Results of gamma knife surgery alone for brain metastases. Indications for and limitations of local treatment protocol without prophylactic whole brain radiation therapy

The effectiveness of gamma knife surgery (GKS) for brain metastases without prophylactic whole brain radiation therapy (WBRT) was analyzed and indications for and limitations of the local treatment protocol are discussed herein. Among 1,474 cases with newly diagnosed brain metastases, 1,386 patients who satisfied the following 3 criteria were analyzed in this study, newly diagnosed brain metastases, tumor number and size within 10 Joules of total skull internal dose, no symptomatic carcinomatous meningitis. Large tumors were totally removed or irradiated by hypo-fractionated stereotactic radiotherapy using the gamma knife, while all small lesions were irradiated with GKS. Without upfront WBRT, new distant lesions identified on follow-up MRI every 2 to 3 months were appropriately re-treated with GKS. Overall, neurological, qualitative and new lesion-free survival curves were calculated and compared according to tumor number. In total, 2,355 separate GKS sessions were required to treat 13,319 lesions. The median overall survival period was 9.4 months. Neurological, qualitative, and new lesion-free survival rates at one year were 88.5%, 81.5% and 56.3%, respectively. The higher the tumor number, the poorer the prognosis for each type of survival. In meeting the goal of preventing neurological death and maintaining activities of daily living for patients with brain metastases who satisfy the 3 aforementioned inclusion criteria, GKS alone provides excellent palliation without prophylactic WBRT. Close observation and appropriate salvage treatment are essential. (author)