Treatment outcomes and dose rate effects following gamma knife stereotactic radiosurgery for vestibular schwannomas
Reviewed by Gauri Mankekar

Gamma knife radiosurgery (GKRS) is one of the definitive stereotactic radiotherapy treatment modalities for vestibular schwannoma (VS) management. Its efficacy depends on the cobalt-60 source which has a half-life of 5.26 years. According to the study authors, the actual rate of how quickly fixed radiation doses are delivered during GKRS varies during the lifespan of the cobalt sources and the treatment dose rates vary significantly depending on the age of the cobalt source. Therefore, the authors hypothesised that dose rate effects might influence local control and late toxicity rate after GKRS. The results of their retrospective study of 419 patients with two dose rate groups showed that effective control of VS tumour control was independent of the dose rate but patients who received lower dose rates of single fraction GKRS had significantly better freedom from progressive post-treatment hearing loss and facial nerve dysfunction. The authors caution that late toxicities after GKRS continue to be an important concern despite the fact that GKRS is an extremely precise treatment option and provides highly selective dose distribution with minimum radiation exposure of surrounding normal tissue. This study adds to the literature on GKRS for the treatment of VS.

Impact of Gamma Knife Stereotactic radiosurgery dose rates on functional outcomes.
Smith DR, Saadatmand HJ, Wu C-C, et al.
NEUROSURGERY
2019:85:E1084-94.