Dose does it.
Do we have a satisfactory answer yet on why whole brain radiation resulted in higher local control rates than stereotactic radiosurgery (SRS) for resected brain mets in a randomized trial? This meta-analysis, including said trial, shows indeed it appears to all come down to tumor size and dose. For instance, in the concurrent randomized trial of post-op SRS versus observation, SRS (16Gy/1) for tumors <2.5 cm pre-op achieved a 91% local control rate at one year. In addition, retrospective data reports hypofractionated SRS (27Gy/3) for cavities >3cm can also achieve excellent local control: 93% at one year and 84% at two years. Taken together with demonstrated better neurocognitive outcomes with post-op SRS versus whole brain radiation, the authors conclude sufficiently-dosed post-op SRS should be the standard for resected brain mets. | Redmond, Int J Radiat Oncol Biol Phys 2021