Object: The combination approach of Ommaya reservoir placement and Gamma Knife surgery (GKS) was evaluated for the treatment of large cystic metastatic brain tumors.
Methods: The medical records of 22 patients harboring 28 tumors, who underwent Ommaya reservoir placement followed by GKS for large cystic metastatic brain tumors were retrospectively reviewed. The patients' ages ranged 26 to 77 years (mean 57.1 years). The most common locations of primary malignancy were the breast (11 patients) followed by the lung (seven patients). The mean maximum diameter of the tumor was 40.1 mm before Ommaya reservoir placement and 31.2 mm at GKS (mean reduction of 19.9%). The mean calculated tumor volume at GKS was 13.4 cm3. The mean tumor margin dose was 16 Gy in 17 patients treated by GKS only and 11 Gy in five patients treated using both GKS and external radiotherapy. The mean follow-up period was 11.5 months. Nineteen (67.9%) of the 28 tumors were controlled. The median patient survival time was 7 months. Asymptomatic intracystic hemorrhage associated with Ommaya reservoir placement was seen in two patients with four tumors, but no serious complication occurred.
Conclusions: Ommaya reservoir placement followed by GKS is relatively effective and safe for large cystic metastatic brain tumors. Gamma Knife surgery should be performed within a few days of Ommaya reservoir placement. Reaccumulation and high viscosity of cystic content must be considered.