Purpose: To identify risk factors associated with out-comes in children with metastatic rhabdomyosarcoma (RMS) treated on the fourth Intergroup Rhabdomyosarcoma Study (IRS-IV).

Patients and Methods: Patients with metastatic RMS were treated with one of two regimens that incorporated a window of either ifosfamide and etoposide (IE) with vincristine, dactinomycin, and cyclophosphamide (VAC) or vincristine, melphalan (VM) and VAC. Study end points were failure-free survival (FFS) and overall survival (OS). Clinical factors including age, histology, sites of primary and metastatic disease, and number of sites of metastatic disease were correlated with those end points.

Results: One hundred twenty-seven patients were eligi-ble for analysis. The estimated 3-year OS and FFS for all patients were 39% and 25%, respectively. By univariate analysis, 3-year OS was significantly influenced by histology (47% for embryonal v 34% for all others, P. 026) and increasing number of metastatic sites (P. 028). By multivariate analysis, the presence of two or fewer metastatic sites was the only significant predictor (P. 007 and. 006, respectively). The combination of embryonal histology with two or fewer metastatic sites identified a subgroup with 3-year FFS of 40% and OS of 47%.

Conclusion: Children with group IV RMS treated on the