Gamma knife treatment of growing vestibular schwannoma in Norway: a prospective study.
OBJECTIVE
Gamma Knife radiosurgery (GKRS) has been increasingly used in the treatment of vestibular schwannoma (VS). Very few studies relate tumor control and post-treatment growth rates to pretreatment growth rates.


METHODS
We prospectively included 45 consecutive VS patients who were initially treated conservatively and then received GKRS between 2000 and 2007 because of demonstrated tumor growth. Pretreatment and post-treatment tumor volumes were estimated. Patients underwent audiograms, reported their symptoms, and responded to the Short Form General Health Survey (SF-36) questionnaire on each visit.


RESULTS
Volume doubling times before and after treatment were 1.36 years (95% confidence intervals, 1.14-1.68) and -13.1 years (95% confidence intervals, -111.0 to -6.94), respectively. Tumor control, defined as a post-GKRS growth rate ≤ 0, was achieved in 71.1% of patients, with highest odds for tumor control among older patients and those with larger tumors. The 5-year retreatment-free survival rate was 93.9% (95% confidence intervals, 76.5-98.5). None of the clinical endpoints investigated showed statistically significant changes after GKRS, but improvement was seen in a few SF-36 parameters.


CONCLUSIONS
GKRS alters the natural course of the tumor by reducing growth. Mathematic models yield poorer tumor control rates than those found by clinical assessment. Symptoms were unaffected by treatment, but quality of life was improved.
Institute of Surgical Sciences, University of Bergen, Bergen, Norway. jobinv@gmail.com
Jobin Kotakkathu
JK
Varughese
Tore
T
Wentzel-Larsen
Paal-Henning
PH
Pedersen
Ruby
R
Mahesparan
Morten
M
Lund-Johansen
D000328:Adult; D000368:Aged; D018572:Disease-Free Survival; D005260:Female; D006309:Hearing / Q000528:radiation effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D009664:Norway; D011446:Prospective Studies; D011788:Quality of Life; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D019233:Retreatment; D011795:Surveys and Questionnaires; D013997:Time Factors; D047368:Tumor Burden / Q000502:physiology / Q000528:radiation effects*