Stereotactic Radiosurgery for Primary Central Nervous System Lymphoma: Results From the International Radiosurgery Research Foundation

BACKGROUND AND OBJECTIVES: Stereotactic radiosurgery (SRS) has been increasingly employed in the multimodal management of primary central nervous system lymphoma. Here, we evaluate the outcomes of SRS for the treatment of primary central nervous system lymphoma through a multicenter, international cohort study. METHODS: A multicenter, retrospective cohort study was conducted through the International Radiosurgery Research Foundation. Subgroups were defined according to treatment setting: up-front (primary treatment), boost (SRS after consolidative chemotherapy with or without whole-brain radiotherapy), and relapsed/refractory (recurrent/progressive disease after first-line therapy). The primary end point was local tumor control. Time-to-event analysis was conducted using the Kaplan-Meier method. Variables associated with local control were assessed using the Cox proportional hazard modeling. RESULTS: Fifty-four patients with 127 tumor sites were included in this analysis. Actuarial 12-month local and distant control rates for the entire cohort were 75.7% and 63.7%, respectively, with a median overall survival (OS) of 18 months (range: 1-176). Actuarial 12-month local control rates were significantly different at 95.6%, 78.3%, and 42.1% ( P < .0001) for the up-front, relapsed/refractory groups, and boost cohorts, respectively. OS across all cohorts were similar with 12-month OS rates of 55.2%, 51.3%, and 53.5% for the up-front, relapsed/refractory, and boost cohorts, respectively. Rates of radiation necrosis were 18.5%, 20.8%, 15.4%, and 11.8% for the entire cohort, relapsed/refractory, boost, and up-front cohorts, respectively. Diminished OS was significantly associated with treatment volumes >27 cm 3 (hazard ratio: 2.5, P = .04). CONCLUSION: SRS shows promising local tumor control rates for up-front and relapsed cohorts. Despite this, distant tumor progression limits total tumor control and may adversely affect OS.