The role of Gamma Knife surgery in the treatment of skull base chordomas.

Skull base chordomas are a rare neoplasm arising from the notochord. Although histologically benign, these tumors are locally aggressive and present significant management challenges. The current series describes the experience at the University of Virginia with Gamma Knife surgery (GKS) in the treatment of chordomas. Fifteen patients (8 males and 7 females) had undergone GKS between 1990 and 2007. The median age was 46 years (range 13-80). The most common presenting symptom was visual disturbance, found in 73%. Twelve patients had undergone tumor resection. Mean tumor volume at the time of GKS was 5.8 cm3 (range 1.03-15.6 cm3). Mean prescription dose was 12.7 Gy (range 12-20) and mean maximal dose was 36.7 Gy (range 28-50). Imaging follow-up was available for all patients with a median time of 88 months (range 8-167 months), and clinical follow-up was available for 11 patients with a median of 70 months (range 8-132). Three patients underwent a second Gamma Knife surgery to treat out of field progression. A Kaplan-Meier plot showed 5 and 10 year actuarial tumor control rates of 50.3% including those undergoing repeat GKS. Symptomatic progression was seen in 75% of the patients. No statistically significant predictive variables among margin dose, maximal dose, tumor volume, number of isocenters, age, and gender were found. GKS affords a reasonable rate of local tumor control in patients with recurrent or residual chordomas. However further long-term follow-up would be necessary to exclude the possibility of late recurrences.