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Top Line: Whoever coined the name Gamma Knife (GK) over half a century ago sure knew what they were doing from a marketing standpoint.
The Study: The excitement following installation of a brand-new, top-of-the-line linear accelerator (LINAC) with all the bells and whistles (e.g., high-def MLCs, 6DoF couch, you name it) can be short-lived when your next patient says: that’s great, but do you have a “Gamma Knife”..? This retrospective study asks, beyond the obvious perks in patient convenience with LINAC-based radiosurgery—no head frame, no sedation, a fraction of time required on the table, etc—whether there are any differences in intracranial toxicity following LINAC versus GK radiosurgery for multiple brain mets. Cases were pulled from two institutions, each employing a different technique. LINAC-based treatment (n=1014 lesions) used the streamlined single iso multitarget technique with a 1-2 mm planning margin on intact mets and 2-3 mm margin post-op. GK treatment (n=1685 lesions) used single or multi-iso techniques prescribing to the 50% isodose line with no margin on either intact or post-op cases. After propensity score matching for tumor location, total treatment volume, and dose / fractionation, GK treatment was found to be a significant predictor of radionecrosis (HR 3.8), along with prior whole-brain treatment (HR 2.5) and number of target lesions. This persisted when comparing GK to only single-fraction LINAC treatments (HR 4.4).
TBL: Higher central doses with GK may result in higher rates of radionecrosis than increased lower dose distributions with LINAC-based radiosurgery. P.S. Can someone please popularize a catchier name? | Sebastian, Radiother Oncol 2020