Two-staged gamma knife radiosurgery for treatment of numerous (> 10) brain metastases

Objective: The treatment methodology as well as efficacy of stereotactic radiosurgery on numerous brain metastases has not been clearly established despite it being a primary modality for brain metastasis treatment. This study aimed to evaluate the efficacy of two-staged gamma knife radiosurgery (GKS) for patients with more than 10 metastatic lesions. Patients and Methods: Staged GKS was applied to 52 patients diagnosed with numerous metastases when a single radiosurgery was unbearable, or the exposed brain volume was excessive. Large clinically significant lesions in the eloquent area were treated in first GKS. The remainders were radiated in second GKS within a 4 week interval. The study evaluated three primary outcomes: 1) the radiological response at second GKS and 3 month follow up, 2) treatment-related side effects, and 3) survival after staged GKS treatment. Results: Irradiated lesions of 17 (32.7 %) patients showed radiological response on MRI at second GKS. Lesions non-treated at first GKS progressed in 13 (25.0 %) patients during the same period. At the 3-month follow-up, 5 (9.6 %) and 7 (13.5 %) patients were partially responsive and stable, respectively. Given that some patients expired from mostly non-neurological causes before the third follow-up, we could not detect an un-biased radiological progression. Nine (17.3 %) among 52 patients suffered grade 1-3 toxicity until the second GKS, whereas 4 (15.4 %) among 26 survivors suffered grade 1-2 CNS toxicity, but the relationship between irradiation and toxicity remained unclear. Survival rates for 52 patients at 3, 6, 12, 18 and 24 months were 63.9 %, 44.1 %, 23.3 %, 17.8 %, and 13.3 %, respectively. Longer survival after staged GKS treatment was observed in patients with KPS >= 80 rather than < 70, RPA II rather than III, and PIV < 7000 mm(3). However, the number of target lesions more or less than 10 was not correlated with survival. Conclusion: Although the clinical benefit as well as survival gain could not be clearly presented in this study, two-staged GKS for numerous metastases seems to benefit the patients' convenience and risk avoidance. Selected patients, especially with no other treatment options, can be candidates for this treatment protocol.