PURPOSE: To compare the dosimetric parameters of intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) in patients with intermediate-risk rhabdomyosarcoma and to analyze their effect on locoregional control and failure-free survival (FFS). METHODS AND MATERIALS: The study population consisted of 375 patients enrolled in the Children's Oncology Group protocol D9803 study, receiving IMRT or 3D-CRT. Dosimetric data were collected from 179 patients with an available composite plan. The chi-square test or Fisher's exact test was used to compare the patient characteristics and radiotherapy parameters between the two groups. The interval-to-event outcomes were estimated using the Kaplan-Meier method and compared using log-rank tests. Cox proportional hazards regression analysis was used to examine the effect of the treatment technique on FFS after adjusting for primary site and risk group. RESULTS: The median follow-up time was 5.7 and 4.2 years for patients receiving 3D-CRT and IMRT, respectively. No differences in the 5-year failure of locoregional control (18% vs. 15%) or FFS (72% vs. 76%) rates were noted between the two groups. Multivariate analysis revealed no association between the two techniques and FFS. Patients with primary tumors in parameningeal sites were more likely to receive IMRT than 3D-CRT. IMRT became more common during the later years of the study. Patients receiving IMRT were more likely to receive >50 Gy, photon energy of 5 radiation fields than those who received 3D-CRT. The coverage of the IMRT planning target volume by the prescription dose was improved compared with the coverage using 3D-CRT with similar target dose heterogeneity. CONCLUSIONS: IMRT improved the target dose coverage compared with 3D-CRT, although an improvement in locoregional control or FFS could not be demonstrated in this population. Future studies comparing the integral dose to nontarget tissue and late radiation toxicity between the two groups are warranted.

PURPOSE: To analyze the effect of reduced-dose radiotherapy on local control in children with low-risk rhabdomyosarcoma (RMS) treated in the Children's Oncology Group D9602 study. METHODS AND MATERIALS: Patients with low-risk RMS were nonrandomly assigned to receive radiotherapy doses dependent on the completeness of surgical resection of the primary tumor (clinical group) and the presence of involved regional lymph nodes. After resection, most patients with microscopic residual and uninvolved nodes received 36 Gy, those with involved nodes received 41.4 to 50.4 Gy, and those with orbital primary tumors received 45 Gy. All patients received vincristine and dactinomycin, with cyclophosphamide added for patient subsets with a higher risk of relapse in Intergroup Rhabdomyosarcoma Study Group III and IV studies. RESULTS: Three hundred forty-two patients were eligible for analysis; 172 received radiotherapy as part of their treatment. The cumulative incidence of local/regional failure was 15% in patients with microscopic involved margins when cyclophosphamide was not part of the treatment regimen and 0% when cyclophosphamide was included. The cumulative incidence of local/regional failure was 14% in patients with orbital tumors. Protocol-specified omission of radiotherapy in girls with Group IIA vaginal tumors (n = 5) resulted in three failures for this group. CONCLUSIONS: In comparison with Intergroup Rhabdomyosarcoma Study Group III and IV results, reduced-dose radiotherapy does not compromise local control for patients with microscopic tumor after surgical resection or with orbital primary tumors when cyclophosphamide is added to the treatment program. Girls with unresected nonbladder genitourinary tumors require radiotherapy for postsurgical residual tumor for optimal local control to be achieved.

PURPOSE: Radiation therapy remains an essential treatment for patients with parameningeal rhabdomyosarcoma (PMRMS), and early radiation therapy may improve local control for patients with intracranial extension (ICE). METHODS AND MATERIALS: To address the role of radiation therapy timing in PMRMS in the current era, we reviewed the outcome from 2 recent clinical trials for intermediate-risk RMS: Intergroup Rhabdomyosarcoma Study (IRS)-IV and Children's Oncology Group (COG) D9803. The PMRMS patients on IRS-IV with any high-risk features (cranial nerve palsy [CNP], cranial base bony erosion [CBBE], or ICE) were treated immediately at day 0, and PMRMS patients without any of these 3 features received week 6-9 radiation therapy. The D9803 PMRMS patients with ICE received day 0 X-Ray Therapy (XRT) as well; however, those with either CNP or CBBE had XRT at week 12. RESULTS: Compared with the 198 PMRMS patients from IRS-IV, the 192 PMRMS patients from D9803 had no difference (P < .05) in 5-year local failure (19% vs 19%), failure-free-survival (70% vs 67%), or overall survival (75% vs 73%) in aggregate. The 5-year local failure rates by subset did not differ when patients were classified as having no risk features (None, 15% vs 19%, P = .25), cranial nerve palsy/cranial base of skull erosion (CNP/CBBE, 15% vs 28%, P = .22), or intracranial extension (ICE, 21% vs 15%, P = .27). The D9083 patients were more likely to have received initial staging by magnetic resonance imaging (71% vs 53%). CONCLUSIONS: These data support that a delay in radiation therapy for high-risk PMRMS features of CNP/CBBE does not compromise clinical outcomes.