Retrospective Multicenter Study of Stereotactic Irradiation for Metastatic Brain Tumors in Japan

Abstract

Stereotactic Irradiation (STI) has been increasingly utilized in the management for metastatic brain tumor. However, many studies show combined therapy with surgery or whole brain radiation therapy (WBRT). The purpose of this study is to report the multicenter outcome of metastatic brain tumors treated only by STIs in Japan. This was a retrospective multicenter analysis to review a total of 686 patients with 918 lesions which had diameter > 10 mm. STIs were performed among 26 institutions participated in Japanese Radiation Oncology Study Group (JROSG) from January 2013 to December 2015 treated with linear accelerators. Previous WBRT or surgery cases were all excluded. Local control (LC), overall survival (OS), and brain necrosis followed with diagnostic MRI were analyzed by Kaplan-Meier method. Patient characteristics were as follows. Median age was 67 years (range: 26-91). Median follow-up was 12.1 months (range: 0.5-55.5), Median KPS score/ tumor size/ number of lesion were 90/ 17mm/ 2, respectively. Primary sites were lung/ breast/ GI/ others = 527/ 106/ 114/ 171 cases, respectively. Median dose delivered was 31.5 Gy in 3 fractions (range 13.4-55 Gy). Treatment outcome was CR/ PR/ SD/ PR = 151/ 349/ 167/ 145 and death/ survive = 510/ 280, respectively. 1-year LC was 80.5%. Median survival was 15.8 months. 1-year OS was 58.9%. 1-year LC for tumor size of 3-4 cm was 59.2%. There was no difference in LC between single fraction and multiple fractions. Brain necrosis occurred at 6 months/ 1-year = 4.8%/ 10.6%. The incidence was linearly correlated with the time after treatment. Positive outcome of STI for brain metastases without WBRT or surgery was achieved. LC was a little poor with the tumor diameter > 3 cm. Brain necrosis occurred regardless of a tumor size and a delivered dose, and long-term follow-up is mandatory.