide some clarity and recommendations for the management of patients with RR-ES. PLAIN LANGUAGE SUMMARY: Ewing sarcoma (ES) is a bone and soft tissue cancer that most often occurs in teenagers and young adults. This article uses the experience of the National Ewing Sarcoma Tumor Board, a multi-institution, multidisciplinary virtual tumor board that meets monthly to discuss challenging cases of ES and to address questions related to the treatment of patients with relapsed ES. Although not intended to replace the clinical judgement of treating physicians and limited by available data, these consensus recommendations will support clinicians who treat patients with this challenging malignancy, made even more difficult when it recurs.

Ewing sarcoma is a small round-cell sarcoma characterized by gene fusion involving EWSR1 (or another TET family protein like FUS) and an ETS family transcription factor. The estimated incidence of this rare bone tumor, which occurs most frequently in adolescents and young adults, is 0.3 per 100,000/year. Although only 25% of patients with Ewing sarcoma are diagnosed with metastatic disease, historical series show that this is a systemic disease. Patient management requires multimodal therapies-including intensive chemotherapy-in addition to local treatments (surgery and/or radiotherapy). In the recurrent/refractory disease setting, different approaches involving systemic treatments and local therapies are also recommended as well as patient inclusion in clinical trials whenever possible. Because of the complexity of Ewing sarcoma diagnosis and treatment, it should be carried out in specialized centers and treatment plans should be designed upfront by a multidisciplinary tumor board. These guidelines provide recommendations for diagnosis, staging, and multimodal treatment of Ewing sarcoma.

BACKGROUND: Multidrug chemotherapy for Ewing sarcoma can lead to severe myelosuppression. We proposed two clinical questions (CQ): CQ #1, \"Does primary prophylaxis with G-CSF benefit chemotherapy for Ewing sarcoma?\" and CQ #2, \"Does G-CSF-based intensified chemotherapy improve Ewing sarcoma treatment outcomes?\".
METHODS: A comprehensive literature search was conducted in PubMed, Cochrane Library, and Ichushi web databases, including English and Japanese articles published from 1990 to 2019. Two reviewers assessed the extracted papers and analyzed overall survival (OS), febrile neutropenia (FN) incidence, infection-related mortality, quality of life (QOL), and pain.
RESULTS: Twenty-five English and five Japanese articles were identified for CQ #1. After screening, a cohort study of vincristine, ifosfamide, doxorubicin, and etoposide chemotherapy with 851 patients was selected. Incidence of FN was 60.8% with G-CSF and 65.8% without; statistical tests were not conducted. Data on OS, infection-related mortality, QOL, or pain was unavailable. Consequently, CQ #1 was redefined as a future research question. As for CQ #2, we found two English and five Japanese papers, of which one high-quality randomized controlled trial on G-CSF use in intensified chemotherapy was included. This trial showed trends toward lower mortality and a significant increase in event-free survival for 2-week interval regimen with the G-CSF primary prophylactic use compared with 3-week interval.
CONCLUSIONS: This review indicated that G-CSF\'s efficacy as primary prophylaxis in Ewing sarcoma, except in children, is uncertain despite its common use. This review tentatively endorses intensified chemotherapy with G-CSF primary prophylaxis for Ewing sarcoma.

BACKGROUND: Patients with high-risk or metastatic Ewing sarcoma (ES) and rhabdomyosarcoma (RMS) have a guarded prognosis. High-dose chemotherapy (HDT) with autologous stem cell transplant (ASCT) has been evaluated as a treatment option to improve outcomes. However, survival benefits remain unclear, and treatment is associated with severe toxicities.
METHODS: A systematic review was conducted, using the population, intervention, comparison outcome (PICO) model, to evaluate whether utilization of HDT/ASCT impacts the outcome of patients with ES and RMS compared to standard chemotherapy alone, as part of first line treatment or in the relapse setting. Medline, Embase and Cochrane Central were queried for publications from 1990 to October 2022 that evaluated event-free survival (EFS), overall survival (OS), and toxicities. Each study was screened by two independent reviewers for suitability. A qualitative synthesis of the results was performed.
RESULTS: Of 1,172 unique studies screened, 41 studies were eligible for inclusion with 29 studies considering ES, 10 studies considering RMS and 2 studies considering both. In ES patients with high-risk localised disease who received HDT/ASCT after VIDE chemotherapy, consolidation with melphalan-based HDT/ASCT as first line therapy conveyed an EFS and OS benefit over standard chemotherapy consolidation. Efficacy of HDT/ASCT using a VDC/IE backbone, which is now standard care, has not been established. Survival benefits are not confirmed for ES patients with metastatic disease at initial diagnosis. For relapsed/refractory ES, four retrospective studies report improvement in outcomes with HDT/ASCT with the greatest evidence in patients who demonstrate a treatment response before HDT, and in patients under the age of 14. In RMS, there is no proven survival benefit of HDT/ASCT in primary localised, metastatic or relapsed disease.
CONCLUSIONS: Prospective randomised trials are required to determine the utility of HDT/ASCT in ES and RMS. Selected patients with relapsed ES could be considered for HDT/ASCT.

Ewing sarcoma (ES) is a malignant tumor of bone and soft tissue that most often occurs in adolescents and young adults. Despite an international coordinated approach, several nuances, discrepancies, and debates remain in defining the standard of care for treating ES. In this review, the authors leverage the expertise assembled by formation of the National Ewing Sarcoma Tumor Board, a multi-institution, multidisciplinary virtual tumor board that meets monthly to discuss complicated and challenging cases of ES. This report is focused on select topics that apply to the management of patients with newly diagnosed ES. The specific topics covered include indications for bone marrow aspirate and biopsy for initial evaluation compared with fluorodeoxyglucose-positron emission tomography, the role of interval compressed chemotherapy in patients aged 18 years and older, the role of adding ifosfamide/etoposide to vincristine/doxorubicin/cyclophosphamide for patients with metastatic disease, the data on and role of high-dose chemotherapy with autologous stem cell transplantation, maintenance therapy, and whole-lung irradiation. The data referenced are often limited to subgroup analyses and/or compiled from multiple sources. Although not intended to replace the clinical judgement of treating physicians, the guidelines are intended to provide clarity and recommendations for the upfront management of patients with ES. PLAIN LANGUAGE SUMMARY: Ewing sarcoma is a malignant tumor of bone and soft tissue that most often occurs in adolescents and young adults. For this review, the authors used the experience of the National Ewing Sarcoma Tumor Board, a multi-institution, multidisciplinary virtual tumor board that meets monthly to discuss complicated and challenging cases of Ewing sarcoma. Although not intended to replace the clinical judgement of treating physicians, the guidelines will focus on the development of consensus statements for the upfront management of patients with Ewing sarcoma.

BACKGROUND: The local treatment of Ewing sarcoma of bone involves surgery, radiotherapy or both. The selection of treatment depends on the anatomical extent of the tumour, the effectiveness of the proposed treatment, its morbidity, and the expectation of cure. However, not only are there variations in the approach to local treatment between individual patients, but also between treatment centres and countries. Our aim was to explore variation in practice and develop consensus statements about local treatment.
METHODS: A three stage modified Delphi technique was used with international collaborators. This involved an expert panel to identify areas of controversy, an online survey of international collaborators and a consensus meeting in London, UK in June 2017. In the consensus meeting, teams of clinicians discussed the local management of selected cases and their responses were collected with electronic voting.
RESULTS: Areas of greater or less consensus were identified. The lack of evidence underpinning different approaches was noted and areas for collaborative research became apparent.
CONCLUSIONS: This has demonstrated that there is an international consensus around many aspects of the local treatment of Ewing sarcoma of bone, including the use of specialist MultiDisciplinary Team (MDT) meetings with access to all appropriate treatments. However, considerable variation remains including the use of different staging investigations, decision making, definitions of response, and radiotherapy doses and timing. Further collaborative work should be undertaken to determine the impact of these variations in order to define best practice.

Standardized reports are essential to meeting the bone sarcoma reference center certification requirements of the French National Cancer Institute (INCa). The usual classifications of the Musculoskeletal Tumor Society (MSTS), the American Joint Committee on Cancer (AJCC/IUCC) TNM R classification and the American College of Pathologists, are inexact inasmuch as they fail to include chemotherapy impact on tumor cells in assessing surgical margins. This leads to inconsistent interpretation by teams managing bone sarcoma. The present literature analysis sought to assess the limitations of existing classifications for purposes of standardized reporting of the management of surgical specimens from patients with osteosarcoma or Ewing sarcoma receiving neoadjuvant chemotherapy, by addressing the following questions: 1) What is the prognostic value of margins and chemotherapy response in the classifications? 2) What are the histologic changes induced by chemotherapy, with what impact on interpretation of margins?
A PubMed literature analysis was performed, targeting the prognostic value of resection margin assessment, in September 2018. French bone pathology group (Groupe français des pathologistes osseux) and international guidelines on bone specimen management were referred to so as select items for a standardized report. Eight of the 523 articles retrieved met the study eligibility criteria.
Minimal distance between tumor and surgical margin, with a>2mm threshold, seemed to be the optimal parameter for predicting local recurrence. Good chemotherapy response and appendicular skeletal location were associated with lower risk of local recurrence. None of the available classifications take into account the microscopic changes induced by chemotherapy in interpreting resection margins.
To standardize practice, GROUPOS developed a standardized report for bone sarcoma specimens, considering the histopathologic changes in the tumor after neoadjuvant chemotherapy. The TNM R system was adapted and a threshold of>2mm was chosen as an acceptable limit to qualify surgical resection as safe (R0). R1 status (≤2mm) was subdivided into subgroups a, b and c, to include margin measurement in relation to the post-chemotherapy scar: R1a, resection within the scar; R1b, resection in healthy tissue,≤2mm from the scar and/or residual viable cells; and R1c, resection within the lesion in contact with viable cells or within coagulation necrosis areas. The GROUPOS members drew up this standardized report so as to ensure a common language, improving bone sarcoma management in specialized centers. Reliable data can thus be established for national and international multicenter studies.
IV.

Teenagers and young adults (TYA) cancer contributes substantially to morbidity and mortality in a population with much to offer society. TYA place distinct challenges upon cancer care services, many reporting feeling marginalized and their needs not being met in adult or paediatric cancer services. Bone tumours such as osteosarcoma and Ewing sarcoma, because of their age at presentation and the complexity of their care, are where challenges in managing (TYA) with cancer have often been most readily apparent. Bone sarcomas may be managed by paediatric or medical oncologists, and require fastidious attention to protocol. A lack of recent improvement in survival in TYA with bone tumours may be linked to a lack of specialist care, poor concordance with therapy in some situations and TYA-specific pharmacology. Participation in clinical trials, particularly of young adults, is low, hindering progress. All these requirements may be best met by a concerted effort to create collaborative care between adult and paediatric experts in bone sarcoma, working together to meet TYA patients\' needs.