Local Control of Newly Diagnosed and Distally Recurrent, Low-Volume Brain Metastases With Fixed-Dose (20 Gy) Gamma Knife Radiosurgery

BACKGROUND: Metastases to the brain occur in 20% to 30% of patients with cancer and have been identified on autopsy in as many as 50% of patients. OBJECTIVE: To analyze the efficacy of 20-Gy Gamma Knife radiosurgery (GKR) as initial treatment in patients with 1 to 3 brain metastases <= 2 cm in greatest diameter. METHODS: A retrospective analysis of 114 consecutive adults with Karnofsky performance status >= 60 who received GKR for 1 to 3 brain metastases <= 2 cm in size was performed. Five patients lacked detailed follow-up and were excluded, leaving 109 for outcome analysis (34 men and 75 women; median age, 61.2 years). All metastases received 20 Gy to the 50% isodose line. RESULTS: One hundred nine patients underwent treatment of 164 metastases at initial GKR. Twenty-six patients (23.9%) were alive at last follow-up (median time, 29.9 months; range, 6.6 months to 7.8 years). The median overall survival was 13.8 months (range, 1 day to 7.6 years). Among the 52 patients with distant failure, 33 patients received 20 Gy to 95 new lesions. A total of 259 metastases received 20 Gy, and 4 patients lacked imaging follow-up secondary to death before posttreatment imaging. Local failure occurred in 17 of 255 treated lesions (6.7%), yielding an overall local control rate of 93.3%. Actuarial local control at 6, 12, 24, and 36 months was 96%, 93%, 89%, and 88%, respectively. Permanent neurological complications occurred in 3 patients (2.8%). CONCLUSION: Among patients with 1 to 3 brain metastases <= 2 cm in size who have not received whole-brain radiation therapy, GKR with 20 Gy provides high rates of local control with low morbidity and excellent neurological symptom-free survival.