PURPOSE: To evaluate the outcome and toxicity of hyperfractionated radiotherapy (HFRT) vs. conventionally fractionated radiotherapy (CFRT) in children with Group III rhabdomyosarcoma (RMS).

METHODS AND MATERIALS: Five hundred fifty-nine children were enrolled into the Intergroup Rhabdomyosarcoma Study IV with Group III RMS. Sixty-nine were ineligible for the analysis because of incorrect group or pathologic findings. Of the 490 remaining, 239 were randomized to HFRT (59.4 Gy in 54 1.1-Gy twice daily fractions) and 251 to CFRT (50.4 Gy in 28 1.8-Gy daily fractions). The age range was or=5 years, 88% assigned to both HFRT and CFRT received their assigned treatment. The reasons for not receiving the appropriate randomized treatment were progressive disease, early death, parent or physician refusal, young age, or surgery. The toxicity assessment revealed more mucositis with HFRT (66%) than with CFRT (46%) (p = 0.03) for the parameningeal patients, and more skin reactions (16%) and nausea/vomiting (13%) with HFRT than with CFRT (7% and 5%, respectively) for patients with nonparameningeal primary tumors (p = 0.03 and p = 0.02, respectively). The analysis by treatment actually received revealed a 5-year FFS rate of 73% and OS rate of 77%, with no difference between CFRT and HFRT. As well, there was no difference in FFS or OS between CFRT and HFRT when analyzed by age, gender, tumor size, tumor invasiveness, modal status, histology, stage or site of primary. The 5-year estimated cumulative incidence of failure for the irradiated patients was local, 13%; regional, 3%; and distant, 13%; with no differences between HFRT and CFRT. The 5-year local failure rate by site was orbit, 5%; head and neck, 12%; parameningeal, 16%; bladder/prostate, 19%; extremity, 7%; and all others, 14%. The 5-year regional failure rate was parameningeal,1%; extremity, 20%; and all others, 5%. The 5-year distant failure rate was orbit, 2%; head and neck, 6%; parameningeal, 11%; bladder/prostate, 15%; extremity, 28%; and all others, 17%.

CONCLUSIONS: HFRT, as given in this study, did not improve local/regional control, FFS, or OS compared with CFRT. The risk of local/regional failure was comparable to that of distant failure in children with Group III RMS. The standard of care for Group III RMS continues to be CFRT with chemotherapy.