Treatment planning and delivery of external beam radiotherapy for pediatric sarcoma: the St. Jude Children's Research Hospital experience.

PURPOSE: To describe and review the radiotherapy (RT) treatment planning and delivery techniques used for pediatric sarcoma patients at St. Jude Children's Research Hospital. The treatment characteristics serve as a baseline for future comparison with developing treatment modalities. PATIENTS AND METHODS: Since January 2003, we have prospectively treated pediatric and young-adult patients with soft-tissue and bone sarcomas on an institutional Phase II protocol evaluating local control and RT-related treatment effects from external-beam RT (conformal or intensity-modulated RT; 83.4%), low-dose-rate brachytherapy (8.3%), or both (8.3%). Here we describe the treatment dosimetry and delivery parameters of the initial 72 patients (median, 11.6 years; range, 1.4-21.6 years).
RESULTS: Cumulative doses from all RT modalities ranged from 41.4 to 70.2 Gy (median, 50.4 Gy). Median D(95) and V(95) of the planning target volume of external-beam RT plans were, respectively, 93.4% of the prescribed dose and 94.6% of the target volume for the primary phase and 97.8% and 99.2% for the cone-down/boost phase. The dose-volume histogram statistics for 27 critical organs varied greatly. The spinal cord in 13 of 36 patients received dose >45 Gy (up to 52 Gy in 1 cc) because of tumor proximity.
CONCLUSIONS: Planning and delivery of complex multifield external beam RT is feasible in pediatric patients with sarcomas. Improvements on conformity and dose gradients are still desired in many cases with sensitive adjacent critical structures. Long-term follow-up will determine the risk of local failure and the benefit of normal tissue avoidance for this population.