BACKGROUND: We reviewed 56 IRS-IV patients with localized rhabdomyosarcoma [RMS] of the retroperitoneum/pelvis to assess outcome and prognostic factors, including the value of initially excising >or=50% of the tumor (debulking) before chemotherapy. METHODS: Patients had embryonal RMS [N=38], alveolar RMS [N = 7], RMS not otherwise specified [NOS, N = 7], or undifferentiated sarcoma [N = 4]. Fifteen patients were debulked; 41 patients were biopsied. All received VAC; most received radiotherapy. RESULTS: Estimated 5-year failure-free survival [FFS] and overall survival rates were 70 and 75%, respectively. FFS rates were better for patients <10 years old and those with embryonal RMS compared to alveolar RMS/undifferentiated sarcoma. After adjusting for age and histological differences, FFS was better for patients whose tumor was debulked prior to beginning therapy [P = 0.02]. CONCLUSIONS: These results are superior to those of previous protocols for patients with RMS of the retroperitoneum/pelvis. Initial excision of >or=50% of the tumor may be associated with increased FFS. Copyright 2004 Wiley-Liss, Inc.