For those in the pre -treatment research phase, the most recent Stanford study for CK using a mutli-session protocol (aka fractions) has recently completed the peer review process and been published in the journal of neurosurgery. This is a continuation of the 2005 study which expands the patient universe and follow up period. Between 1999-2007 Stanford has treated 474 AN patients by CK using fractions ( does not include those they did with one shot) and the study is comprised of 383 which had follow up > 1 year and an average follow up period of 3.5 years with a range of 1-10. In general results for tumor kill %, facial and hearing preservation rates are essentially the same as reported in the initial study. My understanding is that this is the largest study to date on both CK and multi-session results
Dr. Chang provided me with a copy of the complete study, so feel free to message / e-mail me separately if you are interested in any more details
The study summary is as follows:
Multisession Stereotactic Radiosurgery for
Vestibular Schwannomas: Single-Institution
Experience With 383 Cases
BACKGROUND: Single-session stereotactic radiosurgery (SRS) treatment of vestibular
schwannomas results in excellent tumor control. It is not known whether functional
outcomes can be improved by fractionating the treatment over multiple sessions.
OBJECTIVE: To examine tumor control and complication rates after multisession SRS.
METHODS: Three hundred eighty-three patients treated with SRS from 1999 to 2007 at
Stanford University Medical Center were retrospectively reviewed. Ninety percent were
treated with 18 Gy in 3 sessions, targeting a median tumor volume of 1.1 cm3 (range,
0.02-19.8 cm3).
RESULTS: During a median follow-up duration of 3.6 years (range, 1-10 years), 10 tumors
required additional treatment, resulting in 3- and 5-year Kaplan-Meier tumor control
rates of 99% and 96%, respectively. Five-year tumor control rate was 98% for tumors ,
3.4 cm3. Neurofibromatosis type 2–associated tumors were associated with worse tumor
control (P = .02). Of the 200 evaluable patients with pre-SRS serviceable hearing AQ : 2
(Gardner-Robertson grade 1 and 2), the crude rate of serviceable hearing preservation
was 76%. Smaller tumor volume was associated with hearing preservation (P = .001).
There was no case of post-SRS facial weakness. Eight patients (2%) developed trigeminal
dysfunction, half of which was transient.
CONCLUSION: Multisession SRS treatment of vestibular schwannomas results in an
excellent rate of tumor control. The hearing, trigeminal nerve, and facial nerve function
preservation rates reported here are promising.
KEY WORDS: Acoustic neuroma, CyberKnife, Fractionated radiotherapy, Hearing preservation, Radiosurgery
