Background: There is at present no consensus on the policy for the treatmen
t of patients with low-grade gliomas (LGGs).
Methods: This report is a retrospective mufti-institutional study of 100 pa
tients (ages 16-65 years) with astrocytoma (grade II), oligodendroglioma, a
naplastic oligodendroglioma and anaplastic oligoastrocytoma of the supraten
torial areas which were treated with surgery and postoperative radiotherapy
at five university hospitals in northern Japan between 1990 and 1997 when
MRI was routinely used to determine the target volume. Most patients were i
rradiated with 50-60 Gy. The target volume usually covered the areas with T
2 prolongation of MRI with a margin of 2 cm.
Results: The disease-specific 5-year survival rate was 87.4% for patients w
ith oligodendroglioma and 75.3% for patients with astrocytoma. Survival for
patients with astrocytoma in the MRI era appears to be improved compared w
ith historical controls in the literature. Patients with astrocytoma aged 4
0 years and under had a significantly better disease-specific survival rate
than those over 40 years (P < 0.05) and patients with oligodendroglioma an
d oligoastrocytoma showed a similar tendency. Patients with astrocytoma who
had over 50% of their tumor removed had a significantly better survival ra
te than those who had less than 50% removed (P < 0.05). Chemotherapy appear
ed to improve the disease-specific survival rate of patients with oligodend
roglioma but not that of patients with astrocytoma.
Conclusion: Oligodendroglioma has a more protracted course of disease progr
ession than astrocytoma. This particular feature and the sensitivity of LGG
s to chemotherapy as well as their relevant prognostic factors, such as age
, histopathology and amount of tumor removal, should be taken into account
before any decision on treatment methods for LGGs is made.