Ewing Sarcoma: Localized Tumors
Standard Treatment Options
Because most patients with apparently localized disease at diagnosis have occult metastatic disease, multidrug chemotherapy as well as local disease control with surgery and/or radiation is indicated in the treatment of all patients.[1-8] Current regimens for the treatment of localized Ewing sarcoma achieve event-free survival (EFS) and overall survival (OS) of approximately 70% at 5 years after diagnosis.
Current standard chemotherapy in the United States includes vincristine, doxorubicin, and cyclophosphamide, also known as VAdriaC or VDC, alternating with ifosfamide and etoposide (IE). The combination of IE has shown activity in Ewing sarcoma, and a large randomized clinical trial and a nonrandomized trial demonstrated that outcome was improved when IE was alternated with VAdriaC.[2,9,10] Dactinomycin is no longer used in the United States but continues to be used in the Euro-Ewing studies. Increased dose intensity of doxorubicin during the initial months of therapy was associated with an improved outcome in a meta-analysis done prior to the standard use of ifosfamide and etoposide. The use of high-dose VAdriaC has shown promising results in small numbers of patients. A single institution study of 44 patients treated with high-dose VAdriaC and IE had an 82% 4-year EFS. However, in an intergroup trial of the Pediatric Oncology Group and the Children's Cancer Group, which compared a dose-intensified chemotherapy regimen of vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide (VDC/IE) with standard doses of the same regimen, no differences in outcome were observed. Unlike the single institution trial, this trial did not maintain the dose intensity of alkylating agents for the duration of treatment.
In a completed Children's Oncology Group (COG) trial (COG-AEWS0031), 568 patients with newly diagnosed localized extradural Ewing sarcoma were randomly assigned to receive chemotherapy (VAdriaC alternating with IE) given every 2 weeks (interval compression) versus every 3 weeks (standard). Patients randomly assigned to the every 2-week interval of treatment had an improved 5-year EFS (73% vs. 65%, P = .048). There was no increase in toxicity observed with the every 2-week schedule.
Local control can be achieved by surgery and/or radiation. Surgery is generally the preferred approach if the lesion is resectable.[15,16] The superiority of resection for local control has never been tested in a prospective randomized trial. The apparent superiority may represent selection bias. In past studies, smaller more peripheral tumors were more likely to be treated by surgery, and larger, more central tumors were more likely to be treated by radiation therapy. An Italian retrospective study showed that surgery improved outcome only in extremity tumors, although the number of patients with central axis Ewing sarcoma who achieve adequate margins is small. In a series of 39 patients treated at St. Jude Children's Research Hospital, who received both surgery and radiation, the 8-year local failure rate was 5% for patients with negative surgical margins and 17% for those with positive margins. Data for patients with pelvic primary Ewing sarcoma from a North American intergroup trial showed no difference in local control or survival based on local-control modality—surgery alone, radiation therapy alone, or radiation plus surgery.
If a very young child has Ewing sarcoma, surgery may be a less morbid therapy than radiation therapy because of the retardation of bone growth caused by radiation. Another potential benefit for surgical resection of the primary tumor is information concerning the amount of necrosis in the resected tumor. Patients with residual viable tumor in the resected specimen have a worse outcome than those with complete necrosis. In a French Ewing study (EW88), EFS for patients with less than 5% viable tumor, 5% to 30% viable tumor, and more than 30% viable tumor was 75%, 48%, and 20%, respectively. European investigators are studying whether treatment intensification (i.e., high-dose chemotherapy with stem cell rescue) will improve outcome for patients with a poor histologic response. Radiation therapy should be employed for patients who do not have a surgical option that preserves function and should be used for patients whose tumors have been excised but with inadequate margins. Pathologic fracture at the time of diagnosis does not preclude surgical resection and is not associated with adverse outcome.
Radiation therapy should be delivered in a setting in which stringent planning techniques are applied by those experienced in the treatment of Ewing sarcoma. Such an approach will result in local control of the tumor with acceptable morbidity in most patients.[1,2,20] 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 Ewing sarcoma 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.
Comparison of proton-beam radiation therapy and intensity-modulated radiation therapy (IMRT) treatment plans has shown that proton-beam radiation therapy can spare more normal tissue adjacent to Ewing sarcoma primary tumors than IMRT. Follow-up remains relatively short, and there are no data available to determine if the reduction in dose to adjacent tissue will result in improved functional outcome or reduce the risk of secondary malignancy. Because patient numbers are small and follow-up is relatively short, it is not possible to determine if the risk of local recurrence might be increased by reducing radiation dose in tissue adjacent to the primary tumor.
Higher rates of local failure are seen in patients older than 14 years who have tumors more than 8 cm in length. A retrospective analysis of patients with Ewing sarcoma 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 is 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) 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 (Combination Chemotherapy in Treating Patients With Nonmetastatic Extracranial Ewing Sarcoma): This study is randomly assigning patients with newly diagnosed nonmetastatic Ewing sarcoma 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.
Check for U.S. clinical trials from NCI's list of cancer clinical trials that are now accepting patients with localized Ewing sarcoma/peripheral primitive neuroectodermal tumor. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.
General information about clinical trials is also available from the NCI Web site.References
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