Differences in intraosseous and extraosseous post-chemotherapy regression of Ewing sarcomas and their influence on prognosis.

ABSTRACT

BACKGROUND: In Ewing sarcomas (ES), histological response to polychemotherapy is the main prognostic factor. We aimed at evaluating the histological response separately for the extraosseous and intraosseous tumor compartment as well as its prognostic influence. METHODS: Thirty-one patients with ES and marked soft tissue expansion, treated at our department between January 2006 and December 2015, were retrospectively included. Data was taken from medical records. Original histologic specimens of the resected tumors were re-evaluated separately for intra- and extraosseous tumor regression according to Salzer-Kuntschik regression grading. Multivariate survival analysis with stepwise backward variable selection was calculated to determine the impact of extraosseous and intraosseous regression on prognosis. RESULTS: All patients had received chemotherapy, 15 (48.4%) had been administered preoperative radiotherapy. Extraosseous tumor regression was significantly worse than intraosseous regression (Wilcoxon signed-rank test, p = 0.018). While neither intraosseous nor extraosseous tumor regression had an impact on overall survival, extraosseous complete remission had a beneficial impact on event-free-survival in the multivariate analysis (Cox-regression; hazard ratio 0.148, 95% confidence interval 0.031-0.707, p = 0.017). CONCLUSIONS: On average, regression of ES seems to be worse in the extraosseous tumor compartment following preoperative chemotherapy. Moreover, extraosseous tumor regression may have a stronger prognostic influence on event-free survival than intraosseous regression.