Multisession gamma knife surgery for large brain metastases.

This study aimed to explore the safety and efficacy of multisession gamma knife surgery (GKS) for large brain metastases with a volume of 10 cm3 or larger. Fifty-six patients who had 65 brain metastases with a volume of at least 10 cm3 were treated with multisession GKS. Three-session GKS at a prescription dose of 10 Gy to the tumor margin per session with a 2-week interval between doses was performed in 3 patients. Other patients were treated with 2-session GKS at a prescription dose of 10-13 Gy to the tumor margin per session with an interval of 1-4 weeks. The median tumor volume was 21 cm3 . The median survival was 7 months. The 6-, 12-, and 18-month survival rates were 62, 42, and 31%, respectively. The progression-free survival rates at 6, 12, and 18 months were 93, 80, and 74%, respectively. At the time of the first and last GKS sessions, the median tumor volumes were 21 and 15 cm3 , respectively, which decreased to 5 cm3 with a median follow-up period of 6 months. Seventy-four percent of evaluated patients who had pre-GKS clinical symptoms obtained symptomatic improvement in a mean interval of 2 months. Multisession GKS was a safe and effective alternative to surgical resection for patients who had brain metastases with a tumor volume of 10 cm3 or larger. Although long-term results remain unclear, multisession GKS may be a suitable palliative treatment to preserve neurological function.