Abstract:Object. The purpose of this study was to confirm, by using a sequential volume mapping (SVM) technique, that gamma knife radiosurgery (GKS) induces negative growth in vestibular schwannomas (VS).
Methods. Over a period of 5 years, 126 small- to medium-sized (< 15 cm3) VSs were treated using microradiosurgical techniques within a standard protocol. All patient data were collected prospectively. Sequential magnetic resonance imaging was performed every 6 months to assess the volume of the tumor, based on spec… Show more
“…The incidence of this transient growth pattern has been reported to range from 3% to 80% [5,8,9,16,25,[29][30][31][32][33][34], and one reason for this disparity is thought to be the method for evaluating enlargement. It is necessary to determine whether tumors that enlarge early after treatment will continue to grow or instead begin to shrink.…”
Section: Tumor Volume Change Patterns and Peaks In Transient Tumor Vomentioning
“…The incidence of this transient growth pattern has been reported to range from 3% to 80% [5,8,9,16,25,[29][30][31][32][33][34], and one reason for this disparity is thought to be the method for evaluating enlargement. It is necessary to determine whether tumors that enlarge early after treatment will continue to grow or instead begin to shrink.…”
Section: Tumor Volume Change Patterns and Peaks In Transient Tumor Vomentioning
“…Results of the first GKS treatment for VS were evaluated after almost 3 years (3,16,40). On each follow-up MRI scan, the tumor volume was calculated from 6 length measurements, defined precisely by anatomic landmarks.…”
This is the first report to address repeat GKS for vestibular schwannomas. After long-term follow-up, repeat GKS with a low marginal dose seems to be a safe and effective treatment in selected patients harboring regrowth of small vestibular schwannomas that have previously been treated with GKS.
“…To our knowledge, authors of cohort studies have not used volumetric assessment in determining the radiosurgical response, and thus our data may prove useful. 27 …”
Volume measurement on 3D-SPGR MR imaging was a suitable method to assess tumor changes. Volume changes beyond twofold or continuous enlargement for longer than 2 years after radiosurgery are key criteria in rating the effects of radiation. Some cases of hydrocephalus after radiosurgery resolved spontaneously and their rates of occurrence were similar to the typical incidence of hydrocephalus associated with VS.
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