Gamma Knife Radiosurgery for Metastatic Brain Tumors from Cancer of Unknown Primary

Objective We retrospectively analyzed treatment efficacy and identified prognostic factors impacting tumor control and survival in patients with brain metastases from cancer of unknown primary (CUP) treated with gamma knife radiosurgery (GKRS). Methods We retrospectively reviewed the medical records of 87 patients with 520 tumors who underwent GKRS for brain metastases from CUP. Results The median overall survival time after initial GKRS was 6 months. The 6- and 12-month overall survival rates were 79.3% and 14.9%, respectively. Older age ( P  = 0.002), lower Karnofsky Performance Status Index score ( P  = 0.026), extracranial metastases ( P  = 0.013), and multiple brain metastases ( P  = 0.007) were significantly correlated with shorter survival periods. The 6- and 12-month neurologic death rates were 25.3% and 32.2%, respectively. The 6- and 12-month neurologic deterioration rates were 24.1% and 27.6%, respectively. The 6- and 12-month distant brain control failure rates were 21.8% and 24.1%, respectively. The median tumor volume was 1.7 cm 3 . The median marginal prescription dose was 18 Gy. The 6- and 12-month tumor recurrence rates were 5.1% and 15.7%, respectively. Larger tumor volume ( P P  = 0.001) were significantly correlated with local tumor control failure. Seven patients had symptomatic radiation injury. The 6- and 12-month GKRS-related complication rates were both 6.9%. Conclusions Our findings suggest that GKRS is a relatively effective and safe treatment for control of tumor progression in patients with brain metastases from CUP. Overall and neurologic survivals were short, but we recommend GKRS treatment to prevent early neurologic dysfunction and death in patients with CUP.