Retreatment of vestibular schwannoma with Gamma Knife radiosurgery: clinical outcome, tumor control, and review of literature

OBJECTIVEGamma Knife radiosurgery (GKRS) has become an accepted treatment for vestibular schwannoma, with a high rate of tumor control and good clinical outcome. In a small number of cases, additional treatment is needed. This retrospective study examines the clinical outcome, reproducibility of volumetric response patterns, and tumor control rate after administering a second GKRS to treat vestibular schwannomas.METHODSA total of 38 patients were included: 28 patients underwent a radiosurgical procedure as the initial treatment (Group 1), and 10 patients underwent microsurgical resection with adjuvant radiosurgery on the tumor remnant as the initial treatment (Group 2). The indication for a second GKRS treatment was growth observed on follow-up imaging. The median margin dose was 11.0 Gy for the first procedure and 11.5 Gy for the second procedure. Tumor control after retreatment was assessed through volumetric analysis. Clinical outcome was assessed through medical chart review.RESULTSMedian tumor volume...