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METHODS AND MATERIALS
Study group
Between 1963 and 1994, 80 patients with ependymomas
were identified from the Radiation Oncology Tumor Reg-
istry. The outcome of therapy was retrospectively analyzed.
Included in the study were 33 females and 47 males ranging
in age from 1 to 69 years, with a median age of 33.5 years.
Statistical methods
Survival and local control rates were the principle end-
points of the analysis. Local failure was defined as progres-
sion of local symptoms or as tumor growth documented on
neuroimaging studies. Survival and local control rates were
determined with the Kaplan-Meier product limit method.
The statistical significance of differences between the
curves was determined by the log-rank test. Multivariate
analysis was performed with the Cox proportional hazards
model. Follow-up ranged from 5 to 30 years, with a median
follow-up of 10.4 years.
Surgery and pathologic features
Primary sites included the supratentorial brain in 13 pa-
tients, infratentorial brain in 32 patients, and spinal cord in
35 patients. Seventy patients were found to have low-grade
(1 and 2) tumors and 10 had high-grade (3 and 4) tumors.
The distribution of tumor grade, sub-type, and site of origin
are found in Tables 1 and 2. Myxopapillary tumors were
uniformally grade 1 tumors found in the lumbar spine
region. The following studies were performed to assess for
seeding of the central nervous system (CNS): myelography
in 40 patients, MRI in 21 patients, CT scans in 25 patients,
and CSF cytology in 24 patients. Based on the findings of
clinical studies (myelography, MRI, CT, or CSF cytology),
4 patients (6%) were found to have seeding of the CNS at
the time of diagnosis, including 2 of 70 (3%) with low-grade
tumors and 2 of 10 (20%) with high-grade tumors.
The extent of tumor resection was determined by a care-
ful review of operative reports. Gross total resections were
performed in 17 (21%) patients, subtotal resections in 57
(71%) patients, and biopsy alone in the remaining 6 (8%)
patients (Table 3). Of the 45 patients with tumors arising in
the brain, gross total resections were performed in 7 (16%),
subtotal resections in 36 (80%), and biopsies in 2 (4%). Of
the 35 patients with tumors arising in the brain, gross total
resections were performed in 10 (29%), subtotal resections
in 21 (67%), and biopsies in 4 (11%).
Tumors were graded on a 4 grade scale: grade 1 lesions
lacked mitotic activity; grade 2 lesions exhibited occasional
mitoses; grade 3 lesions showed brisk mitotic activity, and
often some endothelial proliferation; grade 4 tumors showed
high mitotic indices and prominent endothelial prolifera-
tion. As a rule, high-grade (3 and 4) were markedly cellular
and often showed nucleolar prominence. Palisading necro-
sis was most often seen in grade 4 lesions. Cellular pleo-
morphism and simple non-palisading necrosis were not
considered useful grading parameters.
Post-operative therapy
All 80 patients underwent radiation therapy as a portion
of their initial treatment sequence (Table 3). The most
common indication for radiotherapy was the presence of
residual tumor in 63 patients. The remaining 17 patients
received adjuvant therapy following gross total resection,
78 of whom received treatment at Mayo Clinic and 2 at
other institutions. Treatment was delivered with 4, 6, or 10
MV photons. Radiotherapy was delivered to the craniospi-
nal axis in 20 patients, to the whole brain in 3 patients, to the
total spine in 6 patients, and to the primary tumor bed (brain
or spine) alone in the remaining 51 cases. Doses adminis-
tered to the primary tumor bed and to areas of gross disease
ranged from 24 to 59.4 Gy (median 49.7 Gy) in 1.8–2.0 Gy
fractions. Twenty-five (31%) of the 80 patients received
doses less than 45 Gy to the primary tumor bed. Prophy-
lactic doses administered to uninvolved regions ranged from
28.5 to 40.0 Gy. The doses delivered and the field arrange-
ments used were based on the treating physician’s prefer-
ences.
Table 2. Tumor type and site of origin
Tumor type Brain Upper spine Lumbar spine Total
Myxopapillary
0
0
12
12
Other types
45
16
7
68
Total
45
16
19
80
Table 1. Tumor grade and site of origin
Tumor grade
Brain
Spine
Total
1–2
36
34
70
3–4
9
1
10
Total
45
35
80
Table 3. Summary of therapy
Tumor grade
Surgery
Radiotherapy
Biopsy
STR GTR Local field
WBRT/WSRT
CSRT
Adjuvant chemotherapy
1–2
6
49
15
49
8
13
1
3–4
0
8
2
2
1
7
0
STR
5
subtotal resection; GTR
5
gross total resection; WBRT
5
whole brain radiotherapy; WSRT
5
whole spine radiotherapy;
CSRT
5
craniospinal radiotherapy.
954
I. J. Radiation Oncology
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Biology
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Physics
Volume 42, Number 5, 1998