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

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.