Long-term clinical outcomes of stereotactic radiosurgery and hypofractionated stereotactic radiotherapy using the CyberKnife® robotic radiosurgery system for vestibular schwannoma

Transforming Brain Tumor Care: The Global Impact of Radiosurgery in Multidisciplinary Treatment Over Two Decades

BACKGROUND

Stereotactic radiosurgery, a minimally invasive treatment delivering high doses of radiation to a well-defined target, has transformed interdisciplinary treatment paradigms since its inception. This study chronicles its adoption and evolution for brain cancer and tumors globally.

METHODS

A systematic literature review of SRS-focused articles from 2000 to 2023 was conducted. Literature impact was evaluated using citation counts and relative citation ratio scores. Extracted data were dichotomized between US and international publications.

RESULTS

Out of 5424 articles eligible, 538 met inclusion criteria reporting on 120,756 patients treated with SRS for brain cancer and tumors since 2000. Over time, publication rates grew significantly (p = 0.0016), with 56% of principal investigators based in the United States. Clinical articles accounted for 87% of the publications, with the remainder focused on technological advances. Relative to international studies, US publications had larger median samples (74 vs. 58, p = 0.012), higher median citations (30 vs. 19, p < 0.0001) and higher relative citation ratio scores (1.67 vs. 1.2, p < 0.00001). Gamma Knife and LINAC had roughly equal representation in US and international publications. Neurosurgery specialists authored more Gamma Knife-based articles, and radiation oncology specialists authored more LINAC-based papers (p < 0.0001). The most treated tumors were metastases (58%), skull base tumors (35%), and gliomas (7%). Radiographic control was achieved in 82% of metastatic tumor cases, with a 12% median complication rate.

CONCLUSIONS

SRS has been widely adopted both nationally and globally and continues to be a growing field. This study corroborates the clinical efficacy of SRS and reinforces its critical role in the multidisciplinary treatment of patients with brain tumors and cancer.

The safety and efficacy of robotic radiosurgery and radiotherapy in the management of skull base tumors: a systematic review and meta-analysis

Stereotactic radiosurgery (SRS) and radiotherapy (SRT) have gained prominence as both adjuvant and primary treatment options for patients with skull base tumors that are either inoperable or present as residual or recurrent lesions post-surgery. The object of the current study is to evaluate the safety and efficacy of robotic-assisted SRS and SRT across various skull base pathologies. The study was conducted under PRISMA guidelines and involved a comprehensive evaluation of databases, including PubMed, Scopus, Embase, Web-of-Science, and the Cochrane Library. The data collection period was extended up to 30 September. Statistical analyses were executed using Comprehensive Meta-Analysis software. Furthermore, Cochran's Q test assessed statistical heterogeneity within the findings. From an initial pool of 1,792 articles, 69 studies were included in the systematic review, with 60 qualifying for meta-analysis, encompassing 3,046 participants. Meta-analysis revealed tumor control rates were significantly enhanced with the use of CyberKnife (95% CI: 0.901-0.928, p < 0.001) and robotic Gamma Knife radiosurgery (GKRS) (95% CI: 0.897-0.959, p < 0.001). Meningiomas and schwannomas exhibited higher treatment responsiveness (ES: 0.960 and 0.949, respectively), whereas chordomas displayed lower responsiveness (ES: 0.743). The overall major adverse event rate was between 5.6% and 8.3% (95% CI: 0.056-0.083, p < 0.001). Adverse events exhibited a higher incidence in patients with adenomas (95% CI: 0.122-0.217, p < 0.001), while they were least prevalent in those with schwannomas (95% CI: 0.019-0.041, p < 0.001). Robotic SRS and SRT, employing both gamma-knife and cyber-knife, have demonstrated promising outcomes characterized by high efficacy and safety in managing various skull base tumors.

Hearing Function after CyberKnife for Vestibular Schwannoma: A Systematic Review

Introduction  CyberKnife (CK) radiosurgery is a treatment strategy for vestibular schwannoma (VS). Objectives  To evaluate hearing preservation (HP) after CK for VS. Data Synthesis  The study was conducted following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement, and it was registered at the International Prospective Register of Systematic Reviews (PROSPERO, under number CRD42021250300). The inclusion criteria were based on the population, intervention, comparison, outcome, timing and study design (PICOTS) strategy: population - patients with VS; intervention - CK; Comparison - none; Outcome - serviceable HP defined by Gardner and Robertson as grades I or II, or by the American Academy of Otolaryngology and Head and Neck Surgery as classes A or B; timing - mean follow-up longer than 1 year; and study design - retrospective or prospective studies. The exclusion criteria were: studies not published in English; studies published before January 2000 and after October 2021; and studies only including patients with neurofibromatosis type 2 or submitted to a previous treatment. The PubMed/MEDLINE, EMBASE, Web of Science, Cochrane Library, LILACS, and IBECS databases were used and last searched on October 27th, 2021. Statistical heterogeneity was assessed using I 2 statistics. The appraisal checklist was used to assess the risk of bias in the included studies. A total of 222 studies were analyzed, and 13 were included in the synthesis, which represents 493 participants with serviceable hearing before intervention. The mean HP rate after CK using a random effects model was of 68% (95% confidence interval [95%CI]: 59-76%) at a mean follow-up of 42.96 months. Conclusion  The longer follow-up period was associated with a lower HP rate after CK radiosurgery for VS in the qualitative synthesis.

Comparison of Stereotactic Radiosurgery and Hypofractionated Radiosurgery for Vestibular Schwannomas: A Meta-Analysis of Available Literature

BACKGROUND

Stereotactic radiosurgery (SRS) and recently, hypofractionated radiosurgery (hSRS) are increasingly utilized as treatment for vestibular schwannomas (VS). We performed a meta-analysis of literature comparing these modalities.

METHODS

The PubMed database of articles was searched for studies that compared SRS and hSRS in patients with VS. Variables analyzed include tumor control, hearing preservation, facial nerve preservation, trigeminal nerve preservation, and total complications. Heterogeneity across the studies was gauged using Higgins's inconsistency index. Funnel plots and Egger's regression intercept test were used to address the publication bias.

RESULTS

Thirteen studies that satisfied the search criteria were selected for meta-analysis. The studies identified in our study included 353 SRS and 511 hSRS-treated patients. Analysis of heterogeneity showed that hSRS is employed for relatively larger tumor sizes in comparison to SRS. Pooled meta-analysis estimates showed no significant differences between SRS and hSRS in terms of tumor control (odds ratio [OR], 0.620; 95% confidence interval [CI], 0.21-1.86, P = 0.39), hearing preservation (OR, 1.07; 95% CI, 0.59-1.93, P = 0.83), facial nerve preservation (OR, 0.53; 5% CI, 0.23-1.21, P = 0.13), or trigeminal nerve preservation (OR, 0.67; 95% CI, 0.24-1.89, P = 0.49) at a mean follow-up of 39 months. Statistically significant heterogeneity was found across the studies only for tumor diameter (Higgins's inconsistency index = 65.69%, P = 0.003) but not for other variables.

CONCLUSIONS

Meta-analysis of thirteen studies comparing SRS and hSRS as treatment for VS showed comparable tumor control, hearing preservation, facial nerve preservation, and trigeminal nerve preservation.

Long-term clinical outcomes of stereotactic radiotherapy for bilateral vestibular schwannomas in neurofibromatosis type 2 patients

PURPOSE

The evidence for treating patients with neurofibromatosis 2-related vestibular schwannoma (VS-NF2) using hypofractionated stereotactic radiation therapy (HSRT) is limited. This study aimed to investigate clinical outcomes in patients with VS-NF2 treated with Robotic HSRT.

METHODS

We retrospectively analyzed 25 NF2 patients with 48 VSs who were treated using Robotic HSRT at Ramathibodi Hospital from January 2009 to January 2020.

RESULTS

Median follow-up was 98 months (range, 24-155 months). Median tumor volume was 2.3 cm3 (range, 0.4-28.3 cm3). Median prescribed dose was 18 Gy (range, 18-25 Gy) in three fractions (range, 3-5). The 5- and 10-year local control rates were 87% and 80%, respectively. The 5- and 10-year hearing preservation rates were 59% and 35%, respectively. Three patients developed new symptoms associated with transient volume expansion after treatment: hydrocephalus in one, facial weakness in one, and ataxia in one. No patient developed worsening of trigeminal nerve function. No histologically confirmed of radiation induced malignancy was reported in the study.

CONCLUSIONS

Robotic HSRT demonstrated excellent long-term tumor control with a low non-auditory complication rate in patients with VS-NF2. However, preservation of hearing remains a major concern.

Cochlear radiation dose and hearing loss in patients with vestibular schwannoma undergoing radiosurgery: systematic review

OBJECTIVES

To determine the cut-off point of the cochlear radiation dose as a risk factor for hearing loss in patients with vestibular schwannoma treated with radiosurgery.

METHODS

A systematic review of the literature was performed without language or publication year restrictions in the MEDLINE/PubMed, EMBASE, Web of Science, LILACS/VHL and Cochrane Library databases. Studies that met the following criteria were included: 1) population: adults of both sexes who underwent radiosurgery for vestibular schwannoma treatment; 2) exposure: cochlear radiation; 3) outcome: hearing loss; 4) type of study: cohort. Two independent reviewers conducted the entire review process. The registration number in PROSPERO was CRD42020206128.

RESULTS

From the 333 articles identified in the searches, seven were included after applying the eligibility criteria. There was no standardization as to how to measure exposure or outcome in the included studies, and most studies did not present sufficient data to enable meta-analysis.

CONCLUSION

It was not possible to determine a cut-off point for high cochlear dose that could be considered a risk factor for hearing loss.