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Updated: Jul 9, 2025
A Unified Methodological Framework for Vestibular Schwannoma Research
Published on: June 20, 2017
Long-term tumor control in Koos grade IV vestibular schwannomas without the need for gross-total resection
Michel Roethlisberger1,2, Giusi Moffa3, Jonathan Rychen1
1Departments of1Neurosurgery and.
Objective:
The modern management of patients with Koos grade IV vestibular schwannomas (VSs) aims at functional preservation and long-term tumor control. Gross-total resection (GTR) leads to optimal tumor control but frequently also results in permanent facial nerve (FN) palsy. Subtotal resection (STR) or near-total resection (NTR) followed by a wait-and-scan protocol and second-line radiation therapy (RT) in case of progressive residuals yields excellent tumor control rates with less permanent morbidity.
Methods:
The authors present the results of their prospective cohort of Koos grade IV VS patients who underwent less-than-total resection followed by a wait-and-scan protocol between January 2009 and December 2019 and discuss the latest evidence on this controversial subject. The cohort was followed up with annual clinical and volumetric outcome analyses after standardized MRI.
Results:
Forty-eight patients were included in the analysis. The mean extent of resection was 87% (median 91%, range 45%-100%), best fitting into the definition of STR rather than NTR. In 2 cases, the proximal portion of the FN at the brainstem could not be reliably identified and monitored during the initial operation, and a second-stage resection was necessary. At 4.4 years after surgery, 81% (39/48) of the tumor residuals regressed or were stable in size. The percentage of regressive tumor residuals increased over time. Nineteen percent (9/48) of the tumor residuals displayed volumetric progression within a mean time of 35 months (median 36 months, range 14-72 months), resulting in a Kaplan-Meier estimate for progression-free survival of 79% after 4 years; higher postoperative volume showed a linear correlation with higher volumetric progression (factor 1.96, 95% CI 1.67-2.30; p < 0.001). Thirty-four of the 48 (71%) patients continue to undergo a wait-and-scan protocol. Second-line RT was performed in 14 patients (29%) within a mean time of 25 months (median 23 months, range 5-54 months), 12 (86%) of whom responded with post-RT pseudoprogression, resulting in an overall tumor control rate of 96%. At the 4.4-year follow-up from the initial resection, 92% of the patients had a good facial outcome (House-Brackmann [HB] grade I or II), 6% had a fair facial outcome (HB grade III), and 2% had a poor facial outcome (HB grades IV-VI). So far, there has been no need for salvage surgery after RT.
Conclusions:
STR followed by observation and second-line RT in cases of progression leads to good facial outcome and an excellent tumor control rate in the longer term.
Insights
Subtotal resection for large vestibular schwannomas followed by observation and radiation therapy for progression offers excellent tumor control and good facial nerve outcomes.
Area of Science:
- Neurosurgery
- Oncology
- Otolaryngology
Background:
- Management of Koos grade IV vestibular schwannomas (VSs) balances functional preservation with tumor control.
- Gross-total resection (GTR) offers optimal tumor control but often results in permanent facial nerve (FN) palsy.
- Subtotal resection (STR) or near-total resection (NTR) followed by observation and selective radiation therapy (RT) presents an alternative with potentially lower morbidity.
Purpose of the Study:
- To evaluate the efficacy and safety of less-than-total resection for Koos grade IV VSs.
- To assess tumor control rates and facial nerve function following STR/NTR and a wait-and-scan protocol.
- To analyze the role of second-line RT for progressive tumor residuals.
Main Methods:
- Prospective cohort study of 48 patients with Koos grade IV VSs undergoing less-than-total resection (Jan 2009-Dec 2019).
- Follow-up included annual clinical assessments and volumetric MRI analyses.
- Analysis of tumor residual behavior, progression-free survival, facial outcomes (House-Brackmann grade), and RT utilization.
Main Results:
- Mean resection extent was 87% (STR).
- Tumor residuals stabilized or regressed in 81% of patients at 4.4 years; 79% progression-free survival at 4 years.
- Overall tumor control rate reached 96% after selective second-line RT for progression, with 92% achieving good facial outcomes (HB grade I/II).
Conclusions:
- STR followed by observation and selective second-line RT is a viable strategy for Koos grade IV VSs.
- This approach achieves excellent long-term tumor control while preserving facial nerve function.
- It offers a favorable alternative to GTR, minimizing permanent morbidity.
