Dose response and local control using radiotherapy in non-metastatic ewing sarcoma

Background. To determine prognostic factors for local control in the radiotherapeutic management of non-metastatic Ewing sarcoma. Procedure. Forty patients with localized Ewing sarcoma (ES) were treated with primary site RT at one institution. Median RT dose was 55.8 Gy (range, 25.5-76 Gy). Chemotherapy was given to 34 patients (85%) with the most common regimen being vincristine, dactinomycin, cyclophosphamide, doxorubicin alternating with ifosfamide and etoposide (VACA + IE) in 10. Median follow-up for surviving patients was 12.3 years (range, 1.7-26.4 years). Results. The 5- and 10-year local control rate was 78.2%. On multivariate analysis, RT dose was the only prognostic factor to impact on local control. The 5- and 10-year local control rate was 88.7% for RT dose ≥49 Gy and was 37.5% for <49 Gy (P = 0.0002, log-rank test). For tumors ≤8 cm, the 5- and 10-year local control rate was 94.1% for RT dose ≥49 Gy and 50.0% for RT dose <49 Gy (P = 0.01, log-rank test). For tumors >8 cm, the 5- and 10-year local control rate was 85.7% for RT dose ≥54 Gy and 26.7% for RT dose <54 Gy (P = 0.006, log-rank test). Conclusions. Radiotherapy dose was found to influence local control in ES. In particular, patients who received RT doses ≥49 Gy for tumor size ≤8 cm and ≥54 Gy for tumor size >8 cm had improved local control.