Background: Brainstem metastases represent an uncommon clinical presentation that is associated with apoor prognosis. Treatment options are limited given the unacceptable risks associated withsurgical resection in this location. However, without local control, symptoms includingprogressive cranial nerve dysfunction are frequently observed. The objective of this studywas to determine the outcomes associated with linear accelerator-based stereotacticradiotherapy or radiosurgery (SRT/SRS) of brainstem metastases. Methods: We retrospectively reviewed 38 tumors in 36 patients treated with SRT/SRS betweenFebruary 2003 and December 2011. Treatment was delivered with the CyberknifeTM orTrilogyTM radiosurgical systems. The median age of patients was 62 (range: 28-89). Primarypathologies included 14 lung, 7 breast, 4 colon and 11 others. Sixteen patients (44%) hadreceived whole brain radiation therapy (WBRT) prior to SRT/SRS; ten had received priorSRT/SRS at a different site (28%). The median tumor volume was 0.94 cm3 (range: 0.01-4.2)with a median prescription dose of 17 Gy (range: 12-24) delivered in 1-5 fractions. Results: Median follow-up for the cohort was 3.2 months (range: 0.4-20.6). Nineteen patients (52%)had an MRI follow-up available for review. Of these, one patient experienced local failurecorresponding to an actuarial 6-month local control of 93%. Fifteen of the patients withavailable follow-up imaging (79%) experienced intracranial failure outside of the treatmentvolume. The median time to distant intracranial failure was 2.1 months. Six of the 15 patientswith distant intracranial failure (40%) had received previous WBRT. The actuarial overallsurvival rates at 6- and 12-months were 27% and 8%, respectively. Predictors of survivalincluded Graded Prognostic Assessment (GPA) score, greater number of treatment fractions,and higher prescription dose. Three patients experienced acute treatment-related toxicityconsisting of nausea (n = 1) and headaches (n = 2) that resolved with a short-course ofdexamethasone. Conclusion: SRT/SRS for brainstem metastases is safe and achieves a high rate of local control. We foundhigher GPA as well as greater number of treatment fractions and higher prescription dose tobe correlated with improved overall survival. Despite this approach, prognosis remains poorand distant intracranial control remains an issue, even in patients previously treated withWBRT.
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