For which patients is frameless gamma knife radiosurgery most appropriate?

Patients who are good candidates are those with tumors that obviously need fractionation (large size, near optic chiasm, etc.) AND are very compliant / able to participate in their care. Noncompliant patients will be impossible - there will be too much motion. It's difficult for most patients to tolerate more than 45 minutes in the mask. Using the frame is desired for anything which more than 1mm-1.5mm excursion is unacceptable (TGN, functional neurosurgery, single fraction pituitary treatment) or for which treatment time is prolonged (multiple metastases). Most centers report they use the frameless system for 5-10% of their volume relative to using the frame. We have yet to treat acoustic neuromas with this system, but I'm enthusiastic abo...

There is not a set answer

It matters on the pathology being treated. size and location of the tumor as well as the equipment being utilized. Frame can help reduce margin, increase accuracy of certain systems and allow for fractionation.

Regarding brain metastases Minniti published on fractionation for tumors >2cm (https://www.ncbi.nlm.nih.gov/pubmed/27209508) with improved local control and reduced necrosis. They utilized 8 Gy x 3 but I would estimate that 30-35 Gy in 5 fractions would likely provide similar outcomes. Of note they changed the margin size and went from 2mm -> 1mm. This is important distinction as isocentricity of your LINAC will alter which patients are marginal candidates for frameless.

Generally, I've used either isocentricit...