Advice
Clinical and technical evidence
Clinical and technical evidence
A literature search was carried out for this briefing in accordance with the interim process and methods statement for medtech innovation briefings. This briefing includes the most relevant or best available published evidence relating to the clinical effectiveness of the technology. Further information about how the evidence for this briefing was selected is available on request by contacting mibs@nice.org.uk.
Published evidence
Six studies are summarised in this briefing. This comprises 1 systematic review and meta-analysis, 2 systematic reviews, 2 retrospective observational studies and 1 prospective observational study. This evidence includes a total of 224 people who had brain surgery using the ViewSite Brain Access System (VBAS).
Other published studies were identified including 3 small case series (Eichberg et al. 2020; Okasha et al. 2021 and Valarezo-Chuchuca et al. 2021) and a single patient case study (Hajtovic et al. 2021) but they have not been detailed further in this briefing.
The clinical evidence and its strengths and limitations is summarised in the overall assessment of the evidence.
Overall assessment of the evidence
Evidence from systematic reviews suggests that VBAS may be safe and efficacious for use during surgery for deep-seated brain lesions. Outcomes reported included extent of resection and complication rates. Gross total resection (GTR) reported across the studies included in this briefing ranged from 27% to 72%, and total complication rate ranged from 2.8% to 35%. Evidence suggests that complication rates may be similar for the different tubular retractors. Comparison of GTR between different retractors has limitations because it is a subjective measure and may differ in its definition between studies. The primary evidence for VBAS is limited in quality and mainly comes from single-centre retrospective observational studies with relatively small sample sizes. There is limited primary evidence comparing VBAS with conventional self-retaining spatula-based retractors or other tubular retractors. Although the evidence base includes people aged between 15 months and 86 years, most of the evidence comes from an adult population.
There is no evidence on VBAS from an NHS setting but the experts suggested that outcomes from non-UK studies are likely to be generalisable to the NHS.
Further evidence on the efficacy and safety of the technology in children would be helpful because their postoperative morbidity, mortality, prognosis and outcomes can differ from adults. Multicentre, prospective comparative studies or randomised controlled trials would be helpful in determining the comparative benefits of VBAS compared with conventional self-retaining spatula-based retractors and other tubular retractors. These studies would preferably be in an NHS setting and include outcomes that demonstrate potential reductions in resource use, such as reduced operating times, length of intensive care unit stay, and postoperative hospital stay.
Echeverry et al. (2020)
Intervention and comparator(s)
The systematic review included 3 different brain retractor systems: VBAS (12 studies), BrainPath (29 studies) and METRx (3 studies).
Key outcomes
A total of 426 procedures were done across all studies (289 for BrainPath, 106 for VBAS and 31 for METRx). Types of procedures included biopsy, tumour resection, haematoma evacuation, foreign body removal, and colloid cyst excisions. BrainPath had statistically significantly higher rates of GTR (80.2%) compared with VBAS (59.6%). VBAS had the highest rate of suboptimal tumour resection (STR; 40.4% compared with 19.7% for BrainPath). Over 90% of haematoma evacuations were achieved in all attempts using VBAS. Rates of haematoma evacuation were statistically significantly higher with VBAS compared with BrainPath (p<0.001). The overall complication rate for all retractors was 7.7% and the overall mortality was 3.8%. There was no difference in complication rates (p=0.627) or mortality (p=0.204) among the 3 retractors.
Strengths and limitations
The search strategy appeared appropriate and included both database searches and other sources (company websites), but the date range of the searches was not reported. Reasons for excluding each study were reported. The review states that 4 reviewers critically appraised the studies, but it is unclear whether these reviewers were independent and blinded during the study selection and appraisal process. There was limited discussion on the level of evidence but the authors state that most of the studies included in the review were case–control or retrospective analyses. The study could not determine average lesion size for the retractors because parameters for this measure differed among studies.
Marenco-Hillembrand et al. (2020)
Intervention and comparator(s)
This systematic review included evidence on 4 different tubular retractors: VBAS (3 studies), BrainPath (6 studies), METRx (3 studies) and modified retractors (2 studies).
Key outcomes
The systematic review and meta-analysis included a total of 309 people who were operated on between 2008 and 2018. The pooled prevalence for GTR was 75% (95% confidence interval, 69% to 80%; I2 = 9%). The rates of GTR were similar between high-grade and low-grade gliomas (p=0.45). GTR was more likely to be achieved with metastases than gliomas (p<0.006 for high-grade and p=0.002 for low-grade gliomas). None of the retractors had better GTR rates (p>0.05). The pooled prevalence of complications was 9% (95% confidence interval 6% to 14%; I2 = 0%). A total of 21 people experienced postoperative complications, 13 of which were neurological. All but 3 neurological complications were transient and there were no postoperative central nervous system infections. The number of complications among the different types of retractors was similar.
Strengths and limitations
The study was a systematic review and meta-analysis and provides evidence on pooled GTR and postoperative complication rates. The evidence was reviewed by 2 independent investigators and disagreements were judged by a third reviewer. It used a defined inclusion and exclusion criteria and reasons for excluding studies were reported.
The systematic review included evidence on other tubular retractors and only 3 of the 13 studies were on VBAS. The studies only included data on adults so results may not be generalisable to children. The authors state that preoperative and postoperative lesion volumes, Karnofsky Performance Status, the presence of intraoperative neuromonitoring, and length of postoperative stay were under reported by the included studies.
Shapiro et al. (2020)
Key outcomes
Twelve publications (including a total of 106 patients aged between 15 months and 85 years) met the inclusion criteria. VBAS was most used for tumour resection (55 people), colloid cyst removal (13 people), foreign body removal (6 people) and haematoma evacuation (23 people). The overall complication rate associated with VBAS was 2.8%. Three people experienced short-term postoperative complications that resolved within 6 months (2 people had transient memory loss and 1 person had postoperative tract damage). GTR was achieved in 63% of tumour resections, and subtotal resection was achieved in 37%. All cysts, foreign bodies, and hematomas were successfully removed.
Strengths and limitations
The review states that 4 reviewers critically appraised the studies, but it is unclear whether these reviewers were independent and blinded during the study selection and appraisal process. The authors state that most of the studies included in the systematic review were case–control or retrospective analyses and were not designed to assess adverse outcomes specific to VBAS or to provide direct comparisons between tubular retractor systems. Lesion volumes were not reported in all studies so average lesion size could not be calculated. The longest follow up for complication rates reported in the studies was around 6 months.
Eichberg et al. (2020)
Key outcomes
A total of 113 people who were operated on between August 2013 and April 2019 from 3 centres were included. GTR was achieved in 71.7% of people (n=81), near total resection in 10.6% (n=12), maximal safe resection in 7.1% (n=8), and subtotal resection in 8.8% (n=10). The permanent complication rate was 4.4% (n=5). One person had a seizure within a week after surgery and no late seizures (after the 1‑week follow up) were reported. Mean length of hospital stay after surgery was 4.1 days. Lesions resected using BrainPath were deeper than lesions resected with VBAS (4.8 cm [range 1.6 cm] compared with 3.9 cm [range 2.3 cm]; p=0.022). VBAS was more frequently used in cavernoma resection (p=0.015) and BrainPath was more frequently used in glioma (p=0.014) and metastatic tumour resections (p=0.013). There was no statistically significant difference in the extent of resection, rate of immediate complications or postoperative length of hospital stay between the 2 retractors.
Strengths and limitations
The study included the largest number of people to date and included multiple centres and surgeons. The extent of resection was measured by a board-certified neurosurgeon who was blinded to the treatment.
The study was retrospective and non-randomised. Comparisons between the 2 retractors were not propensity score matched so heterogeneity in the study population may have prevented a true comparison of effectiveness. The study included adults aged 18 to 85 so results may not be generalisable to children. The study did not compare tubular retractors to conventional self-retaining spatula-based retractors.
Capitanio et al. (2020)
Key outcomes
The study included 20 people who had ultrasound and MRI‑navigated transcortical surgery using VBAS between January 2012 and December 2017. The age range was 15 to 71 years. Gross total removal was achieved in 70% of people (n=14). The mean duration of surgery was 225.9 plus or minus 59 minutes. No critical events, major bleedings or intraoperative deaths were reported. One person experienced a postoperative cerebrospinal fluid infection. Permanent neurological adverse effects were reported in 30% of people (n=6), including cognitive decline (n=3), memory deficits (n=2) and behavioural alterations (n=1). The mean Functional Independence Measure (FIM) score at last follow up was 105 (ranging from 65 to 124).
Shashivadhanan (2020)
Intervention and comparator(s)
VBAS. Outcomes were compared with a historical control group which shared a similar clinical profile. The control group was operated on using conventional retractor blades.
Key outcomes
The study included a total of 22 people who underwent surgery between April 2015 and July 2018. The lesion types included intracerebral haemorrhage (45%), colloid cyst (95%), high-grade glioma (27%), cystic tumours (9%) and metastasis (9%). Total excision was achieved in 27% of people and 90% excision was achieved in 45% of people. The overall complication rate was 13%. No retractor-induced infarction was reported with VBAS compared with 8% in the historical controls. Use of VBAS was also associated with a reduced need for steroids and cerebral decongestants after surgery. The ease of surgery and time taken were similar in both groups.
Strengths and limitations
The study involved a historical control group comparing VBAS with conventional retractor blades. However, no comparative statistical analyses were reported. There was very limited information on the demographics of the 2 groups. The study was retrospective in design, done at a single centre, and had a relatively small sample size.