Progress in the diagnosis and treatment of rhabdomyosarcoma and related soft tissue sarcomas

Advances in the diagnosis and treatment of rhabdomyosarcoma and related soft tissue sarcomas continue in the Intergroup Rhabdomyosarcoma Study Group (IRSG) and European cooperative groups. The use of molecular biology techniques in soft tissue sarcomas are redefining the classic pathology of these small blue cell tumors. Improvements in imaging, radiotherapy, and surgery, in part, deserve credit for the better survival seen in all cooperative trials. These advances confound the interpretation of consecutively run chemotherapy trials using historical comparisons. The IRSG has reported improvement in the prognosis of both nonmetastatic and metastatic embryonal rhabdomyosarcoma as attributable to three, three-drug regimens that use cyclophosphamide at 2.2 g/m2 in either maintenance or induction and maintenance therapy. Patients of any age with metastatic, nonembryonal, and those over 10 years of age with metastatic embryonal rhabdomyosarcoma continue to have a poor prognosis, which even megatherapy has failed to change. The doublet of ifosfamide and etoposide in combination with vincristine, actinomycin D, and cyclophosphamide at 2.2 g/m2 achieved a remarkable 3-year survival of 58% in patients with metastatic rhabdomyosarcoma and undifferentiated soft tissue sarcoma. The topoisomerase I inhibitor, topotecan, has recently been found by the IRSG to have a 57% overall response rate in patients with metastatic alveolar rhabdomyosarcoma. Topotecan has completed testing with cyclophosphamide in a phase II window study in newly diagnosed patients with metastatic disease and has been incorporated into a randomized trial in intermediate risk patients in IRSG-V. Molecular studies in IRSG-V will be applied in the detection of occult bone marrow metastases and the evaluation of resection margins at initial and second-look surgery. Long-term follow-up will be required in patients with gross residual sarcoma randomized to conventional and hyperfractionated radiotherapy in IRSG-IV to assess late effects. Although older patients with unfavorable histology and metastatic disease continue to have a poor prognosis, the overall 5-year survival of children and adolescents with nonmetastatic and metastatic rhabdomyosarcoma is approaching 80%. As molecular discoveries advance the diagnosis and detection of rhabdomyosarcoma, it is hoped that the futuristic molecular based treatment strategies in development and early testing will further improve survival in high-risk patients with metastatic soft tissue sarcoma.