Application of intensity-modulated radiation therapy for pediatric malignancies

Novel radiation therapy delivery techniques have moved very slowly in the field of pediatric oncology. Some collaborative groups allow new radiation therapy delivery techniques in their trials. In many instances, the option of using these techniques is not addressed. These newer techniques of radiation delivery have the potential to reduce the probability of the common late effects of radiation and at the same time, potentially improve upon control and survival. The purpose of this study is to show the feasibility of IMRT in pediatric patients. No treatment results or toxicities will be presented. Five patients with a variety of pediatric malignancies received intensity-modulated radiation therapy (IMRT) at our institution as part of their disease management. A rigid immobilization device was developed for each patient and a computed tomography (CT) simulation was performed in the treatment position. In 3 of the patients, magnetic resonance imaging (MRI) scans were coregistered with the planning CT to facilitate target and critical structure delineation. In all but 1 patient, coplanar beam arrangements were used in the IMRT planning process. All IMRT plans exhibited a high degree of conformality. Dose homogeneity inside the tumor and rapid dose falloff outside the target volume is characteristic of IMRT plans, which allows for improved normal tissue sparing. Dose distributions were obtained for all plans, as well as dose and volume relationship histograms, to evaluate the fitness of the plans. IMRT is a viable alternative to conventional treatment techniques for pediatric cancer patients. The improved dose distributions coupled with the ease of delivery of the IMRT fields make this technique very attractive, especially in view of the potential to increase local control and possibly improve on survival.