Results from a phase II trial of conformal radiation therapy for pediatric patients with localized low-grade astrocytoma and quantification of radiation-related CNS effects

Abstract

8533 Background: A phase II trial of conformal radiation therapy (CRT) was conducted to determine if the irradiated volume could be reduced without affecting the rate of disease control for pediatric patients with localized low-grade astrocytoma (LGA) and to estimate the incidence and time to onset of clinically significant CNS effects. Methods: Between 8/97 and 1/03, 49 children (median age of 8.7 ± 4.0 yrs) were treated with CRT to 54 Gy using a 10mm anatomically-defined clinical target volume (CTV). The median CTV was 89.3 cc (range, 13.3–340.9 cc). Patients were evaluated serially with psychometric testing, provocative tests of endocrine function and standardized audiometry. Results: The study included mainly patients with juvenile pilocytic astrocytoma (n=31) involving the diencephalon or optic pathway (n=38) and the majority had visual impairment. Fourteen patients had prior chemotherapy and surgery was limited to subtotal resection (n=21) or biopsy (n=20). The 4-year actuarial event-free survival estimate was 84.2% ± 9.3% with a median follow-up of 31.0 months. Six patients experienced local (n=3) or distant (n=3) failure with a median time to failure of 18 months (range 5–54 months). A slight decline in scores for estimated IQ (−0.21 pts/yr; p=0.003), reading (−0.23 pts/yr, p=0.008), spelling (−0.19 pts/yr, p=0.02) and visual auditory learning (−0.16 pts/yr, p=0.06) were noted up to 48 months after CRT for the entire group. The effects on reading (p=0.044) and visual auditory learning (p=0.016) were more prominent in patients with large diencephalic and optic pathway tumors. Pre-CRT endocrinopathy was observed in the majority of patients affecting growth (43%), thyroid (34%), and ACTH (9%) secretion. Hearing loss due to CRT-alone was uncommon during the time interval of this study. Conclusions: The volume of irradiation may be reduced to a 10mm CTV without affecting disease control in localized LGA. Patients with LGA have a high rate of pre-existing endocrinopathy and the cognitive effects of treatment may be limited using focal radiation delivery strategies. No significant financial relationships to disclose.