Outcomes of Gamma Knife Surgery retreatment for growing vestibular schwannoma and review of the literature.

[OBJECTIVE] Gamma Knife surgery has become an accepted treatment for small to medium‑size vestibular schwannoma with a high rate of tumor control and good clinical outcome. When GKS treatment fails to stop tumor growth, GKS retreatment can be proposed in selected cases. This retrospective study examines the clinical and tumor control outcome after the second GKS retreatment for the same vestibular schwannomas.

[METHODS] A total of 14 consecutive vestibular schwannomas patients retreated with 2nd GKS were included: The median time interval between GKS treatments was 44 months, and the median follow‑up duration after last GKS retreatment was 60 months. The median marginal dose used for the first and second treatments was 12 Gy. The median tumor volume at the initial GKS was 2.4cc (range 0.27-3.8) and was 3.8cc (range 1.21-7.6) at the GKS retreatment.

[RESULTS] At the last follow‑up, 93% (13 patients) had tumor growth control, decreased in 4, remained unchanged in 9, and increased tumor size in one patient. New facial or severe trigeminal palsy did not occur after the second GKS retreatment. The hearing was not preserved except in one patient post-GKS retreatment.

[CONCLUSIONS] GKS retreatment after the failure of initial GKS to control vestibular schwannomas growth appears to be an effective strategy and can be proposed as an alternative to microsurgery when the tumor volume remains within the usual radiosurgical range.