Gamma knife radiosurgery for low-grade astrocytomas: results of long-term follow up.

OBJECT: The purpose of this paper is to report the long-term results of gamma knife radiosurgery (GKS) for low-grade astrocytomas.

METHODS: Fifty-one patients with low-grade astrocytomas treated with GKS and followed for more than 24 months are reported. Of the 51 patients, 12 harbored Grade I astrocytomas in and around the visual pathways and hypothalamus. The remaining 39 harbored Grade II astrocytomas. The mean patient age at time of GKS was 9.8 years for patient with Grade I and 30.9 years for those with Grade II astrocytomas. The mean tumor diameter was 25.4 mm for Grade I and 23.7 mm for Grade II tumors. The mean margin dose was 12.5 Gy for Grade I and 15.7 Gy for Grade II tumors. In the mean follow-up period of 27.6 months, both Grade I and Grade II astrocytomas responded well to GKS. Grade I astrocytomas had a response rate of 50% and a control rate of 91.7%. Grade II astrocytomas had a 46.2% response rate and an 87.2% control rate. Statistical analyses concerning the efficacy and related factors showed a significantly better response for patients 10 years of age or older with Grade I and those with a follow-up period of more than 24 months. Complications included radiation-induced edema in 18 (35.3%) of 51 cases, cyst formation or enlargement in five (9.8%), and transient tumor enlargement in three (5.9%).

CONCLUSIONS: Radiosurgery can play an important role in the treatment of low-grade astrocytomas, and complete cure of these tumors is expected in at least some of the cases.