Gamma Knife surgery targeting the resection cavity of brain metastasis that has progressed after whole-brain radiotherapy.

OBJECT: Salvage treatment of large, symptomatic brain metastases after failure of whole-brain radiotherapy (WBRT) remains challenging. When these lesions require resection, there are few options to lower expected rates of local recurrence at the resection cavity margin. The authors describe their experience in using Gamma Knife surgery (GKS) to target the resection cavity in patients whose tumors had progressed after WBRT. METHODS: The authors retrospectively identified 143 patients in whom GKS had been used to target a brain metastasis resection cavity between 2000 and 2005. Seventy-nine of these patients had undergone WBRT prior to resection and GKS. The median patient age was 53 years, and the median prescribed dose was 18 Gy (range 8-24 Gy), with resection cavities of relatively larger volume (> 15 cm3). The GKS dose was prescribed at the 40 to 95% isodose contour (mode 50%). Local recurrence within 1 cm of the treatment volume occurred in four (5.1%) of 79 cases. The median duration of time to local recurrence was 6.1 months (range 2-13 months). The median duration of time to occurrence of distant metastases following GKS of the resection cavity was 10.8 months (range 2-86 months). Carcinomatous meningitis developed in four (5.1%) of 79 cases. Symptomatic radionecrosis requiring surgical treatment occurred in three (3.8%) of 79 cases. The median duration of survival following GKS of the resection cavity was 69.6 weeks. The median 2- and 5-year survival rates were 20.2 and 6.3%, respectively. CONCLUSIONS: When metastases progress after WBRT and require resection, GKS targeting the resection cavity is a viable strategy. In 75 (94.9%) of 79 cases, GKS of the resection cavity in patients in whom WBRT had failed appears to have achieved its goal of local disease control.