Stereotactically guided conformal radiotherapy for progressive low-grade gliomas of childhood.
OBJECTIVE
To describe the rationale, technique, and early results of stereotactically guided conformal radiotherapy (SCRT) in the treatment of progressive or inoperable low-grade gliomas (LGGs) of childhood.


METHODS
Between September 1994 and May 1999, 14 children (median age 6 years, range 5-16) with LGG were treated with SCRT at the Royal Marsden NHS Trust. Tumors were located at the optic chiasm (n = 9), third ventricle (n = 2), hypothalamus, craniocervical junction, and pineal region (each n = 1). Four patients received chemotherapy before SCRT. Immobilization was in a Gill-Thomas-Cosman frame (n = 12) and subsequently in a specially designed pediatric version of the frame (n = 2). Stereotactic coordinates and the tumor were defined by CT scanning with a fiducial system and MRI fusion. The median tumor volume was 19.5 cm(3) (range 7.5-180). The planning target volume was defined as the area of enhancing tumor plus a 5-10-mm margin. The treatment technique consisted of 4 isocentric, noncoplanar, conformal, fixed fields. Treatment was delivered in 30-33 daily fractions to a total dose of 50-55 Gy.


RESULTS
SCRT was well tolerated, with transient hair loss the only acute toxicity. The median follow-up was 33 months (range 2-53). At 6 months after SCRT, 4 of 12 children with neurologic deficits improved and 5 remained stable. Twelve children were available for MRI evaluation. Two had a complete response, 6 a partial response, and 4 stable disease. One child with optic chiasm glioma had local progression at 25 months, and 1 developed diffuse leptomeningeal disease without local progression at 27 months. The 3-year local progression-free survival and overall survival rate after SCRT was 87% and 100%, respectively, compared with 89% and 98% for an historic control treated with conventional RT. New endocrine deficiencies were noted in 2 children after a follow-up of 20 and 23 months.


CONCLUSIONS
SCRT is a feasible, high-precision technique of RT for children with LGGs for whom RT is considered appropriate. The local control and acute toxicity of SCRT are comparable to a historic control of patients with conventionally delivered RT. The frequency of delayed hypothalamic-pituitary axis dysfunction reflects tumor location adjacent to the hypothalamus and pituitary. Additional follow-up is required to demonstrate that SCRT contributes to a reduction in treatment-related late toxicity, while maintaining the local control achieved with conventionally delivered RT in children with progressive LGGs.
Saran
Frank H
FH
Neuro-oncology Unit and Academic Unit of Radiotherapy and Oncology, Institute of Cancer Research and Royal Marsden NHS Trust, Sutton, Surrey SM2 5PT, UK. Frank.Saran@rmh.nthames.nhs.uk
Baumert
Brigitta G
BG
Khoo
Vincent S
VS
Adams
Elizabeth J
EJ
Garré
Maria L
ML
Warrington
Alan P
AP
Brada
Michael
M
D000293:Adolescent; D001254:Astrocytoma / Q000473:pathology / Q000532:radiotherapy*; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000379:methods*; D013238:Stereotaxic Techniques / Q000295:instrumentation