Supratentorial low-grade glioma in adults: an analysis of prognostic factors and timing of radiation.

PURPOSE: To review the outcomes of patients with low-grade glioma diagnosed by modern imaging and treated at a center where postponing radiotherapy was common practice.
METHODS: We reviewed the records of patients (age > or = 18 years) with pathologically confirmed supratentorial low-grade fibrillary astrocytoma, oligodendroglioma, and mixed glioma treated at a regional cancer center in Canada between 1979 and 1995.
RESULTS: Median survival for the entire group (N = 167; mean age 40.6 years) was 10.5 years with 5- and 10-year survival rates of 72% and 50%, respectively. Median progression-free survival was 4.9 years with 5- and 10-year progression-free rates of 50% and 12%, respectively. Overall and progression-free survivals were longer for patients with an oligodendroglioma or mixed glioma than with astrocytoma (median 13 v 7.5 years, P = .003; progression-free 5.6 v 4.4 years, p = .054). Age at diagnosis < or = 40 years, seizures at presentation, minimal residual tumor after surgery, Karnofsky performance status > or = 70, and oligodendroglioma or mixed glioma pathology were associated with significantly longer median survival on univariate and multivariate analyses. Radiotherapy deferred until tumor progression (v immediate radiotherapy) was associated with longer survival on univariate analysis, but an imbalance in other variables accounted for this advantage such that timing of radiotherapy was not an independent (favorable or adverse) prognostic factor on multivariate analysis.
CONCLUSION: Patients with low-grade glioma diagnosed by modern imaging can be expected to live a long time; timing of radiotherapy may be a less important determinant of survival than nontreatment variables and residual tumor bulk.