International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationProton Radiotherapy for Pediatric Ewing's Sarcoma: Initial Clinical Outcomes
Introduction
Currently 60% to 70% of patients with localized Ewing’s sarcoma survive more than 5 years 1, 2, 3, 4. Because Ewing’s sarcoma is highly responsive to radiation therapy, and it often occurs in bones not easily resected, radiotherapy is a mainstay of treatment and is used in approximately 60% of Ewing’s sarcoma patients 5, 6, 7, 8, 9, 10, 11. Radiation is used in the postoperative setting for patients with close or positive resection margins and sometimes in the setting of a poor or slow clinical response to neoadjuvant chemotherapy 12, 13, 14, 15, 16. Radiation is typically used instead of surgery for children with unresectable tumors or in cases in which surgery would result in too great morbidity. However, definitive radiotherapy causes side effects as a result of the nontumor tissues irradiated in the process.
Proton radiotherapy (PT) can be prescribed similarly to photon radiotherapy to achieve comparable disease control rates at comparable doses. The chief advantage of protons in this setting is to spare acute and late toxicities by decreasing the amount of normal tissue receiving radiation. The absence of an exit dose beyond the Bragg peak results in approximately 50% to 60% reduction in integral dose (17). In this study, we report early clinical outcomes in children and adolescents with Ewing’s sarcoma who were treated with passively scattered three-dimensional (3D) conformal PT at Massachusetts General Hospital (Boston, MA).
Section snippets
Patients and procedures
A total of 30 children with Ewing’s sarcoma have been treated at the Francis H. Burr Proton Therapy Center at Massachusetts General Hospital between April 2003 and April 2009. All patients received chemotherapy based on the AEWS (A-Ewing Sarcoma) 0031 and POG (Pediatric Oncology Group) 9354 protocol followed by proton irradiation, with or without surgery. Computed tomography (CT) treatment planning was used in conjunction with additional diagnostic studies to assist in defining target volumes.
Results
All patients 21 years of age or younger with Ewing’s sarcoma who were treated at the Francis H. Burr Proton Therapy Center between April 2003 and April 2009 were included in this study. Patient and treatment characteristics are listed in Table 1. A total of 30 children (14 male and 16 female) received PT at a median age of 10 years (range, 1.8–21 years). The distribution of location of the tumors in this population was unusual compared with other published accounts, presumably because of the
Discussion
The clinical outcome of patients with Ewing’s sarcoma has improved considerably over the past several decades. This is largely due to multimodality therapy and improvements in systemic therapies as well as surgical and radiation therapy techniques. Current chemotherapeutic regimens using alkylating agents and topoisomerase II inhibitors have improved both local and distant control of disease (1). In addition, the use of diagnostic imaging including MRI, PET, and CT have permitted better
Conclusion
In summary, we provide evidence of good early clinical outcomes using PT for patients with Ewing’s sarcoma. Proton radiotherapy is well tolerated, with few acute affects and low rates of late side effects. The physical properties of protons reduce irradiation of healthy tissue without decreasing target coverage or compromising disease control. Although the follow-up is short, failures are typically seen within 2 years, and these early disease outcomes are comparable with those in the
Acknowledgments
We acknowledge Judith Adams, C.M.D., for her work on the figures.
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Supported in part by the Federal Share of program income earned by Massachusetts General Hospital on National Institutes of Health Grant #C06 CA059267, Proton Therapy Research and Treatment Center.
Conflict of interest: none.