Effect of Radiotherapy Techniques (IMRT vs. 3D-CRT) on Outcome in Patients With Intermediate-Risk Rhabdomyosarcoma Enrolled in COG D9803—A Report From the Children’s Oncology Group

Abstract

Purpose To compare dosimetric parameters of intensity modulated radiation therapy (IMRT) and three-dimensional conformal radiation therapy (3DCRT) in patients with intermediate risk rhabdomyosarcoma (RMS), and to analyze their effect on local-regional control (LRC) and failure-free survival (FFS). Methods and Materials The study population consisted of 375 patients enrolled on Children’s Oncology Group protocol D9803, receiving IMRT or 3DCRT. Dosimetric data was collected from 179 patients with an available composite plan. Chi-square or Fisher’s exact tests were used to compare patient characteristics and radiotherapy (RT) parameters between the two groups. Time-to- event outcomes were estimated using the Kaplan-Meier method and compared using log-rank tests. Cox analysis was used to examine the effect of RT 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 3DCRT and IMRT respectively. No differences in 5 year failure of LRC (18% vs. 15%) and FFS (72% vs. 76%) were noted between the two groups. Multivariate analysis revealed no association between RT technique and FFS. Patients with primary tumors in parameningeal (PM) sites were more likely to receive IMRT than 3DCRT. IMRT became more common during the later years of the study. Patients receiving IMRT were more likely to receive >50Gy, photon energy of ≤6MV, and >5 RT fields than those who received 3DCRT. There was improved coverage of the IMRT planning target volume (PTV) by the prescription dose compared to the 3DCRT with similar target dose heterogeneity. Conclusions IMRT improved target dose coverage when compared to 3DCRT, though an improvement in LRC or FFS could not be demonstrated in this population. Future studies comparing integral dose to non-target tissue and late RT toxicity between the two groups is warranted.

Increased local failure for patients with intermediate‐risk rhabdomyosarcoma on ARST0531: A report from the Children's Oncology Group

“…[1][2][3] Because of the young patient age and extensive morbidity associated with salvage options after local relapse, [4][5][6][7] it is imperative to explore new strategies to improve local control. Prior strategies explored by the Intergroup Rhabdomyosarcoma Study Group and the Children's Oncology Group (COG), including radiation therapy (RT) dose escalation via a hyperfractionated approach and technical advances in imaging and RT, have not resulted in a difference in local control, although early data suggest that proton therapy may improve toxicity rates.…”

Radiation therapy target volume reduction in pediatric rhabdomyosarcoma

“…More recently, the development of advanced RT techniques, such as diagnostic image fusion for target delineation and intensity‐modulated radiation therapy (IMRT) with daily image guidance, have enabled the confident delivery of more conformal treatments with the possibility of reduced margins for treatment uncertainties. Several institutions have now reported promising clinical experience with IMRT for pediatric RMS 7‐10. The impetus for IMRT is to improve the conformality of the prescribed RT dose to the target volume, sparing more nontarget tissues from high‐dose radiation.…”

Ethical Analysis as a Tool for Addressing Treatment Controversies: Radiotherapy Timing in Children With Orbital Rhabdomyosarcoma as a Case Example

“…Nevertheless, the promise of IMRT should be viewed with caution, as long-term follow-up is required to determine if better target delineation translates into fewer radiation-induced sequelae [32]. Additionally, the use of IMRT and 3-D conformal therapy may carry an increased risk of second malignancy, compared with 2-D therapy, because IMRT and 3-D conformal therapy utilize a multifield, and sometimes multiplanar approach, translating to more normal tissue being exposed to a low dose of radiation [27,[33][34][35][36].…”