Does debulking improve survival rate in advanced-stage retroperitoneal embryonal rhabdomyosarcoma?

Background, Methods, and Purpose: The authors examined demographic and clinical features, therapy, and outcome of patients with advanced (group III or IV) rhabdomyosarcoma (RMS) of the retroperitoneum and nongenitourinary pelvis treated in the Intergroup Rhabdomyosarcoma Study Group (IRSG) III (1984 to 1991, n = 41) or IV pilot (1987 to 1991, n = 53) studies to assess the role of initial debulking surgery. Results: Ninety-four patients with retroperitoneal primary tumors and gross locoregional residual tumor (group III, n = 53) or metastatic disease (group IV tumors, n = 41) were treated with combination chemotherapy (ie, vincristine, dactinomycin, and cyclophosphamide with or without other agents plus radiation therapy, RT) after biopsy only or subtotal resection. These retroperitoneal tumors usually were invasive (T2, 76%). Most patients were younger than 10 years of age (n = 69, 73%), the male to female ratio was 1.4, and tumors usually were embryonal (n = 64, 68%). Overall 4-year failure-free survival (FFS) was 50%; survival was 60%. Survival rate was better for girls (4-year survival rate, 75% v 49% for boys; P = .05) and was not significantly different for patients treated in IRS-III (66%) or IRS-IV pilot (52%). However, it was better for patients with embryonal versus alveolar or undifferentiated tumors (4-year survival rate, 70% v 42%; P = .002). In adolescents, RMS is different from that seen in children less than 10 years old; most cases are alveolar or undifferentiated (16 of 29, 55%). Surgery for most (21 of 24) patients with alveolar tumors comprised biopsy only. By contrast, of 64 patients with embryonal tumors, 39 (61%) underwent biopsy only, whereas 25 (39%) had debulking surgery. Patients whose tumors were debulked fared better than those whose tumors underwent biopsy only (4-year FFS rate, 72% v 48%; P = 0.03). Patients with group IV embryonal tumors fared unexpectedly better than those with group IV alveolar or undifferentiated tumors (70% versus 42% 4-year survival rate, P < .05), and patients less than 10 years of age with group IV embryonal tumors had 4-year survival rate of 77%, indicating the importance of the biology of these tumors. Conclusions: Multimodal therapy, including multiagent chemotherapy plus RT, appears to improve survival rate in patients with advanced embryonal RMS arising in the retroperitoneum. These data suggest that debulking tumors of embryonal histology improves outcome further. This approach will be assessed i