Although the rate of severe toxicity was very low, the real impact of WLI on patients' outcomes remains unproven, probably due to the narrow dose limits that can be delivered to the whole lung parenchyma. New strategies to prevent or treat lung metastases in these patients should be tested. Ultra-fractionated radiotherapy concurrent with modern chemotherapy protocols could be tested in this setting due to the chemo-sensitizing effect and negligible radio-induced toxicity of fraction doses <0.5 Gy.

Purpose: To analyze toxicity and outcome predictors in Ewing sarcoma patients with lung metastases treated with busulfan and melphalan (BU-MEL) followed by whole-lung irradiation (WLI). Methods: This retrospective study included 68 lung metastatic Ewing Sarcoma patients who underwent WLI after BU-MEL with autologous stem cell transplantation, as part of two prospective and consecutive treatment protocols. WLI 12 Gy for <14 years old and 15 Gy for ≥14 years old patients were applied at least eight weeks after BU-MEL. Toxicity, overall survival (OS), event-free survival (EFS) and pulmonary relapse-free survival (PRFS) were estimated and analyzed. Results: After WLI, grade 1–2 and grade 3 clinical toxicity was reported in 16.2% and 5.9% patients, respectively. The five-year OS, EFS and PRFS with 95% confidence interval (CI) were 69.8% (57.1–79.3), 61.2% (48.4–71.7) and 70.5% (56.3–80.8), respectively. Patients with good histological necrosis of the primary tumor after neoadjuvant chemotherapy showed a significant decreased risk of pulmonary relapse or death compared to patients with poor histological necrosis. Conclusions: WLI at recommended doses and time interval after BU-MEL is feasible and might contribute to the disease control in Ewing sarcoma with lung metastases and responsive disease. Further studies are needed to explore the treatment stratification based on the histological response of the primary tumor.

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