Treatment of Children with Peripheral Primitive Neuroectodermal Tumor or Extraosseous Ewingʼs Tumor with Ewingʼs-Directed Therapy

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Abstract
We report the treatment and outcome of patients with peripheral primitive neuroectodermal tumor (PNET) and extraosseous Ewing's tumor (EOE) using Ewing's-directed therapy, including an ifosfamide and etoposide window. Seventeen pediatric patients with peripheral PNET (n = 14) or EOE (n = 3) were enrolled between 1988 and 1992 on our institutional Ewing's protocol. Induction therapy comprised a 9-week "window" of ifosfamide and etoposide, followed by 9 weeks of therapy with cyclophosphamide and Adriamycin (Adria Laboratories, Columbus, OH). Response assessment after 17 weeks was followed by surgery and/or radiotherapy (doses based on tumor size and response to induction), repeat evaluation, and maintenance chemotherapy with alternating courses of vincristine/dactinomycin, ifosfamide/etoposide, and cyclophosphamide/Adriamycin for a total of 45 weeks. At diagnosis, 8 patients had large lesions (>8 cm) and 3 had pulmonary metastases (1 with large tumor). Surgical resection was performed at diagnosis for 9 patients and after induction therapy for 5. During window therapy, all of the 9 evaluable patients responded (8 partial, I objective), and no patient without measurable disease developed disease progression. Responses were maintained or improved during subsequent induction in six of the patients with residual disease. Fourteen patients received local radiotherapy. At 49 to 94 months after diagnosis, 12 patients are disease-free (1 in second remission), 4 have died, and 1 is alive with disease. The five-year overall and progression-free survival rates are 77 +/- 13% and 62 +/- 16%, respectively. The use of consistent Ewing's-directed combined-modality therapy for patients with soft tissue peripheral PNET/EOE results in survival similar to that of patients with osseous Ewing's tumor. The combination of ifosfamide and etoposide appears active and should be incorporated in future treatment protocols.