title: Long-term follow-up results of linear accelerator-based radiosurgery for vestibular schwannoma using serial three-dimensional spoiled gradient-echo MRI.
abstract: We examined the characteristic changes in vestibular schwannoma (VS) volume after treatment with linear accelerator-based radiosurgery (LBRS) and the long-term therapeutic effects, by performing three-dimensional (3D) MRI evaluations of tumor volumes. We included 44 patients in whom tumor volume changes could be observed using 3D-spoiled gradient-echo MRI for at least 5 years. Examinations were performed every 3-4 months for the first 2 years after treatment and every 6-12 months thereafter. Enlargement or shrinkage was determined as a change of at least 20% from the volume at the time of treatment. The median observation period was 13.8 years (range, 5.5-19.5 years). The tumor control rates at 5 and 10 years after treatment and at the final MRI were 90.9%, 90.0%, and 88.6%, respectively. Tumor volume changes were categorized into the following four patterns: enlargement, five patients (11.4%); stable, three patients (6.8%); transient enlargement, 24 patients (54.5%); and direct shrinkage, 12 patients (27.3%). Bimodal peaks were observed in three of the 24 patients with transient enlargement. Tumor volume changes from 5 and 10 years post-LBRS to the final observation point were observed in 27 (64.2%) and 10 patients (33.3%), respectively. The long-term tumor volume changes observed after LBRS suggest that radiation exerts long-term effects on tumors. Furthermore, while transient enlargements in tumor volume were characteristic, true tumor enlargements should be characterized by increased volumes of more than two-fold and continued growth for at least 2 years.
authors.affiliation: Departments of Neurosurgery and Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan. Electronic address: takayuki@nagasaki-u.ac.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsuo
authors.affiliation: Departments of Neurosurgery and Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Okunaga
authors.affiliation: Departments of Neurosurgery and Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Kensaku
authors.initials: K
authors.lastname: Kamada
authors.affiliation: Departments of Neurosurgery and Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Izumo
authors.affiliation: Departments of Neurosurgery and Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Hayashi
authors.affiliation: Departments of Neurosurgery and Radiology, Nagasaki University School of Medicine, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
authors.forename: Izumi
authors.initials: I
authors.lastname: Nagata
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000473:pathology* / Q000601:surgery*; D010315:Particle Accelerators; D016634:Radiosurgery / Q000379:methods*; D047368:Tumor Burden
keywords: 3D volume measurements; Linac-based radiosurgery; Long-term follow-up; Vestibular schwannoma