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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
T. E. Merchant, E. N. Kiehna, R. K. Mulhern, L. E. Kun, S. Wu, X. Xiong, T.
Williams, A. Gajjar, F. A. Boop, R. A. Sanford
St. Jude Children's Research Hospital, Memphis, TN
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.
Copyright 2004 American Society of Clinical Oncology All rights
reserved worldwide.
Source: http://www.asco.org/ac/1,1003,_12-002636-00_18-0026-00_19-004003,00.asp
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