1508 / 1708
whose death was not attributed to disease progression or radiation
therapy) as competing risks. The longitudinal trends in neurocog-
nitive outcomes were estimated by using linear mixedmodels with
random coefficients.
23
SAS software was used for all analyses.
24
Data analyses were performed by the biostatistical coauthors.
RESULTS
Clinical and treatment characteristics of the study patients
are presented in Table 1. To identify similarities and differ-
ences among the patients, we categorized them according to
age (younger than 3 years or 3 years) for comparison.
Older patients were more likely to have supratentorial tu-
mors (
P
.012), and the younger patients were more likely
to have hydrocephalus (
P
.014) and require CSF shunting
(
P
.057). Larger proportions of the younger patients
received preirradiation chemotherapy and had anaplastic
tumors at diagnosis. However, these proportions were not
significantly different from those of the older patients.
Disease Control
The median length of follow-up was 38.2 months
(range, 12.4 to 75.6 months); 20 patients experienced dis-
ease progression, and the median time to progression for
those patients was 14 months (range, 6 to 26 months).
Failures were characterized as local (n 8), local distant
(n 4), and distant (n 8). There were no marginal
failures. The cumulative incidence of local failure estimate
at 3 years was 14.8% 4.0%. The actuarial PFS estimate at
3 years was 74.7% 5.7% (Fig 1). Thirteen of the failures
occurred among the 48 children younger than 3 years at the
time of irradiation. One patient died whose death was not
attributed to radiation therapy. He was censored at the time
of death when autopsy showed stable residual tumor. Uni-
variate analysis identified statistically significant differences
in actuarial 3-year event-free survival estimates based on
extent of resection (gross-total resection
v
near-total resec-
tion/subtotal resection; 77.6% 5.8%
v
42.9% 16.2%;
Table 1.
Demographic and Clinical Variables of Patients Categorized According to Age at Irradiation
Patient Characteristic
Age 3 Years
(n 40)
Age 3 Years
(n 48)
P
No. of
Patients
%
No. of
Patients
%
Length of follow-up, months
Median
34.7
25.6
Range
1.3-60.5
6.1-59.8
Sex
Female
19
47.5
22
45.8
.88
Male
21
52.5
26
54.2
CSF shunting
No
31
77.5
28
58
.057
Yes
9
22.5
20
42
Pre-CRT chemotherapy
No
35
87.5
37
77
.21
Yes
5
12.5
11
23
Extent of resection
Gross-total
34
85
40
83.3
.83
Near-total
2
5
4
8.3
Subtotal
4
10
4
8.3
Tumor grade
Anaplastic
13
32.5
22
45.8
.20
Differentiated
27
67.5
26
54.2
Tumor location
Infratentorial
26
65
42
87.5
.012
Supratentorial
14
35
6
12.5
No. of pre-CRT resections
1
26
65
30
63
.45
2
14
35
14
29
3
2
4
4
2
4
Hydrocephalus
No
16
46
8
17
.014
Yes
24
60
40
83
Abbreviation: CRT, conformal radiation therapy.
Merchant et al
3158
J
OURNAL OF
C
LINICAL
O
NCOLOGY