Ewing Tumor of Bone: Localized Tumors
Radiation therapy should be delivered in a setting in which stringent planning techniques are applied by those experienced in the treatment of ETB. Such an approach will result in local control of the tumor with acceptable morbidity in most patients.[1,2,19] The radiation dose may be adjusted depending on the extent of residual disease after the initial surgical procedure. Radiation therapy is generally administered in fractionated doses totaling approximately 55.8 Gy to the prechemotherapy tumor volume. A randomized study of 40 patients with ETB using 55.8 Gy to the prechemotherapy tumor extent with a 2 cm margin compared with the same total-tumor dose following 39.6 Gy to the entire bone showed no difference in local control or EFS. Hyperfractionated radiation therapy has not been associated with improved local control or decreased morbidity.
Higher rates of local failure are seen in patients older than 14 years who have tumors more than 8 cm in length. When radiation therapy was utilized for local control, the presence of metastatic disease at initial presentation was associated with higher risk for local failure. A retrospective analysis of patients with ETB of the chest wall compared patients who received hemithorax radiation therapy with those who received radiation therapy to the chest wall only. Patients with pleural invasion, pleural effusion, or intraoperative contamination were assigned to hemithorax radiation therapy. EFS was longer for patients who received hemithorax radiation, but the difference was not statistically significant. In addition, most patients with primary vertebral tumors did not receive hemithorax radiation and had a lower probability for EFS.
For patients with residual disease following attempt at surgical resection, the Intergroup Ewing Sarcoma Study (INT-0091 [POG-8850]) recommends 45 Gy to the original disease site plus a 10.8 Gy boost for patients with gross residual disease and 45 Gy plus a 5.4 Gy boost for patients with microscopic residual disease. No radiation therapy is recommended for those who have no evidence of microscopic residual disease following surgical resection.
Radiation therapy is associated with the development of second malignant neoplasms. A retrospective study noted that those patients who received 60 Gy or more had an incidence of second malignancy of 20%. Those who received 48 Gy to 60 Gy had an incidence of 5%, and those who received less than 48 Gy did not develop a second malignancy.
Treatment Options Under Clinical Evaluation
The following is an example of an international clinical trial that is currently being conducted. Information about ongoing clinical trials is available from the NCI Web site.
- COG-AEWS1031/RTOG 1127: This study is randomly assigning patients with newly diagnosed nonmetastatic ESFT to either standard interval-compressed VDC/IE or the experimental arm consisting of interval-compressed therapy with the addition of vincristine, cyclophosphamide, and topotecan (VTC [VTC/VDC/IE]). The primary objective is to evaluate the effect of a new treatment regimen on EFS and OS. Patients younger than 50 years are eligible. This study is available in North America through the COG and in the United States for medical and radiation oncologists through the Radiation Therapy Oncology Group or the Cancer Trials Support Unit.