Phase II trial of ifosfamide in children with malignant solid tumors.

Ifosfamide was given to 61 patients with malignant solid tumors diagnosed before the age of 21 years. In this phase II study, all patients received 1.6 g/m2/day X 5 iv over 15 minutes followed by mesna at a dose of 400 mg/m2 iv at 15 minutes and 4 and 6 hours after ifosfamide. Responses were observed in five of 15 patients with osteosarcoma, two of ten with neuroblastoma, two of six with Wilms' tumor, two of five with rhabdomyosarcoma, four of eight with other soft tissue sarcomas, one of one with retinoblastoma, one of two with germ cell tumors, one of one with B-cell lymphoma, and one of one with a primitive neuroectodermal tumor. Fifty-nine of 61 patients had received prior alkylating agent therapy which included cyclophosphamide, cisplatin, mechlorethamine, melphalan, or dacarbazine. Fourteen of 19 responses developed in patients whose tumors were resistant to treatment with cyclophosphamide. A patient with malignant Schwannoma who had received no prior chemotherapy developed a complete response which lasted 12 months. A patient with brain metastases of osteosarcoma has had complete response for greater than 2 years. Complete response was also observed in a patient with B-cell lymphoma. Toxicity consisted of mild to moderate nausea and vomiting, transient reversible myelosuppression, occasional elevation of serum BUN or creatinine, and transient neurotoxicity characterized by somnolence, confusion, weakness, tremor, hallucinations, or seizures. We conclude that ifosfamide is an important alkylating agent without apparent complete cross-resistance with cyclophosphamide, and as such should be further investigated for determination of its activity in patients with pediatric neoplasms and considered for incorporation into phase II-III trials for certain tumors.