M. Mirza1, A. Khan Yasinzai2, I. Khan2, U. Waqar1, A. Ullah3, H. Lovvorn1, A. Khan1, K. Idrees1 1Vanderbilt University Medical Center, Nashville, TN, USA 2Bolan Medical Complex Hospital, Quetta, PAKISTAN, Pakistan 3Texas Tech University Health Sciences Center, Lubbock, TX, USA
Introduction: Extraosseous Ewing sarcoma is a rare variant of Ewing sarcoma that primarily manifests within soft tissues (ST-EWS) but occasionally arises in visceral organs in chest, abdomen, and pelvis (V-EWS). The rarity of V-EWS has hindered our understanding of its unique clinical features and the development of effective management strategies. This study leverages a population-derived dataset to evaluate the clinical and pathological characteristics of patients diagnosed with V-EWS to those with Osseous EWS (O-EWS) and ST-EWS.
Methods: This retrospective cohort study employed data from the Surveillance, Epidemiology, and End Results program, encompassing all patients diagnosed with EWS from 2000 to 2018. Patient demographics, tumor characteristics, treatment modalities, and survival outcomes were analyzed. Prognostic factors were identified using Cox proportional hazards regression analysis.
Results: 2605 patients were identified. Most patients were diagnosed with O-EWS (71.1%), followed by ST-EWS (21.4%), and V-EWS (7.4%). Patients diagnosed with V-EWS tended to be older than 18 years, differing from those diagnosed with ST-EWS and O-EWS (74.7% vs. 59.1% vs. 40.2%, respectively; p=0.001). Patients with V-EWS most commonly metastasized to the liver and brain (3.6% V-EWS vs. 1.5% ST-EWS and 1.4% O-EWS; p=0.01) compared to ST-EWS Figure 1. Combination chemotherapy with surgery was the most common treatment modality for both V-EWS and ST-EWS. However, chemotherapy alone was more common in O-EWS than in the other two variants (35.8% in O-EWS, 23.5% in ST-EWS, and 24.7% in V-EWS). Multivariate regression analysis revealed that advanced age (HR 2.18, 95% CI 1.82-2.63), large tumor size (HR 1.63, 95% CI 1.35-1.95), and distant metastasis (HR 5.90, 95% CI 3.83-9.10) were all independent risk factors for mortality in patients with Ewing sarcoma. Although survival analysis revealed diminished overall survival rates for V-EWS patients compared to ST-EWS and O-EWS patients, V-EWS did not emerge to be an independent risk factor for mortality after adjusting for other clinical factors.
Conclusion: Our study establishes V-EWS as a distinct clinical entity, marked by unique clinicodemographic features and tumor characteristics. Notably, patients with V-EWS tended to be older compared to those with ST-EWS and O-EWS. Additionally, they exhibited a higher likelihood of presenting with liver and brain metastases. In conclusion, our population-based study underscores the critical significance of distinguishing between Ewing sarcoma subtypes and tailoring management strategies accordingly.
