Preliminary results from a Phase II trail of conforml radiation therapy for pediatric patients with localised low-grade astrocytoma and ependymoma

Purpose: To estimate the local control and patterns of failure for pediatric patients with low-grade astroglial tumors (LGA) and ependymoma (EP) treated with three-dimensional conformal radiation therapy (CRT) using an anatomically defined clinical target volume (CTV). Methods and Materials: From an ongoing, prospective Phase II trial initiated in July 1997, 102 pediatric patients with LGA (n = 38) and EP (n = 64) have been treated with CRT using an anatomically defined CTV extending 1.0 cm beyond the gross tumor volume and a 0.5-cm margin (planning target volume) extending outside of the CTV. The prescribed dose was 54 Gy (LGA) and 59.4 Gy (EP). Results: Patients with EP have been followed for a median of 17 months (range 3-43 months), and six failures have occurred. Patients with LGA have been followed for a median of 17 months (3-44 months), and four failures have occurred. Three-dimensional magnetic resonance (MR) studies performed to document treatment failure were registered with the MR and computed tomography (CT) data used in the treatment planning process. Failure occurred within the CTV for 5 patients with EP, including 3 with concurrent subarachnoid dissemination. One patient with EP developed metastatic disease with no evidence of local failure. Three patients with LGA failed within the CTV and one failed immediately outside of the CTV. Conclusions: Treatment of an anatomically defined CTV, encompassing 1.0 cm of noninvolved brain beyond the margin of resection or neuroimaging-defined tumor, appears to be safe for pediatric patients with LGA and EP based on these preliminary data. Normal tissue sparing through the use of advanced radiation therapy treatment planning and delivery techniques should be beneficial to pediatric patients if the rate and patterns of failure are similar to conventional techniques and toxicity reduction can be objectively documented.