Ewing sarcoma of the pelvis: Clinical features and overall survival

Introduction: Primary Ewing Sarcoma of Bone is a malignancy whose treatment requires both systemic chemotherapy and local control through surgical resection and/or radiation. Ewing Sarcoma of the pelvis has been noted to confer a worse prognosis relative to other anatomic sites of Ewing Sarcoma. This study explores the presenting features, treatment modalities for local control, and overall survival of primary Ewing sarcoma of the pelvis in comparison to other commonly affected anatomic sites.

Methods: The National Cancer Institute Surveillance, Epidemiology, and End-Results (SEER) database was used to identify cases of pelvic Ewing sarcoma diagnosed between years 2004 and 2015. Demographic variables including sex, race, and age at diagnosis were described for each case, as well as therapeutic modalities including surgery and radiation. Bone-specific Collaborative Staging variables, including tumor size, tumor extension, and metastasis at diagnosis, were described for the same cohort. Univariate and multivariate assessments were performed for statistical comparison between presenting factors, treatment modalities, and between anatomic locations of presentation.

Results: Within the database, 296 patients with Ewing sarcoma of the pelvic bones were available for review, which represented 25.7% of the 1152 cases surveyed across all anatomic sites. In the subset of patients with Ewing Sarcoma of the pelvis, 63.5% were male; the median age of diagnosis was 17 years; extra-compartmental tumor extension was noted in 82.1%; average tumor size was 9.7 cm; and metastasis at diagnosis was noted in 46.1% of the cohort. Only 28.6% of the pelvis sarcoma patients received surgical resection as part or all of their local control treatment, while 67.6% received some form of radiation therapy. When compared to the presenting features of Ewing Sarcoma from other anatomic sites, patients with pelvic tumors had larger tumors at time of diagnosis, higher rates of metastatic disease, and were less likely to undergo surgical intervention. The 2-, 5-, and 10-year overall survival rates for the patients presenting with Ewing Sarcoma of the pelvis was 70.3%, 49.7%, and 41.9%, respectively, which were significantly lower across all time-points than any other anatomic site.

Discussion and conclusion: Ewing Sarcoma of the pelvis is an aggressive malignancy that presents with relatively large tumors and a high rate of metastatic dissemination. Surgical intervention is less frequent when Ewing Sarcoma presents in the pelvis than when it presents in other anatomic locations. These factors may contribute to the worse overall survival of Ewing Sarcoma when compared to the same diagnosis originating in other anatomic sites. Prospective, randomized study is required to determine the true causal effects of these factors on survival.