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Updated: Nov 8, 2025
A Unified Methodological Framework for Vestibular Schwannoma Research
Published on: June 20, 2017
Optimal Volume of the Residual Tumor to Predict Long-term Tumor Control Using Stereotactic Radiosurgery after Facial
Won Jae Lee1, Jung Il Lee1, Jung Won Choi1
1Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Background:
Intended subtotal resection (STR) followed by adjuvant gamma knife radiosurgery (GKRS) has emerged as an effective treatment option for facial nerve (FN) preservation in vestibular schwannomas (VSs). This study aimed to identify the optimal cut-off volume of residual VS to predict favorable outcomes in terms of both tumor control and FN preservation.
Methods:
This retrospective study assessed the patients who underwent adjuvant GKRS for residual VS after microsurgery. A total of 68 patients who had been followed up for ≥ 24 months after GKRS were included. Tumor progression was defined as an increase in tumor volume (TV) of ≥ 20%. House-Brackmann grades I and II were considered to indicate good FN function.
Results:
The median residual TV was 2.5 cm³ (range: 0.3-27.4). The median follow-up period after the first adjuvant GKRS was 64 months (range: 25.7-152.4). Eight (12%) patients showed tumor progression. In multivariate analyses, residual TV was associated with tumor progression (P = 0.003; hazard ratio [HR], 1.229; 95% confidence interval [CI], 1.075-1.405). A residual TV of 6.4 cm³ was identified as the cut-off volume for showing the greatest difference in progression-free survival (PFS). The 5-year PFS rates in the group with residual TVs of < 6.4 cm³ (54 patients) and that with residual TVs of ≥ 6.4 cm³ (14 patients) were 93.3% and 69.3%, respectively (P = 0.014). A good FN outcome was achieved in 57 (84%) patients. Residual TV was not associated with good FN function during the immediate postoperative period (P = 0.695; odds ratio [OR], 1.024; 95% CI, 0.908-1.156) or at the last follow-up (P = 0.755; OR, 0.980; 95% CI, 0.866-1.110).
Conclusion:
In this study, residual TV was associated with tumor progression in VS after adjuvant GKRS following STR. As preservation of FN function is not correlated with the extent of resection, optimal volume reduction is imperative to achieve long-term tumor control. Our findings will help surgeons predict the prognosis of residual VS after FN-preserving surgery.
Insights
For vestibular schwannoma (VS) treatment, residual tumor volume after subtotal resection (STR) and gamma knife radiosurgery (GKRS) significantly impacts tumor control. Facial nerve preservation is not linked to resection extent, emphasizing optimal volume reduction for long-term success.
Area of Science:
- Neurosurgery
- Radiation Oncology
- Otolaryngology
Background:
- Subtotal resection (STR) followed by adjuvant gamma knife radiosurgery (GKRS) is a key treatment for vestibular schwannomas (VS), aiming for facial nerve (FN) preservation.
- Identifying optimal residual VS volume is crucial for predicting outcomes in tumor control and FN function.
Purpose of the Study:
- To determine the ideal cut-off volume of residual VS after STR and GKRS.
- To correlate residual VS volume with tumor progression and FN preservation.
- To aid surgeons in predicting prognosis after VS surgery.
Main Methods:
- Retrospective analysis of 68 patients undergoing adjuvant GKRS for residual VS post-microsurgery.
- Minimum 24-month follow-up post-GKRS.
- Tumor progression defined as ≥20% increase in tumor volume (TV); good FN function defined as House-Brackmann grades I-II.
Main Results:
- Median residual TV was 2.5 cm³; median follow-up was 64 months.
- Residual TV was significantly associated with tumor progression (HR 1.229, P=0.003).
- A cut-off residual TV of 6.4 cm³ predicted progression-free survival (PFS); 5-year PFS was 93.3% (<6.4 cm³) vs. 69.3% (≥6.4 cm³).
- Good FN outcome achieved in 84% of patients; residual TV did not correlate with FN function.
Conclusions:
- Residual VS volume after STR and adjuvant GKRS is a significant predictor of tumor progression.
- Optimal volume reduction is essential for long-term tumor control, independent of facial nerve preservation.
- Findings assist surgeons in prognosticating residual VS after FN-preserving surgery.
