The more the merrier.
The Study: To avoid the time and expense of a clinical trial, eight “high-volume” academic institutions (read: radiosurgery junkies) joined together to report their outcomes treating as many as 15 brain mets in a single treatment. In this multi-institutional analysis, over 200 patients receiving radiosurgery for 5-15 brain mets were compared to nearly 1000 patients treated for a single brain met and another nearly 900 treated for 2-4 brain mets during the same time period. As you might expect, there was an inverse correlation with median overall survival: 15 months for those with 1 met, 10 months with 2-4 mets, and 7 months with 5-15 mets, though this didn’t play out to be significant on multivariate analysis. Distant brain failure and brain met velocity also trended as expected, increasing with increasing number of initial brain mets. Importantly, cumulative rates of salvage whole brain radiation were similar (12-16%) and median time to salvage was 8 months for those with initially 1 met and 5 months for those with either 2-4 or 5-15 mets.
Bottom Line: Number of initial brain mets denotes likelihood of subsequent brain mets but not the overall clinical course, and it shouldn’t in itself preclude radiosurgery candidacy. | Hughes, Int J of Radiat Oncol Biol Phys 2019