Ewing Sarcoma

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유잉육종

주희영

삼성서울병원 소아청소년과

Ewing Sarcoma

Hee Young Ju

Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

Ewing sarcoma is the second most frequently occurring malignant tumor of the bone and soft tissue in adolescents and young adults. Genetically, Ewing sarcoma is charac- terized by balanced chromosomal translocation in which a member of FET gene family is fused with an ETS transcription factor, with the most common fusion being EWSR1-FLI1 (85% of cases). Treatment of Ewing sarcoma is based on multidisciplinary approach (local surgery, radiotherapy and multiagent chemotherapy), which are asso- ciated with chronic late effects that may compromise quality of life of survivors. First line treatment includes combination of drugs incorporating doxorubicin, vincristine, cy- clophosphamide, ifosfamide, etoposide, and dactinomycin. The beneficial role of high dose chemotherapy has been suggested in high-risk localized Ewing sarcoma patients, and the studies are being performed to investigate the role in metastatic disease. The 5-year overall survival for localized Ewing sarcoma has improved to reach 65% to 75%.

But patients with metastatic disease have a 5-year survival rate of ＜30%, except for those with isolated pulmonary metastasis (approximately 50%). Patients with recurrent tumor have a dismal prognosis. Novel therapeutic strategies based on understanding of molecular mechanisms are needed to improve the outcome of Ewing sarcoma and to lessen the treatment-related late effects.

pISSN 2233-5250 / eISSN 2233-4580 https://doi.org/10.15264/cpho.2019.26.1.27 Clin Pediatr Hematol Oncol 2019;26:27∼34

Received on March 25, 2019 Revised on April 4, 2019 Accepted on April 11, 2019

Corresponding Author: Hee Young Ju Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 06351, Korea

Tel: +82-2-3410-0870 Fax: +82-2-3410-0043 E-mail: [email protected] ORCID ID: orcid.org/0000-0001-6744-0412

Key Words: Ewing sarcoma, Peripheral primitive neuroectodermal tumors, EWS-FLI1 fu- sion protein

Introduction

1) Epidemiology

Ewing sarcoma is the second most common malignant bone or soft tissue sarcoma, mainly occurring in children, adolescents and young adults (AYA). The peak incidence age is 15 years old, which occurs more in male than female

with 3:2 ratio [1]. Ewing sarcoma predominantly affects the

bone of extremity (45%), thorax or abdomen (20%), or the

pelvis (19%). Approximately 20% of cases present the tu-

mor at extraskeletal sites (thigh, pelvis, paraspinal area, and

foot). Among newly diagnosed Ewing sarcoma patients,

20-25% present with metastasis at diagnosis. The incidence

rate of Ewing sarcoma is 1.5 cases per million children and

AYA globally. But the incidence of Ewing sarcoma was re-

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Fig. 1. FET-ETS fusion oncogenes reported to date in Ewing sarcoma. Ewing sarcoma is characterized by recurrent balanced translocation resulting in fusion of the FET gene family (FUS, EWSR1 or TAF15) with the ETS gene family (FLI1, ERG, ETV4 and FEV).

ported to be lower in Asian and African populations, with annual rates of 0.8 and 0.2 cases per million children, re- spectively [1,2]. By recent Korean report [3], age-stand- ardized ratio (ASR) of Ewing sarcoma was 1.4 per million, and highest ASR was observed in 10-14 years old group, which was similar with global report. Epidemiologic associ- ation studies have indicated higher rates of Ewing sarcoma in children of farm workers, but they are not considered as a risk factor [4]. Also, Ewing sarcoma is rarely observed among the cancer predisposition syndromes described to date [5]. Although the etiology of Ewing sarcoma is un- known, it is genetically well characterized.

2) Group of disease

Historically, the group ‘Ewing sarcoma family of tu- mours’ included the tumors based on morphological and immunophenotypical features and the presence of chromo- somal translocations. This group included extraosseous Ewing sarcoma, peripheral primitive neuroectodermal tu- mours and Askin tumours. However, the 2013 WHO classi- fication of sarcomas uniformly defined these tumours as

‘Ewing sarcoma’ [6,7], characterized by pathognomonic FET-ETS gene fusions [8,9]. The WHO classification also in- cludes the term ‘Ewing-like sarcomas’, which are small round cell sarcomas with morphologically similar appear- ances to Ewing sarcoma but are characterized by different fusion genes and clinical, pathological features. Ewing sar- coma is characterized by its driver mutations, specific chro- mosomal translocations that fuse a number of the FET fam- ily of protein (encoded by FUS, EWSR1 and TAF15), which are RNA-binding proteins involved in transcription and splicing, with different members of the ETS (E25-specific) family of transcriptional factors which are involved in cell

proliferation, cell differentiation, cell-cycle control, angio- genesis and apoptosis-most commonly FLI1 (85% of cases) [10]. The resulting chimeric fusion proteins act as aberrant transcription factors, causing tumor by deregulation genes involved in cell-cycle regulation, cell migration and pro- liferation.

Well-known genetic translocation of Ewing sarcoma is a recurrent balanced chromosomal translocation, most com- monly t(11;22)(q12;q24). This translocation results in the fusion gene of EWSR1 with FLI1. Among the 10 to 15%

of Ewing sarcoma cases negative for EWSR1-FLI1 fusions, other fusions occur, mainly between EWSR1 and ERG. With a lower frequency, ETV1, ETV4, FEV fusions to EWSR1 were identified (Fig. 1).

Cytogenetic and genomic studies identified recurrent

chromosomal abnormalities in Ewing sarcoma [11]. Chro-

mosome 1q gain and possibly chromosome 16q loss was

reported to be related with poor clinical outcome of Ewing

sarcoma [11,12]. Aberrant transcription can be induced by

various FET-ETS gene fusions. A recent study has shown

that gene transcription mediated by EWSR1-FLI1 leads to

the frequent formation of R loops, which are three-standard

structures composed of a DNA:RNA hybrid and an non-

template single-stranded DNA. These R loops might sensi-

tize Ewing sarcoma cells to poly (ADP-ribose) polymerase

(PARP) inhibitors, by synthetic lethality [13]. In addition,

epigenome profiling showed that EWSR1-FLI1 drives epi-

genetic reprogramming by inducing de novo enhancers and

by repressing enhancers in many mesenchymal origin cells

[14].

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Fig. 2. Radiological presentation of Ewing sarcoma. X-ray shows osteo- lytic lesion of bone and involvement of the periosteal tissue (A).

MRI scan showing primary tumor in the humerus and accompanying soft tissue edema (B). CT scan of the lungs show lung metastasis with pleural effusion of right lung (C).

Bone scintigraphy highlighting Ewing sarcoma in the humerus (D).

Diagnosis

1) Clinical features

Majority of patients present with a history of locoregional pain, which may be intermittent. In a substantial number of patients, pain is followed by a palpable soft-tissue mass.

About 20% of patients present fever, which increase the risk of tumor mistaken for osteomyelitis [15]. Median length of symptom before diagnosis is 3-9 months, however, time to diagnosis is not associated with presence of metastasis or outcome [16]. Ewing sarcoma most commonly involves the lower extremity, with the pelvis being the next most com- mon site. In long bones, Ewing sarcoma is generally of dia- physeal origin. Additionally, tumor sites vary with age; re- cent study showed that older AYA patients (20-24 years) had more pelvic and axial primary tumors, larger tumors and worse outcomes than children (0-9 years) [17]. In addi- tion, Ewing sarcoma in older patients tend to occur in soft tissues [18].

2) Diagnostic evaluation

Tumor imaging and metastatic evaluation of Ewing sarco- ma include initial radiological evaluation of affected bone, and successive CT of the lungs and bone scintigraphy for detection of metastases (Fig. 2). On radiographs, Ewing sar- coma show tumor-related osteolysis as a destructive mass of diaphyseal-metaphyseal bone with a multilayered ap- pearance. MRI provides better images to evaluate the extent of disease. 18F-fluorodeoxyglucose (FDG) PET-CT can be used to determine the presence of metastasis, including the metastases in the bone marrow [19]. Some studies sug- gested that FDG PET-CT may be sufficient for initial screen- ing of bone marrow metastases in Ewing sarcoma [20,21].

3) Pathology

Histologically, Ewing sarcoma has a solid pattern of

growth and is composed of monomorphic small round cells

with round nuclei [7]. The chromatin is stippled, and nucle-

oli are usually not observable. CD99 is a cell-surface glyco-

protein which considered a relevant diagnostic marker for

Ewing sarcoma [22]. Ninety-five percent of Ewing sarcoma

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specimen present strong, diffuse membranous expression of CD99, but CD99 is not specific for Ewing sarcoma and occurs in a large group of normal tissues, other small round cell tumors and lymphoblastic lymphoma. Currently, diag- nosis of Ewing sarcoma can be confirmed only by molec- ular pathology, with fluorescence in situ hybridization (FISH) and/or reverse transcription PCR (RT-PCR). In some patients, next-generation sequencing (NGS) or RNA se- quencing for rare gene fusions can be needed [23].

4) Risk classification

Metastatic status at diagnosis is the strongest prognostic factor of Ewing sarcoma. Approximately 10-30% of patients present metastases at the time of diagnosis. Common meta- stasis sites are lung (38%), bone (31%), and bone marrow (11%). Five-year overall survival (OS) remains ＜30% for patients with metastatic disease at diagnosis. However, those with isolated pulmonary metastasis shows better clin- ical outcome with OS of ∼50% [24-27]. According to a Korean single center retrospective study, 5-year OS rate of adult and children Ewing sarcoma patients was 33% [28].

Other single center study showed the 5-year OS rate of lo- calized Ewing sarcoma (N=76) was 58.9% [29].

The EUROEWING 99 R3 study of primary disseminated multifocal Ewing sarcoma identified additional prognostic factors (age at diagnosis ＞14 years, primary tumor volume

＞200 mL, presence and number of bone lesions, additional pulmonary metastases, and bone marrow involvement) [30].

In localized Ewing sarcoma, initial tumor size (＞8 cm) or volume (＞200 mL) is considered as a strong prognostic factor [31]. However, for localized tumors resected after in- duction chemotherapy, histologic response is the strongest independent prognostic factor [32-35]. Other reported prog- nostic factors include age, fever, and baseline lactate de- hydrogenase level [25,27,36].

Type of EWS-FLI family fusion has been reported as a prognostic factor at retrospective studies [37,38], but pro- spective evaluation found no prognostic impact of fusion transcript type [39,40]. Recurrent copy number variations (gain of chromosomes 1q, 8q, 20, and loss of chromosome 16q) has been reported as a possible prognostic relevance [41]. Also, poor prognostic value of concurrent STAT2 and

TP53 mutations has been reported [11].

Management

1) Treatment

Before the introduction of systemic chemotherapy, Ewing sarcoma had a cure rate of less than 10%, even in patients with localized disease [42]. Currently, patients with newly diagnosed Ewing sarcoma are treated with a combination of multi-agent cytotoxic chemotherapy and local control meas- ures (surgery and/or radiotherapy). Induction chemothe- rapy is given before local treatment to reduce the size of the primary tumor and address micrometastatic disease [43].

Currently, surgical resection is considered superior to de- finitive radiotherapy for local control [31,44,45]. Thus, tu- mor resection is performed whenever a marginal or wide resection seems possible. Definitive radiotherapy is only recommended for inoperable lesions, with a recommended dose of 54 to 55 Gy to the tumor with a 2 cm security mar- gin [46]. Postoperative radiation therapy is advised in cases of incomplete surgical resection; however, in Europe, pa- tients with poor histologic response to induction chemo- therapy also receive postoperative radiation therapy al- though tumor is completely resected [33,47].

An intergroup study conducted by the Pediatric Oncolo-

gy Group and the Children’s Cancer Group demonstrated

that the addition of ifosfamide and etoposide to cyclo-

phosphamide, doxorubicin, and vincristine significantly im-

proved outcomes for patients with localized Ewing sarcoma

[27]. In a subsequent trial, the Children’s Oncology Group

studied the value of dose intensity by comparing 3-weekly

versus 2-weekly (compressed) regimens of vincristine, dox-

orubicin and cyclophosphamide alternating with ifosfamide

and etoposide. The 5-year event free survival (EFS) was

better in patients who received the compressed regimen

(73% versus 65%) [48]. Another cooperative group clinical

trial, Euro-Ewing 99 showed that intense induction chemo-

therapy with VIDE (vincristine, ifosfamide, doxorubicin and

etoposide) followed by cyclophosphamide-based or ifosfa-

mide-based consolidation chemotherapy resulted in no dif-

ference of survival [49]. Alternation of both agents may be

a means to reduce cumulative doses of each and their late

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Table 1. Currently ongoing randomized trials for Ewing sarcoma

Name of study Subject Treatment scheme Study no.

COG AEWS1031 Localized 1) VDC/IE

2) VDC/IE+CPM/Topotecan NCT01231906

Ewing 2008 Localized, standard risk

1) 8 VAC/VAI

2) 8 VAC/VAI+zoledronic acid

NCT00987636 (localized, high risk published) Lung-only metastasis 6 VIDE+1 VAI → 7 VAI+lung RT → busulfan+melphalan

Other metastasis 6 VIDE → 8 VAC → Treosulfan/melphalan+8 VAC Euro-Ewing 2012 Localized or

lung-only metastasis

6 VIDE → 8 VAC → 8 VAC+zoledronate

5 VDC+4 IE → 3 VC+4 IE → 3 VDC+4 IE+zoledronate

ISRCTN 92192408 Italy ISG/AIEOP EW-1 localized Arm A: conventional dose

Arm B: dose-intensification and shorter length of treatment

NCT02063022

COG AEWS1221 Metastatic 1) VDC/IE

2) VDC/IE+ganitumab

NCT02306161 VITA

(Multicenter, Ph3)

Relapsed/refractory 1) Temozolomide+irinotecan

2) Temozolomide+irinotecan+Vigil (shRNAfurin and GMCSF augmented autologous tumor cell immunotherapy)

NCT03495921

effects, which is tested by ongoing long-term comparison

study.

High dose busulfan and melphalan (BuMel) improved EFS and OS when given after vincristine, ifosfamide, doxor- ubicin, and etoposide induction in localized ES with predeﬁ ned high-risk factors. Recent Euro-Ewing 99 and EWING- 2008 trial showed benefit of high dose busulfan and mel- phalan chemotherapy followed by autologous hemato- poietic stem cell transplantation compared to VAI (vincris- tine, dactinomycin, and ifosfamide for 7 cycles) in high-risk localized Ewing sarcoma patients (poor histologic response after 6 cycles of VIDE, large tumor ＞200 mL) [50].

Early studies in Ewing sarcoma with lung metastasis showed that whole lung irradiation (WLI) could improve the 5-year EFS when compared to no WLI (49% versus 36%) [51]. Later, a collaborative European and US trial com- pared treatment with chemotherapy of vincristine, dactino- mycin and ifosfamide plus WLI and high-dose BuMel che- motherapy by randomization. The trial showed no differ- ence between the two treatment, with 3-year EFS of 51%

and 55%, respectively [25].

When Ewing sarcoma recurs after initial therapy, the prognosis is very poor, with less than 5% of patients re- maining alive more than 2 years following recurrence [52,53]. Several chemotherapy regimens showed activity in relapsed Ewing sarcoma; cyclophosphamide with top- otecan, irinotecan with temozolomide, gemcitabine with

docetaxel, and high dose ifosfamide [54-57].

Strategies under clinical investigation in Ewing sarcoma include the use of PARP inhibitors as enhancers of drug sensitivity in combination with agents such as trabectedin and/or temozolomide [58,59]. Insulin-like growth factor-1 receptor (IGF1R)-blocking antibodies or small-molecule in- hibitors produced some transient report in few patients, but was dropped because of failure to prolong the effectiveness as a single-agent treatment. Children’s Oncology Group is processing (recruiting) on a randomized trial with and with- out IGFR1 antibody, in combination with VDC-IE chemo- therapy in metastatic Ewing sarcoma. (NCT02306161) More- over, targeting the epigenetic deregulation by inhibitors of lysine-specific histone deacetylase 1A, histone deacetylase, and DNA methyltransferase are on studies [60-62]. These new trials are potentially expected to advance the outcome of Ewing sarcoma (Table 1).

2) Quality of life

Patients with Ewing sarcoma are at risk of substantial dis- ease-related and therapy-related late sequelae. Long term follow up report by Childhood Cancer Survivor Study (CCSS) described chronic health impairment in 70% of sur- vivors of Ewing sarcoma at 35 years after diagnosis [63].

All local treatment modalities can increase the risk of

long-term neuromusculoskeletal complications, reduced

functional capacity [64-66]. However, recent study showed

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that, on average, recommended level of active lifestyle was achieved in Ewing sarcoma survivors [67]. Chemotherapy regimens used in Ewing sarcoma usually adopts anthracy- clines, alkylating agents and etoposide. Cardiomyopathy, renal impairment, renal Fanconi syndrome and infertility have been described [63]. Furthermore, second malignancy is a concern, which was reported to occur in ∼9% of Ewing sarcoma survivors [68]. Etoposide and high-dose chemotherapy were identified as risk factors for second ma- lignancy [68]. Radiotherapy is also well known as risk factor for second malignancy, especially osteosarcoma, acute myeloid leukemia, breast cancer and thyroid cancer [69].

Conclusion

Multimodality treatment improved the outcome of Ewing sarcoma, but survival rate of patients with metastatic or re- current Ewing sarcoma still remain poor. Risk-directed ther- apy and efforts for developing novel therapeutic ap- proaches based on understanding of molecular mechanisms are needed to improve the outcome of Ewing sarcoma and to lessen the treatment-related late effects.

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