• Conrad Josef Villafuerte, David B Shultz, Normand Laperriere, Fred Gentili, Robert Heaton, Monique van Prooijen, Michael D Cusimano, Mojgan Hodaie, Michael Schwartz, Alejandro Berlin, David Payne, Suneil K Kalia, Mark Bernstein, Justin Wang, Gelareh Zadeh, Julian Spears, and Derek S Tsang.
• Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada.
• World Neurosurg. 2021 Aug 1; 152: e512-e522.

ObjectiveTo evaluate the relationships between calibration dose rate, calculated biologically effective dose (BED), and clinical factors and tumor control after stereotactic radiosurgery (SRS) for acoustic neuroma.MethodsWe performed a retrospective study of all patients with acoustic neuromas treated with frame-based cobalt-60 SRS at a single institution between 2005 and 2019. The calibration dose rate and cobalt-60 half-life were used to calculate the nominal dose rate during treatment. An SRS-specific monoexponential model accounting for treatment time per lesion was used to estimate BED.ResultsThe study included 607 patients with 612 acoustic neuromas. Median follow-up was 5.0 years. There was no association between dose rate or BED with local failure (LF), radiologic edema, or symptomatic edema. Cystic tumors (adjusted hazard ratio 0.26, P = 0.028) were associated with lower LF, while use of SRS as salvage treatment for growing tumors (adjusted hazard ratio 4.9, P < 0.0001) was associated with higher LF. LF occurred more frequently in larger-diameter tumors, while radiologic or symptomatic edema occurred more frequently in larger-volume tumors.ConclusionsRadiosurgery dose rate and BED were not associated with tumor control or radiologic or symptomatic edema. Salvage SRS and larger tumors were associated with a higher LF rate, while cystic tumors were associated with a lower LF rate. Patients with larger tumors should be counseled appropriately about potential side effects and when to seek follow-up care.Copyright © 2021 Elsevier Inc. All rights reserved.

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