***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE The world 's first Leksell Gamma Knife PerfeXion ( Elekta Instrument AB , Stockholm , Sweden ) for radiosurgery of the head and neck became operational at Timone University Hospital in Marseille on July 10 , 2006 . To allow strict evaluation of the capabilities , advantages , disadvantages , and limitations of this new technology , patients were enrolled in a prospect i ve , r and omized trial . METHODS In 66 working days , between July 10 and December 20 , 2006 , 363 patients were treated by gamma knife surgery at Timone University Hospital , Marseille . Of these patients , 200 were eligible for the comparative prospect i ve study ( inclusion criteria were informed consent obtained , tumor or vascular indication , and no previous radiosurgery or radiotherapy ) . In accordance with the blinded r and omization process , 100 patients were treated with the Leksell Gamma Knife 4C ( Elekta Instrument AB ) and Gamma Knife 100 ( Elekta Instrument AB ) with the Leksell Gamma Knife PerfeXion .  Dose planning parameters , dosimetry measurements on the patient 's body , workflow , patient comfort , quality assurance procedure , and a series of other treatment-related parameters were systematic ally and prospect ively evaluated in both arms of the trial . RESULTS No technical failure of the treatment procedure was encountered . The new dose-planning system led to the use of composite shots in 39.4 % of the patients . The median number of different collimator sizes used was larger with the PerfeXion than with the 4C ( 2 and 1 , respectively ) . The mean number of isocenters used was lower ( 10.67 and 13.08 , respectively ) . The median total treatment time was significantly shorter with the PerfeXion ( 40 and 60 minutes , respectively ) , but there was no significant difference in the median radiation time ( 34.02 and 33.40 minutes , respectively ) . The procedure was performed using only a single run in 98.99 % of the PerfeXion cases and in 42 % of the 4C cases . Collision risk on the 4C forced us to change the frame gamma angle for at least 1 shot in 24 % of the patients and led to treatment in manual mode for at least 1 shot in 21 % of the patients . Collision risk requiring technical adaptation did not occur with the PerfeXion . In 1 patient treated with the PerfeXion , the system required a direct collision check . In terms of dose to structures outside the target area , the PerfeXion delivers 8.2 times less to the vertex , 10 times less to the thyroid , 12.9 times less to the sternum , and 15 times less to the gonads . CONCLUSION Our prospect i ve study indicates that procedures with the PerfeXion were collision-free , even with very eccentric lesions ( e.g. , multiple metastases ) . The duration of the surgical procedure , the amount of time required for nurse , physicist , and physician intervention on the machine , and the duration of the quality assurance procedure were all shown to be dramatically reduced with the PerfeXion gamma knife . Patient protection is greatly improved with the PerfeXion . In our experience , the technological advances of the Leksell Gamma Knife PerfeXion will make a very significant contribution to future progress in head and neck radiosurgery BACKGROUND Single-fraction radiosurgery of acoustic neuromas less than 3 cm in diameter is remarkable for high control but not infrequent incidence of facial and trigeminal neuropathy . Larger tumors treated surgically often result in deafness and facial neuropathy . Fractionated stereotactic radiosurgery was used in an effort to maintain effective therapy while minimizing toxicity of treatment . METHODS The authors described 38 patients with acoustic neuromas , with age range 35 - 89 years ( mean , 60 years ) .  2,000 cGy in divided weekly doses of 400 or 500 cGy was most commonly prescribed . Tumors > or = 3 cm ( n = 16 ) received the 5 fraction schema . Mean tumor volume was 6.9 cm3 , with range from 0.1 to 32.0 cm3 . RESULTS Median clinical follow-up was 27.1 months , while neuroimaging follow-up had a median of 16.3 months . All tumors were controlled . Of 23 tumors smaller than 3 cm , 14 ( 61 % ) decreased in size , and 9 showed cessation of growth . Thirteen of 16 ( 81 % ) large acoustic neuromas ( 3 - 5 cm ) diminished in size . The remaining 3 showed cessation of growth . Median radiographic follow-up was 20 months , with a median clinical follow-up of 28 months . No patient developed fifth nerve symptoms after treatment nor did any patient require surgery for treatment failure . Only one had temporary seventh nerve palsy . CONCLUSION Fractionated stereotactic radiosurgery offers a therapeutic approach producing high control rates while avoiding morbidity frequently seen after single-fraction radiosurgery or microsurgery OBJECT Small vestibular schwannomas ( VSs ) are often conservatively managed and treated only upon growth . Growth is usually reported in mm/year , but describing the growth of a 3D structure by a single diameter has been question ed . As a result , VS growth dynamics should be further investigated . In addition , baseline clinical parameters that could predict growth would be helpful . In this prospect i ve study the authors aim ed to describe growth dynamics in a cohort of conservatively managed VSs . They also compared different growth models and evaluated the ability of baseline parameters to predict future growth . METHODS Between 2000 and 2006 , 178 consecutive patients with unilateral de novo small-sized VSs identified among the Norwegian population of 4.8 million persons were referred to a tertiary care center and were included in a study protocol of conservative management . Tumor size was defined by MR imaging-based volume estimates and was recorded along with clinical data at regular visits . Mixed-effects models were used to analyze the relationships between observations . Three growth models were compared using statistical diagnostic tests : a mm/year-based model , a cm(3)/year-based model , and a  volume doubling time  (VDT)-based model . A receiver operating characteristic curve analysis was used to determine a cutoff for the VDT-based model for distinguishing growing and nongrowing tumors . RESULTS A mean growth rate corresponding to a VDT of 4.40 years ( 95 % CI 3.49 - 5.95 ) was found . Other growth models in this study revealed mean growth rates of 0.66 mm/year ( 95 % CI 0.47 - 0.86 ) and 0.19 cm(3)/year ( 95 % CI 0.12 - 0.26 ) . Volume doubling time was found to be the most realistic growth model . All baseline variables had p values > 0.09 for predicting growth . CONCLUSIONS Based on the actual measurements , VDT was the most correct way to describe VS growth . The authors found that a cutoff of 5.22 years provided the best value to distinguish growing from nongrowing tumors . None of the investigated baseline predictors were usable as predictors of growth OBJECTIVE The best management for patients with small- to medium-sized vestibular schwannomas ( VS ) is controversial . METHODS : A prospect i ve cohort study of 82 patients with unilateral , unoperated VS less than 3 cm undergoing surgical resection ( n = 36 ) or radiosurgery ( n = 46 ) . Patients undergoing resection were younger ( 48.2 yr versus 53.9 yr , P = 0.03 ) . The groups were similar with regard to hearing loss , associated symptoms , and tumor size . The mean follow-up period was 42 months ( range , 12 - 62 mo ) . RESULTS Normal facial movement and preservation of serviceable hearing was more frequent in the radiosurgical group at 3 months ( P < 0.001 ) , 1 year ( P < 0.001 ) , and at the last follow-up examination ( P < 0.01 ) compared with the surgical resection group . Patients undergoing surgical resection had a significant decline in the following subscales of the Health Status Question naire 3 months after surgery : physical functioning ( P = 0.006 ) , role-physical ( P < 0.001 ) , energy/fatigue ( P = 0.02 ) , and overall physical component ( P = 0.004 ) . Patients in the surgical resection group continued to have a significant decline in the physical functioning ( P = 0.04 ) and bodily pain ( P = 0.04 ) subscales at 1 year and in bodily pain ( P = 0.02 ) at the last follow-up examination . The radiosurgical group had no decline on any component of the Health Status Question naire after the procedure . The radiosurgical group had lower mean Dizziness H and icap Inventory scores ( 16.5 versus 8.4 , P = 0.02 ) at the last follow-up examination . There was no difference in tumor control ( 100 versus 96 % , P = 0.50 ) . CONCLUSION Early outcomes were better for VS patients undergoing stereotactic radiosurgery compared with surgical resection ( Level 2 evidence ) . Unless long-term follow-up evaluation shows frequent tumor progression at currently used radiation doses , radiosurgery should be considered the best management strategy for the majority of VS patients BACKGROUND There are few reports about the course of vestibular schwannoma ( VS ) patients following gamma knife radiosurgery ( GKRS )  compared with the course following conservative management ( CM ) . In this study , we present prospect ively collected data of 237 patients with unilateral VS extending outside the internal acoustic canal who received either GKRS ( 113 ) or CM ( 124 ) . OBJECTIVE The aim was to measure the effect of GKRS compared with the natural course on tumor growth rate and hearing loss . Secondary end points were post inclusion additional treatment , quality of life ( QoL ) , and symptom development . METHODS The patients underwent magnetic resonance imaging scans , clinical examination , and QoL assessment by SF-36 question naire . Statistics were performed by using Spearman correlation coefficient , Kaplan-Meier plot , Poisson regression model , mixed linear regression models , and mixed logistic regression models . RESULTS Mean follow-up time was 55.0 months ( 26.1 st and ard deviation , range 10 - 132 ) . Thirteen patients were lost to follow-up . Serviceable hearing was lost in 54 of 71 ( 76 % ) ( CM ) and 34 of 53 ( 64 % ) ( GKRS ) patients during the study period ( not significant , log-rank test ) . There was a significant reduction in tumor volume over time in the GKRS group . The need for treatment following initial GKRS or CM differed at highly significant levels ( log-rank test , P < .001 ) . Symptom and QoL development did not differ significantly between the groups . CONCLUSION In VS patients , GKRS reduces the tumor growth rate and thereby the incidence rate of new treatment about tenfold . Hearing is lost at similar rates in both groups . Symptoms and QoL seem not to be significantly affected by GKRS OBJECTIVE To conduct a prospect i ve , open , nonr and omized study of treatment-associated morbidity in patients undergoing microsurgery or gamma knife radiosurgery ( GKRS ) for vestibular schwannomas . METHODS Ninety-one patients with vestibular schwannomas with a maximum tumor diameter of 25 mm in the cerebellopontine angle were treated according to a prospect i ve protocol either by  GKRS  ( 63 patients ) or open microsurgery ( 28 patients ) using the suboccipital approach . Primary end points included hearing function , according to the Gardner-Robertson scale , and facial nerve function , according to the House-Brackmann scale at 2 years . Clinical data included a balance platform test , score for tinnitus and vertigo using a visual analog scale , and working ability . Patients responded to the quality -of-life question naires Short-Form 36 and Glasgow Benefit Inventory . RESULTS Three elderly GKRS patients withdrew ; all remaining patients were followed for 2 years . Both primary end points were highly significant in favor of GKRS ( P < 0.001 ) . Evidence of reduced facial nerve function ( House-Brackmann grade 2 or poorer ) at 2 years was found in 13 of 28 open microsurgery patients and 1 of 60 GKRS patients . Thirteen of 28 patients who underwent surgery had serviceable hearing ( Gardner-Robertson grade A or B ) preoperatively , but none had serviceable hearing postoperatively . Twenty-five of 60 GKRS patients had serviceable hearing before treatment , and 17 ( 68 % ) of them had serviceable hearing 2 years after treatment . The tinnitus and vertigo visual analog scale score , as well as balance platform tests , did not change significantly after treatment , and working status did not differ between the groups at 2 years . Quality of life was significantly better in the GKRS group at 2 years , based on the Glasgow Benefit Inventory question naire . One GKRS patient required operative treatment within the 2-year study period . CONCLUSION This is the second prospect i ve study to demonstrate better facial nerve and hearing outcomes from GKRS than from open surgery for small- and medium-sized vestibular schwannomas 
    Output:
    
There is no high quality evidence in the literature from RCTs to determine whether  stereotactic radiotherapy  is better than  microsurgical resection or observation alone  for patients with a vestibular schwannoma .