Early Volumetric Response After Stereotactic Radiosurgery in Treatment-Naïve Koos Grade III-IV Cystic Vestibular Schwannomas
In brief
Cystic vestibular schwannomas shrink markedly more than solid tumors after radiosurgery
In a weighted analysis of 15 cystic and 61 solid Koos grade III-IV schwannomas, cystic lesions showed significantly greater volume reduction at 3-6 months and 12-18 months post-SRS, while long-term shrinkage equalized. Local control was 100% for cystic and 98% for solid tumors, supporting SRS as a less invasive option for large cystic VS.
- Journal
- Practical radiation oncology (Q1)
- Published
- 10 September 2026
- Study design
- Cohort / observational study
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Takahiro Sanada, Michael Schulder, Connor Chiu, Nitika Bajaj, Jung Park, Daniel G Eichberg, et al.
- PMID
- 42722232
- DOI
- 10.1016/j.prro.2026.08.010
Why clinicians should know about it
- Picked for Radiation Oncology (paper of the day, 14 September 2026): Early volumetric shrinkage of cystic VS after SRS
Abstract
BACKGROUND: The role of stereotactic radiosurgery (SRS) for large vestibular schwannomas (VS) remains controversial, particularly for patients with cystic VS, which can grow rapidly and are often managed by microsurgical resection. OBJECTIVE: This study aimed to evaluate the volumetric response of cystic VS compared with solid VS following SRS in patients with treatment-naïve Koos grade III-IV tumors. METHODS: This retrospective study included patients with newly diagnosed Koos grade III-IV VS treated with SRS, with > 6 months of radiological follow-up. Tumors were classified as cystic or solid based on pretreatment MRI. Inverse probability of treatment weighting (IPTW) was applied to adjust for baseline differences, and multivariable weighted linear regression identified predictors of volumetric response at the last follow-up MRI. Tumor volumetric changes were also assessed at early (3-6 months), intermediate (12-18 months), and late (>24 months) follow-up. Local control (LC) was defined as no need for additional treatment (surgical resection or repeat SRS). RESULTS: Among 261 SRS-treated VS patients, 76 (15 cystic, 61 solid) met inclusion criteria. The mean radiological follow-up was 34.0 months. After IPTW adjustment, baseline tumor volume was a significant predictor of volume reduction (p <0.01). Cystic VS demonstrated significantly greater tumor volume reduction during early and intermediate follow-up than solid VS (Mann-Whitney U: p = 0.029 and p = 0.031; IPTW-adjusted: p < 0.01 and p = 0.024, respectively). This difference was not observed at late follow-up (Mann-Whitney U: p = 0.064; IPTW-adjusted: p = 0.780). The LC rate was 100% in cystic and 98.4% in solid VS. CONCLUSION: Large cystic VS exhibit significantly greater early tumor shrinkage following SRS, with excellent local control comparable to solid VS. These findings suggest that SRS is a viable, less invasive treatment option for selected patients with large cystic VS.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.