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Prognostic factors for patients with
newly diagnosed low-grade oligodendroglial tumors: molecular genetics,
histopathology, and neuroimag
L. S. Ashby, J. K. Pueschel, A. C.
Scheck, S. W. Coons, W. R. Shapiro
Barrow Neurological Institute,
Phoenix, AZ
Background. Olidogdendroglial
tumors demonstrate both indolent and aggressive growth patterns.
Age, MRI enhancement, and proliferative
activity are potential predictors of outcome.
Deletion of 1p/19q chromosomal arms
correlates with survival and responsiveness to chemotherapy in
anaplastic tumors, but this relationship has not been established for
low-grade tumors.
Methods: Low-grade tumors were
identified from 210 oligodendroglial cases accrued through the end of
the year 2000.
We reviewed the histology and measured
proliferative activity by Ki67/MIB-1 immunohistochemistry.
Molecular analysis (FISH) identified
deletions of 1p and 19q.
Preoperative MRIs were reviewed for the
presence of enhancement.
Treatment and survival data were obtained
from clinical records.
Results: There were 139 cases:
95 oligodendrogliomas (O) and 44 oligoastrocytomas (OA).
The median ages were 39 and 34 years for O
and OA, respectively.
The median survival (MST) did not differ
between O (495 weeks) and OA (559 weeks).
Patients whose tumors had MIB-1 <5% had
MST of 495 weeks, compared to 220 weeks for those with MIB-1 >5%
(log rank p=0.0001).
There was a significant difference in MST
between patients with non-enhancing versus enhancing tumors: 447 weeks
and 343 weeks, respectively (log rank p<0.04).
Deletion of 1p correlated significantly
with survival (log rank p=0.0003).
No additional advantage was seen with
codeletion of 19q.
MST for patients whose tumors had no 1p
deletion was 361 weeks, but for those with 1p deletion MST has not yet
been reached.
Fifty-two patients (37%) received
treatment at the time of diagnosis: 31 had radiotherapy, 10 had
chemotherapy, and 11 had combination therapy.
Improved survival did not correlate with
treatment.
Conclusions: Individuals with
low-grade O and OA are expected to survive longer than those with
anaplastic variants.
Regardless of favorable low-grade
histology, high proliferative activity or the presence of enhancement
on MRI are associated with shortened survival.
1p deletion is a powerful prognostic
variable for patients with low-grade oligodendroglial tumors.
The contribution of treatment to extended
survival remains unclear.
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