Grading of vestibular schwannomas and corresponding tumor volumes: Ramifications for radiosurgery

Neurosurgery, Klinik Im Park, Seestrasse 220, 8027, Zürich, Switzerland, .
Acta Neurochirurgica (Impact Factor: 1.77). 11/2012; 155(1). DOI: 10.1007/s00701-012-1553-4
Source: PubMed


Patients with vestibular schwannomas (VS) are either assigned to watchful waiting, microsurgical resection, or radiosurgery. Decision making on how to proceed is based on parameters such as age, tumor growth, loss of hearing, and the tumor's Koos grading.

In order to correlate Koos grading with tumor volume, patient records of 235 patients with VS who underwent Gamma Knife radiosurgery (GKRS) were retrospectively reviewed.

From 1994 to 2009, 235 consecutive patients underwent GKRS for sporadic VS at the Zurich Gamma Knife Center. Median follow up was 62.8 ± 33.0 months. Of the 235 tumors, 32 (13.6 %) were graded Koos I with a volume of 0.25 ± 0.3 cc; 71 (30.2 %) were graded Koos II with a volume of 0.57 ± 0.54 cc; 70 (29.8 %) were graded Koos III with a volume of 1.82 ± 1.88 cc; and 62 (26.4 %) were graded Koos IV with a volume of 4.17 ± 2.75 cc. Tumor progression was defined as a volume increase > 20 % at 2 years or later following GKRS. Overall tumor progression occurred in 21/235 (8.9 %) patients at 3.4 ± 0.9 years. Tumor progression did not differ statistically significantly in the various Koos grades: 1/32 (3.1 %) patients with VS Koos Grade I, 7/71 (9.8 %) patients with VS Koos Grade II, 6/70 (8.6 %) patients with VS Koos Grade III, and 7/62 (11.3 %) patients with VS Koos Grade IV.

To our knowledge, this is the first work correlating the various Koos grades of VS to their respective tumor volumes. In our patients, tumor volumes of VS Koos Grade IV were limited because all of our patients were eligible for radiosurgery. In our series, the outcome following GKRS for patients with VS Koos Grade IV tumors did not differ from patients with VS Koos Grades I-III. We therefore suggest to limit Koos Grade IV VS to tumor volumes < 6 cc that may be eligible for radiosurgery, and introduce an additional VS Grade V for large VS with tumor volumes of > 6 cc that may not be eligible for radiosurgery.

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    ABSTRACT: Gamma knife radiosurgery (GKRS) has for the last decades been an established treatment option for patients with small- or medium-sized vestibular schwannomas (VS), although little data is reported on long-term outcome regarding quality of life (QOL) and tumour control in this patient category. The objective of this study was to investigate long-term QOL and tumour control in GKRS-treated VS patients at our institution. Data was reviewed from a consecutive cohort of 128 patients, 62 men and 66 women, diagnosed with VS and treated with GKRS at Karolinska University Hospital between 1997 and 2003. Patients previously treated for VS, patients from abroad, and patients with neurofibromatosis were excluded from the study. Median age at the time of treatment was 66 years (range 23-89), with a median follow-up time of 104 months (range 11-165) and radiological median follow-up of 86 months (range 5-170). Five patients were lost to follow-up. Data on QOL (EQ-5D score) was obtained in 90 % (98/109) of all cases at the end of follow-up, showing low morbidity and a high QOL with median index of 0.91 (max. score 1.0) in these patients. Tumour control was achieved in 92 % (118/128) of patients after a single GKRS treatment. Ten patients had loss of tumour control, either radiologically seen as growth progression, or due to the need for salvage treatment. Neither pre-treatment growth of the vestibular schwannoma, or a large tumour size (Koos grade 3 & 4) was correlated with a higher degree of treatment failure (p = 0.695 and p = 0.647, respectively). There was no difference in tumour control in young (<60 y/o) vs. elderly (≥60 y/o) patients (p = 0.167). We report a high QOL and low morbidity at long-term follow-up after GKRS treatment in VS patients. Furthermore, a high tumour control rate was achieved independent of tumour size, patient age or pre-treatment evidence of tumour growth.
    No preview · Article · Nov 2013 · Acta Neurochirurgica
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    ABSTRACT: Typically, vestibular schwannomas (VS) react to Gamma Knife radiosurgery (GKRS) with a transient increase of tumor volume owed to tumor swelling at about 6 months followed by a reduction of tumor volume owed to tumor shrinkage at about 18 months. It is important to distinguish this transient tumor expansion (TTE) from tumor growth. We undertook this study to see if there is a typical time interval in the follow-up of VS following GKRS, which may indicate tumor growth rather than TTE. We retrospectively reviewed the patient charts of patients who underwent GKRS for unilateral sporadic VS at the Gamma Knife Center Zurich from 1994-2009 and who were treated by J. Siegfried or one of the authors (TM). Tumor progression was defined as an increase of tumor volume of ≥ 20 % as compared to the initial tumor volume at the earliest 2 years following GKRS. This time interval of ≥ 2 years was chosen in order to distinguish TTE from genuine tumor progression. Whenever tumor enlargement was suspected on follow-up MRI at ≥ 2 years following GKRS, tumor volumes were measured using custom software. From 1994-2009, 235 patients underwent GKRS in Zurich for unilateral sporadic VS. Tumor progression with a volume increase of ≥ 20 % occurred in 21/235 (8.9 %) patients at 3.4 ± 0.9 years following GKRS. Seventeen out of 235 (7 %) patients had a clinically relevant tumor progression requiring microsurgery or repeat radiosurgery. According to our data, time may be a good parameter distinguishing tumor progression due to tumor growth from TTE due to tumor swelling in VS following GKRS. Tumor growth seems to occur at about 3-4 years following GKRS for VS as opposed to TTE, which seems to be present at about 6-18 months following GKRS for VS.
    Full-text · Article · Mar 2014 · Acta Neurochirurgica
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    ABSTRACT: Background: Gamma Knife radiosurgery (GKRS) is commonly used in treating small vestibular schwannomas; however, its use for larger vestibular schwannomas is still controversial. Objective: To assess the long-term safety and efficacy of treating eligible Koos grade 4 vestibular schwannomas with GKRS. Methods: We conducted a single-center, retrospective evaluation of patient undergoing GKRS for Koos grade 4 vestibular schwannomas. We evaluated clinical, imaging, and treatment characteristics and assessed treatment outcome. Inclusion criteria were tumor size of ≥4 cm and follow-up of at least 6 months. Patients with neurofibromatosis type 2 were excluded. Primary outcomes measured were tumor control rate, hearing and facial function preservation rate, and complications. All possible factors were analyzed to assess clinical significance. Results: Sixty-eight patients met inclusion criteria. Median follow-up was 47 months (range, 6-125 months). Baseline hearing was serviceable in 60%. Median tumor volume at radiosurgery was 7.4 cm (range, 4-19 cm). The median marginal dose used was 12 Gy at the 50% isodose line. Actuarial tumor control rates were 95% and 92% at 2 and 10 years, respectively. Actuarial serviceable hearing preservation rates were 89% and 49% at 2 and 5 years, respectively. Facial nerve preservation was 100%. Clinical complications included balance disturbance (11%), facial pain (10%), facial numbness (5%), and tinnitus (10%). Most complications were mild and transient. Hydrocephalus occurred in 3 patients, requiring ventriculoperitoneal shunt insertion. Larger tumor size was significantly associated with persisting symptoms post-treatment. Conclusion: Patients with Koos grade 4 vestibular schwannomas and minimal symptoms can be treated safely and effectively with GKRS. Abbreviations: GKRS, Gamma Knife radiosurgeryVS, vestibular schwannoma.
    No preview · Article · Nov 2015 · Neurosurgery