Long-term results of Gamma Knife surgery for uveal melanomas

Gamma Knife surgery (GKS) is currently believed to be a safe and minimally invasive modality in the treatment of uveal melanomas. It could be used as an alternative treatment to enucleation, preserving the eyeball as well as visual function. The authors report their experiences with GKS for uveal melanomas for the period from February 1998 to December 2006.

Twenty-two patients with uveal melanoma were enrolled in this study. The population consisted of 12 men and 10 women with a mean age of 53.4 years (range 24-79 years). The mean tumor volume was 877 mm(3), and the mean margin dose was 45.6 Gy. The median follow-up period was 67 months (range 3-126 months). All of the patients had received a diagnosis and referral from an ophthalmology clinic; the patients underwent a preoperative orbital examination that included MRI.

Tumor regression was achieved in 20 patients (90.9%), whereas tumor progression was observed in 2 patients (9.1%) 3 years after GKS. The cumulative 1-year and 2-year mean rates of tumor thickness reduction were 18.8% and 42.8%, respectively. The mean rate of tumor volume reduction was 63.7%. The rate of eye retention 5 years after radiosurgery was 77.3% (17 of 22 patients). Overall visual acuity was reduced after GKS in all patients; 14 patients (63.6%) displayed preserved visual function better than hand-movement perception. The most frequent side effect was cataract, which was detected in 9 patients (40.9%); this was followed in frequency by radiation-induced retinopathy in 5 patients (22.7%).

Gamma Knife surgery provides excellent local control of uveal melanomas with a decrease in volume over time. This procedure not only preserves the eyeball and its potential visual function, but also decreases the potential for hematological dissemination and achieves sufficient local tumor control with a gradual reduction in volume.