What planning and dose constraints are you using for 5-fraction hypofractionated FRST for vestibular schwannoma?

When using fractionated SRS (fSRT) of 25 Gy in 5 fractions for vestibular schwannomas, I use only 2 constraints: the brain stem and the cochlea, if the patient has serviceable hearing. In this case, the only OAR needed is the brain stem, 23 Gy <0.5 cc. I don't worry about the trigeminal nerve as it is rare to have complications with the 5th CN, and the TGN is often targeted with much higher doses when treating trigeminal neuralgia (60-90 Gy).

The brain stem constraint of V23 Gy is influenced by R...

Great question. An important consideration is also the amount of time they have had no serviceable hearing, and what that actually means. If they still have sensorineural hearing of any frequency (even very low), they can sometimes regain some hearing function following treatment.

I always default to 25/5. This is one of the only radiosurgical situations in which I keep the dose homogeneous (Dmax <27.5 Gy). This reduces the risk of an early inflammatory response, which is what predisposes patien...

For a 5-fraction FSRS regimen, a more conservative cochlear Dmax of ≤8 Gy (based on radiobiologic modeling with an α/β of 2.0) would be considered reasonable. This corresponds to a biologically effective dose (BED) and EQD2 comparable to a single-fraction cochlear Dmax of 4 Gy levels associated with a lower risk of sensorineural hearing loss. In clinical experience, actual delivered cochlear doses can exceed intended constraints; incorporating centralized QA, protocol-driven contouring, and plan...