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Clinical Investigation
Effect of Cerebellum Radiation Dosimetry on
Cognitive Outcomes in Children With
Infratentorial Ependymoma
Thomas E. Merchant, DO, PhD
, *Shelly Sharma, MD
, *Xiaoping Xiong, PhD,
y
Shengjie Wu, MS,
y
and Heather Conklin, PhD
z
*Division of Radiation Oncology and Departments of
y
Biostatistics and
z
Psychology, St. Jude
Children’s Research Hospital, Memphis, Tennessee
Received Dec 21, 2013, and in revised form Mar 28, 2014. Accepted for publication Jun 18, 2014.
Summary
This study associates longi-
tudinal deficits in intelli-
gence quotient (IQ) and
academic achievement with
collateral irradiation of the
posterior cerebellum in chil-
dren with infratentorial
ependymoma. To further
reduce cerebellum-linked
neurocognitive deficits, radi-
ation dose to the posterior
cerebellum should be avoi-
ded in treatment planning
and delivery. Advanced
methods of radiation therapy
may be used to further opti-
mize treatment of these
patients.
Purpose:
Cognitive decline is a recognized effect of radiation therapy (RT) in children
treated for brain tumors. The importance of the cerebellum and its contribution to
cognition have been recognized; however, the effect of RT on cerebellum-linked neu-
rocognitive deficits has yet to be explored.
Methods and Materials:
Seventy-six children (39 males) at a median 3.3 years of age
(range, 1-17 years old) were irradiated for infratentorial ependymoma from 1997 to
2008. The total prescribed dose was 54 to 59.4 Gy administered to the postoperative
tumor bed with 5- or 10-mm clinical target volume margin. Age-appropriate cognitive
and academic testing was performed prior to the start of RT and was then repeated at
6 months and annually throughout 5 years. The anterior and posterior cerebellum and
other normal brain volumes were contoured on postcontrast, T1-weighted postopera-
tive magnetic resonance images registered to treatment planning computed tomogra-
phy images. Mean doses were calculated and used with time after RT and other
clinical covariates to model their effect on neurocognitive test scores.
Results:
Considering only the statistically significant rates in longitudinal changes for
test scores and models that included mean dose, there was a correlation between mean
infratentorial dose and intelligence quotient (IQ; 0.190 patients/Gy/year;
P
Z
.001),
math ( 0.164 patients/Gy/year;
P
Z
.010), reading ( 0.137 patients/Gy/year;
P
Z
.011), and spelling scores ( 0.147 patients/Gy/year;
P
Z
.012), where Gy was
measured as the difference between the mean dose received by an individual patient
and the mean dose received by the patient group. There was a correlation between
mean anterior cerebellum dose and IQ scores ( 0.116 patients/Gy/year;
P
Z
.042)
and mean posterior cerebellum dose and IQ ( 0.150 patients/Gy/year;
P
Z
.002), math
Reprint requests to: Thomas E. Merchant, DO, PhD, Division of Ra-
diation Oncology, St. Jude Children’s Research Hospital, 262 Danny
Thomas Pl, Memphis, TN 38105-3678. Tel: (901) 595-3604; E-mail:
thomas.merchant@stjude.orgThis work was supported in part by National Cancer Institute Cancer
Center grant CA21765 and American Cancer Society research project
grant RPG-99-252-01-CCE and the American Lebanese Syrian and
Associated Charities.
Supplementary material for this article can be found at
www.redjournal.org.
Int J Radiation Oncol Biol Phys, Vol. 90, No. 3, pp. 547
e
553, 2014
0360-3016/$ - see front matter 2014 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.ijrobp.2014.06.043RadiationOncology
International Journal of
biology physics
www.redjournal.org