Gamma Knife surgery for primary central nervous system lymphoma: usefulness as palliative local tumor control.

OBJECT: Although there is no established treatment for primary central nervous system lymphoma (PCNSL), therapeutic protocols involving high-dose methotrexate therapy followed, in some cases, by whole-brain radiotherapy (WBRT) have generally been adopted, and they have yielded relatively favorable results. Gamma Knife surgery (GKS) is a stopgap measure to treat patients with PCNSL. The authors summarize the results of their cases and evaluate the efficacy and usefulness of GKS. METHODS: Between June 1999, and June 2005, 22 patients suffering from PCNSL were treated with GKS at the authors' institution and were followed up for more than 6 months. Some combination of chemotherapy and/or WBRT and/or microsurgery had been performed in 18 of the 22 patients before GKS. The remaining four patients had not undergone any previous treatment. In these patients, the mean tumor volume was 4.14 cm3, and the tumors were treated with a mean margin dose of 16.5 Gy to the 52.8% isodose line. Magnetic resonance imaging demonstrated the disappearance of the GKS-treated lesions; however, new lesions were observed in other regions of the brain in 10 patients and repeated GKS was performed in some cases. No local recurrences were observed an average of 19.4 months after GKS, and good level of quality of life (QOL) was maintained during this period. CONCLUSIONS: Gamma Knife surgery should be performed only for local tumor control as a stopgap measure in the treatment of PCNSL. It is noninvasive and safe, and its effects occur rapidly. Its use improves prognosis and enhances the patient's quality of life. Gamma Knife surgery should be considered one of the treatment strategies for patients with PCNSLs.