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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 6  |  Issue : 1  |  Page : 1-7

Extraosseous ewing sarcoma: Experience from a tertiary cancer institute in South India


Department of Medical Oncology, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka, India

Date of Submission08-Jun-2021
Date of Decision06-Mar-2022
Date of Acceptance07-Mar-2022
Date of Web Publication20-Apr-2022

Correspondence Address:
Linu Abraham Jacob
Professor and Head of Department, Department of Medical Oncology, Kidwai Memorial Institute of Oncology, Bengaluru - 560029, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/oji.oji_23_21

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  Abstract 


Background: Extraosseous Ewing sarcoma (EOES) is the rare soft-tissue counterpart of Ewing sarcoma (ES) of bone. However, studies on clinical behavior and outcome of EOES are scarce. In this retrospective study, we described the pattern of clinicodemographic characteristics, treatment, and outcomes of EOES and explored predictors of outcomes. Materials and Methods: A total of 46 diagnosed EOES patients were treated at our institute from September 2017 to January 2020. The detailed data were retrieved from hospital records and were analyzed. Progression-free survival (PFS) was estimated by the method of Kaplan and Meier curve. Comparison of different parameters for PFS was calculated by using log-rank test. Results: The mean age at diagnosis was 29.6 years with a male-to-female ratio of 1.4:1. The most common primary site of location for EOES was lower limb (n = 14), followed by retroperitoneum (n = 13) and trunk (n = 10). Seven (15.2%) patients presented with upfront metastasis and the rest 39 cases were nonmetastatic. Treatment outcome was evaluated in 43 patients (38 nonmetastatic and 5 metastatic) in terms of median PFS (mPFS). Extremity EOES in comparison to nonextremity (axial) EOES (P = 0.030) and localized versus upfront metastatic EOES (P = 0.001) had better mPFS. The localized EOES patients who received surgical treatment approach had higher mPFS than those who received nonsurgical treatment (18 months versus 14 months; P = 0.009). EOES patients with subcutaneous (SC) lesions had a trend of higher mPFS than other patients (19 months versus 15 months; P = 0.055). We did not find any difference in mPFS for gender and size of the tumor at presentation. Conclusions: Lower limb and retroperitoneum are the common primary sites of presentation for EOES. EOES patients with extremity location, SC lesion in comparison to deeper presentation, upfront nonmetastatic, and those receiving surgical treatment approach performed better.

Keywords: Chemotherapy, clinical profile, extraosseous Ewing sarcoma, progression-free survival, surgery


How to cite this article:
Sai RK, Lokesh K N, Dasappa L, Babu M C, Rajeev L K, Jacob LA. Extraosseous ewing sarcoma: Experience from a tertiary cancer institute in South India. Oncol J India 2022;6:1-7

How to cite this URL:
Sai RK, Lokesh K N, Dasappa L, Babu M C, Rajeev L K, Jacob LA. Extraosseous ewing sarcoma: Experience from a tertiary cancer institute in South India. Oncol J India [serial online] 2022 [cited 2022 Aug 18];6:1-7. Available from: https://www.ojionline.org/text.asp?2022/6/1/1/343571




  Introduction Top


Ewing sarcoma family of tumors (ESFTs) include several subtypes of tumors, including classical Ewing tumors, atypical Ewing tumors, Askin tumors of the chest, and peripheral primitive neuroectodermal tumors (PNETs).[1] Majority of Ewing sarcoma (ES) cases are of skeletal system origin, and extraosseous ES (EOES) is relatively a rare occurrence.[2] Being EOES of soft-tissue origin, the commonly located sites include paravertebral spaces, lower extremities, head and neck, and pelvis. Retroperitonium, omentum, orbit, skin, and chest wall are the other rare sites of location for EOES.[2]

Due to relatively rare entity, the clinical behavior and optimal treatment strategies for EOES are less known than osseous ES. Few studies show better[3],[4] outcome of EOES compared to skeletal ES, while some studies show similar[5],[6],[7],[8],[9],[10] prognosis of EOES to skeletal ES. Over the past few decades, major improvements in outcomes of patients with EOES have been achieved through multimodality treatment approaches, as shown by various trials.[2],[3],[4],[11] Clinical presentation, prognosis, and outcome depend on the site of origin of EOES, stage of disease at presentation, and multimodality approaches of treatment. The prognostic impact of tumor stage, size, site, and age at diagnosis are more studied on ES of bone. Only a few studies have evaluated EOES for the clinical profile and outcome.[3]

The present retrospective analysis describes the clinical profile, treatment details, and outcome of EOES patients who received treatment in our institute along with literature review.


  Materials and Methods Top


The present retrospective study was conducted on diagnosed EOES patients over a period from September 2017 to January 2020. The patients who attain our Tertiary care cancer institute at Bangalore either receiving treatment or under follow-up after completion of treatment were included. The detailed demographic and clinical profile data, imaging findings, and treatment details were retrieved from the medical records.

The patients were investigated by routine blood test (hemogram and biochemistry), contrast magnetic imaging resonance (MRI) scan of local part, and another staging workup including contrast-enhanced computed tomography scan of neck/thorax/abdomen/pelvis or positron emission tomography–computed tomography (PET-CT) scan of whole body. Tissue diagnosis was made by tru-cut or core needle biopsy for histopathologic examination and immunohistochemical examination. Molecular genetic study was done to identify chromosomal translocation, t (11;22) by conventional cytogenetics, or FISH for EWSR1-FLI1 fusion gene.

Patients were treated with multimodality of treatment, particularly for localized diseases such as different permutations of neoadjuvant chemotherapy (NACT), surgical excision, adjuvant chemotherapy, and radiotherapy. Palliative chemotherapy or radiotherapy was used particularly in patients presenting with metastatic disease. The chemotherapy regimens used were VAC and IE. VAC regimens consisted of vincristine 1.4 mg/m2 (maximum dose = 2 mg) plus adriamycin 75 mg/m2 or actinomycin D 1.25 mg/m2 plus cyclophosphamide 1200 mg/m2 with mesna on day 1, and the cycle was repeated at 3-weekly intervals. IE regimen consisted of ifosfamide 1.8 g/m2 and etoposide 100 mg/m2 on day 1 to day 5, and the cycle was repeated at 3-weekly intervals. VAC and IE regimens are used alternatively for 9–12 weeks as neoadjuvant treatment, followed by definitive local treatment and adjuvant treatment depending upon surgical status for a maximum of 17 cycles. Radiotherapy was given in either as adjuvant or after NACT or in palliative settings as per the disease status. Definitive local treatment includes surgery or radiotherapy.

At the end of treatment, patients were followed up every 3–6 monthly with physical examination for 2–3 years and then annually. During follow-up, imaging evaluation was done such as chest imaging every 6–12 months by CT chest or X-ray and imaging of primary site based on estimated risk of locoregional recurrence by MRI or CT contrast.

Statistical analysis

Statistical analysis was done using IBM SPSS Statistics for Windows, Version 20.0. IBM, Armonk, New York, US. Progression-free survival (PFS) was calculated during the study period. PFS is defined as the time interval from date of diagnosis to date of first event (relapsed or progressive disease, second malignancy, or death from any cause) or to date of last contact for patients without events. Kaplan–Meier analysis was done to determine the PFS, and median PFS (mPFS) was calculated along with its 95% confidence interval. Log-rank test was used to compare PFS among different groups. P ≤ 0.05 was taken as statistically significant.


  Results Top


During the study period, a total of 46 patients diagnosed with EOES were retrieved from the medical records. The patients' demographic and clinical profiles are depicted in [Table 1]. The mean age at diagnosis was 29.6 years (range: 15–68 years). There was a male predominance with a male-to-female ratio of 1.4:1. The most common site of the primary tumor was the axial (nonextremity) location (n = 30; 65.3%) followed by extremities (n = 16; 34.7%). The anatomical subsites of EOES are depicted in [Table 2]. Overall, the most common subsite of EOES was lower limb (n = 14), followed by retroperitoneum (n = 13) and thorax or trunk (n = 10). The most common presenting symptom was swelling (n = 27; 58.7%), followed by pain (n = 15; 32.6%). Other rare presenting symptoms were difficulty to walk (n = 3), shortness of breath (n = 2), constipation (n = 2), and urinary complaints (n = 2) depending on the site of involvement. According to histopathology, we found 41 (89.1%) patients as ES and 5 (10.9%) patients as PNET variant for ESFT. Seven (15.2%) patients presented with upfront metastatic disease most commonly to lung (n = 3), followed by liver (n = 2) and bone (n = 2), while the remaining 39 (84.8%) patients presented with localized nonmetastatic disease. Patients were treated with multimodality treatment approach depending on their stage at presentation.
Table 1: Demographic and clinical characteristics of extraosseous Ewing's sarcoma patients

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Table 2: Primary site of origin of extraosseous Ewing's sarcoma patients

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Out of 39 localized EOES patients, 10 patients underwent upfront surgery in the form of wide local excision (WLE). Surgical resection margin was positive in six patients. All the ten patients received adjuvant chemotherapy, and all R1 resection patients (n = 6) received adjuvant radiotherapy. The rest 29 patients received NACT as a VAC regimen alternate with IE. Fourteen out of these 29 patients after NACT were able to undergo surgery due to adequate response to NACT. Among these 14 patients, WLE was performed in 12 patients, in which surgical resection margin was found to be negative in seven patients and positive in the rest five patients. The rest two patients underwent decompression surgery due to paraspinal location of EOES. These 14 patients were further subjected to adjuvant chemotherapy ± radiotherapy. Two patients progressed on adjuvant treatment as lung metastasis in one and local recurrence with lung metastasis in another patient. These two patients were put on palliative chemotherapy. The rest 15 out of 29 patients could not undergo surgery because of poor response or noncompliance to NACT and were subjected to further chemotherapy and/or local treatment as radiotherapy. Five patients received radiotherapy as local treatment and the rest ten patients continued chemotherapy till progression. Four out of these 15 patients progressed during treatment such as lung metastasis in two patients, liver in one patient, and bone metastasis in one patient. Hence, these four patients were put on palliative chemotherapy and palliative radiotherapy was given to patients with bone metastasis.

Upfront metastatic EOES was detected in seven patients, and these patients received chemotherapy with VAC regimen as palliative intent. Those with bone metastasis (n = 2) received palliative radiotherapy followed by palliative chemotherapy. Two out of seven patients progressed during treatment to lung metastasis in one patient and bone metastasis in one patient. These two patients were put on palliative chemotherapy with IE regimen, and palliative radiotherapy was given to patients with bone metastasis.

Forty-three out of 46 patients of EOES were evaluated for response assessment as three patients (2 upfront metastatic and 1 localized) could not complete the treatment at the time of data analysis so excluded from assessment. Thirty-five patients had response to treatment which included complete response (n = 10), partial response (n = 2), and stable disease (n = 23), while the rest eight patients showed progressive disease during treatment, as shown in [Table 3].
Table 3: Response assessment (n=43)

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The factors predicting outcome of EOES in terms of mPFS are analyzed in [Table 4]. Different factors analyzed were gender, anatomical site, deeper presentation, size of the tumor, stage of presentation, and treatment approach.
Table 4: Prediction of factors for survival outcomes (n=43)

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We did not find a significant difference of mPFS between male and female gender EOES patients (P = 0.343). Extremity EOES had better PFS as compared to nonextremity EOES with mPFS of 19 versus 13 months, as shown in [Figure 1]. The difference in PFS between these two groups was found to be significant (P = 0.030). We did not find a difference in mPFS between patients with tumor size ≤8 cm versus >8 cm (P = 0.338) [Table 4].
Figure 1: Kaplan–Meier curve showing progression-free survival between extremity extraosseous Ewing sarcoma and nonextremity extraosseous Ewing sarcoma

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In our analysis, five patients presented with subcutaneous (SC) lesion and the exact site of these SC lesion on presentation are one case each for neck, vulva, Brachial plexus, thigh and forearm. Four patients underwent WLE with R0 resection followed by received adjuvant chemotherapy to all the cases, and all patients had CR at the end of treatment, while the rest one case of brachial plexus EOES received chemotherapy alone and had stable disease at the end of the treatment. SC EOES had a trend of better PFS as compared to non-SC EOES patients with a mPFS of 19 versus 15 months although statistically not significant (P = 0.055), as shown in [Figure 2].
Figure 2: Kaplan–Meier curve showing progression-free survival between subcutaneous extraosseous Ewing sarcoma and nonsubcutaneous extraosseous Ewing sarcoma

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Patients with localized or nonmetastatic EOES had better mPFS as compared to metastatic EOES (16 months versus 8 months; P = 0.001), as shown in [Figure 3]. The PFS in localized disease was higher among patients who had undergone surgical treatment approach (surgery + chemotherapy ± radiotherapy) than those receiving nonsurgical treatment with a mPFS of 18 months vs. 14 months (P = 0.009), as shown in [Figure 4].
Figure 3: Kaplan–Meier curve showing progression-free survival between localized and metastatic extraosseous Ewing sarcomas

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Figure 4: Kaplan–Meier curve showing progression-free survival between surgical versus nonsurgical treatment approach

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Overall, 6 out of 39 localized EOES patients and 2 out of 7 upfront metastatic patients progressed during treatment. Those who progressed on VAC/IE regimen chemotherapy later started on second-line chemotherapy IE regimen as palliative intent until progression. However, all the patients were alive during the study analysis.


  Discussion Top


EOES is a rare tumor with different clinical characteristics and outcomes as compared to its bone counterpart.[3],[4] As per the published series, the incidence of EOES may vary from around 8%–43%.[1],[3],[5],[10],[11] There are very few studies examining EOES and its clinical behavior, optimal treatment, and outcome. In this study, we included 46 patients of EOES treated at our institute. All the patients were studied for clinical characteristics including age, sex, PS, histology, size, grade, site of disease, and pattern of presentation of EOES, while 43 patients out of these were analyzed for treatment outcomes as three patients are still on treatment.

The age of presentation for EOES is higher than that of ES of bone.[3],[5] The mean age at diagnosis in our study was 29.6 years which was supported by the published literature. EOES most likely arise from axial location.[3],[12] El Weshi et al.[9] reported trunk as the predominant location for EOES. Applebaum et al. reported that although axial location is the most common site of EOES, pelvic primary is less likely.[3] In our analysis also, the most common site of EOES is axial location followed by extremity EOES. However, in some published reports, extremity location was frequently observed for EOES.[13],[14],[15] Hence, the predominant site of primary location for EOES is not clear. EOES patients presented more PNET histology types among ESFT in comparison to osseous ES. Esen et al.[1] in their study reported that typical ES was seen in 86.2% of EOES cases, whereas only 10.3% of EOES cases were atypical ES. In our study, we also found PNET histology in a smaller number of EOES cases than classical ES histology, whereas Applebaum et al.[3] reported PNET (58.3%) as the most common histology for EOES followed by ES (41.7%). According to some studies, EOES patients presented as a smaller tumor compared to skeletal ES, whereas few studies found no difference.[3],[4],[6],[12],[16] In the present study, a greater number of EOES patients presented with larger tumor size (>8 cm) than ≤8 cm size. The site of distant metastatic spread may be different in osseous ES and EOES. Lung is the most common site for distant metastasis in both the entities. Bone is the second common site of distant metastasis in osseous ES, whereas it was liver in cases of EOES.[1] However, a study by Huh et al.[17] reported lymph node as the most common site of metastasis, followed by lungs, bones, solid organs, peritoneum, and pleura in EOES patients, but the authors did not include lymph node as a site of distant metastasis. Lung is the most common site of distant metastasis in our study which is supported by other published literatures.[1]

Only a few studies had investigated the optimal treatment approach for EOES. As per prior study or literature review, the treatment of any member of ESFT should be based on the same principle as applied for skeletal ES.[18] Hence, EOES patients, especially in nonmetastatic settings, require a multidisciplinary approach integrated by local (surgery and/or radiotherapy) plus systemic treatment (chemotherapy) with more or early role of surgical excision with negative margin as compared to bone ES.[3],[4],[19],[20]

The extents of negative surgical margins do not influence local control; hence, the goal of surgical resection in ESFT is to achieve a three-dimensional tumor-free surgical margin.[21] NACT and delayed resection increase the likelihood of complete surgical removal of tumor with negative margins, and hence, RT can be avoided.[22] In our study, 10 out of 39 localized EOES patients underwent upfront surgery and 60% of cases had surgical margin positive, whereas only 40% of cases had negative margin. The rest 29 patients received NACT, and surgery was able to perform in 48.3% (14/29) of cases, in which 2 cases underwent only decompression due to paravertebral location. Hence, out of the rest 12 cases, surgical resection margin negative was seen in 58.3% of cases and margin positive was seen in 41.7%. Hence, we also find an increase likelihood of margin-negative surgery after NACT than those who had undergone upfront surgery although significant difference could not be established due to less number of patients who underwent surgery. Bacci et al.[23] reported comparable results between NACT and adjuvant CT for localized ESFT patients. Other published literature (Castex et al.) stated that adjuvant chemotherapy improves overall survival rates and decreases the tumor recurrence probability.[6]

Over the several past decades, the role of radiation therapy for ES has been studied. Applebaum et al.[3] reported more RT use in skeletal ES than EOES. However, over time, the use of RT has been diminished and the reason for this change is not clear which needs further evaluation. In our retrospective analysis, adjuvant RT was less used in margin-negative cases, whereas it was given to all margin-positive cases. Vogin et al. reported the importance of preoperative RT for successful local treatment in spinal ES patients.[24]

Two prospective studies by Granowetter et al.[25] and Castex et al.[6] reported similar outcomes for EOES patients who followed the principles of ES protocol. Livellara et al.[26] in a retrospective cohort reported a satisfactory outcome in terms of 10-year event-free survival (77.5%) and overall survival (85.5%) in localized EOES patients treated with a tailored approach derived from soft-tissue sarcoma protocols, which was less intensive and shorter when compared to protocols used in the management of skeletal ES. Applebaum et al.[3] in a US SEER database from 1973 to 2007 reported a significant difference in treatment strategies and outcomes for EOES as compared to skeletal ES. They found superior overall survival (P = 0.02) in localized disease for EOES patients than skeletal ES. These SEER data stated that EOES entity requires additional effort to determine optimal treatment strategies for better outcomes.

Patients receiving local therapy as surgery or radiotherapy along with chemotherapy had better response rate and PFS as compared to chemotherapy alone.[3],[4],[6],[13],[14],[19] In our analysis, patients undergoing surgery either upfront or after NACT had better mPFS compared to those receiving chemotherapy without surgery (18 vs. 14 months; P = 0.009) which is on par with prior studies. A retrospective analysis on 42 EOES patients without bony involvement by Rud et al.[14] at Mayo Clinic reported a 5-year OS of 38.5% and found that those patients with R0 resection, extremity EOES, and receiving multimodality treatment had a better survival outcome, whereas those having incomplete resection (R1), pelvic EOES, and presence of metastasis had decreased survival. Another retrospective analysis of 24 patients by Ahmad et al.[19] found that those receiving surgical treatment approach had better outcome in terms of OS and DFS (P < 0.05) than those who underwent no attempt at surgical resection.

In our study, patients with extremity EOES had better response rate in terms of mPFS as compared to nonextremity EOES (19 vs. 13 months; P = 0.030) which is on par with prior studies. Similar outcome was seen in a retrospective analysis by Rud et al.[14] at Mayo Clinic showing better outcome in terms of 5-year OS in extremity EOES as compared to pelvic EOES. The most probable reason for better outcome in patients with Extremity EOES could be higher chances of adequate surgical resection with negative margin as compared to pelvic or axial/Non extremity EOES. Patients with localized disease had better survival outcome as compared to those with metastatic EOES.[14] Upfront detection of metastasis at diagnosis is the strongest adverse prognostic factor.[27] We also found higher mPFS in EOES patients who have no upfront distant metastasis than presence of upfront metastasis (16 months vs. 8 months; P = 0.001). Similar outcome was seen by Biswas et al.[4] in a retrospective analysis of 60 patients of EOES showing 5-year estimate of EFS and OS of 64.3% and 68.3%, respectively, in localized EOES, while 5-year estimate of EFS and OS was 15.8% and 43.9%, respectively, in metastatic EOES.

Patients who progressed on treatment are those with large initial tumor size (≥8 cm), having inadequate resection with residual disease, or those who default treatment, and the most common reason for progression or metastasis was patient noncompliance to treatment. Prognostic factors for EOES are nearly similar to osseous ES. EOES patients with SC lesions have a favorable outcome than patients with deeper lesions. Orr et al.[16] reported that patients with SC ESFT performed better survival at 15 years than other EOES patients (91.7 ± 9% vs. 47 ± 12%). They suggested that EOES patients with SC lesions were significant predictors of outcome. In our study, SC EOES patients had a trend of higher mPFS as compared to other EOES patients although difference is statistically not significant due to less number of patients for SC EOES. The reason of better survival in SC EOES may be due to more feasibility of surgical resection with negative margins. Although the number of patients with PNET is very small, we did not find any difference in outcome between PNET and typical ES.

All the patients in our study were alive at the time of analysis, with a median follow-up from diagnosis of 2 years (range: 1.3–2.5 years). The strongest predictor of outcome was tumor stage (metastatic versus nonmetastatic), the site of disease, and treatment approach of patients.


  Conclusions Top


The patients receiving multimodality treatment approach, i.e., both definitive surgery and chemotherapy, patients with extremity EOES, and patients with localized nonmetastatic EOES have a favorable outcome as compared to their counterpart when treated on ES treatment protocols.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Esen SA, Acikgoz Y, Bal O, Yildiz B, Ucar G, Dirikoc M, et al. A comparison of osseous and extraosseous Ewing sarcoma. J Coll Physicians Surg Pak 2021;31:27-33.  Back to cited text no. 1
    
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Applebaum MA, Worch J, Matthay KK, Goldsby R, Neuhaus J, West DC, et al. Clinical features and outcomes in patients with extraskeletal Ewing sarcoma. Cancer 2011;117:3027-32.  Back to cited text no. 3
    
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Biswas B, Shukla NK, Deo SV, Agarwala S, Sharma DN, Vishnubhatla S, et al. Evaluation of outcome and prognostic factors in extraosseous Ewing sarcoma. Pediatr Blood Cancer 2014;61:1925-31.  Back to cited text no. 4
    
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Lee JA, Kim DH, Lim JS, Koh JS, Kim MS, Kong CB, et al. Soft-tissue Ewing sarcoma in a low-incidence population: Comparison to skeletal Ewing sarcoma for clinical characteristics and treatment outcome. Jpn J Clin Oncol 2010;40:1060-7.  Back to cited text no. 8
    
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El Weshi A, Allam A, Ajarim D, Al Dayel F, Pant R, Bazarbashi S, et al. Extraskeletal Ewing's sarcoma family of tumours in adults: Analysis of 57 patients from a single institution. Clin Oncol (R Coll Radiol) 2010;22:374-81.  Back to cited text no. 9
    
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Salah S, Abuhijla F, Ismail T, Yaser S, Sultan I, Halalsheh H, et al. Outcomes of extra-skeletal versus skeletal Ewing sarcoma patients treated with standard chemotherapy protocol. Clin Transl Oncol 2020;22:878-83.  Back to cited text no. 11
    
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Cash T, McIlvaine E, Krailo MD, Lessnick SL, Lawlor ER, Laack N, et al. Comparison of clinical features and outcomes in patients with extraskeletal versus skeletal localized Ewing sarcoma: A report from the Children's Oncology Group. Pediatr Blood Cancer 2016;63:1771-9.  Back to cited text no. 12
    
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Siebenrock KA, Nascimento AG, Rock MG. Comparison of soft tissue Ewing's sarcoma and peripheral neuroectodermal tumor. Clin Orthop Relat Res 1996;329:288-99.  Back to cited text no. 15
    
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Orr WS, Denbo JW, Billups CA, Wu J, Navid F, Rao BN, et al. Analysis of prognostic factors in extraosseous Ewing sarcoma family of tumors: Review of St. Jude Children's research hospital experience. Ann Surg Oncol 2012;19:3816-22.  Back to cited text no. 16
    
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Huh J, Kim KW, Park SJ, Kim HJ, Lee JS, Tirumani SH, et al. Imaging features of primary tumors and metastatic patterns of the extraskeletal Ewing sarcoma family of tumors in adults: A 17-year experience at a single ñnstitution. Korean J Radiol 2015;16:783-90.  Back to cited text no. 17
    
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Casali PG, Bielack S, Abecassis N, Aro HT, Bauer S, Biagini R, et al. Bone sarcomas: ESMO-PaedCan-EURACAN clinical practice guidelines for diagnosis, treatment and follow-up. Ann Oncol 2018;29:v79-95.  Back to cited text no. 20
    
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Shamberger RC, LaQuaglia MP, Gebhardt MC, Neff JR, Tarbell NJ, Marcus KC, et al. Ewing sarcoma/primitive neuroectodermal tumor of the chest wall: Impact of initial versus delayed resection on tumor margins, survival, and use of radiation therapy. Ann Surg 2003;238:563-7.  Back to cited text no. 22
    
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Bacci G, Balladelli A, Forni C, Ferrari S, Longhi A, Bacchini P, et al. Adjuvant and neoadjuvant chemotherapy for Ewing sarcoma family tumors in patients aged between 40 and 60: Report of 35 cases and comparison of results with 586 younger patients treated with the same protocols in the same years. Cancer 2007;109:780-6.  Back to cited text no. 23
    
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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