Clinical and Imaging Response to Trigeminal Schwannoma Radiosurgery: A Retrospective Analysis of a 28-Year Experience

Abstract

Objective The purpose of this study was to evaluate long-term clinical outcomes and tumor control after stereotactic radiosurgery (SRS) for trigeminal schwannoma (TS). Methods During a 28-year period (1989–2017), 50 patients underwent SRS for TS. The median patient age was 51 years (range: 15–87 years). A total of 17 patients had a previous tumor resection: 10 had a single procedure, 5 had two procedures, and 2 had three procedures. The median and mean times between tumor resection and SRS were 12 and 24 months (range: 1–90 months), respectively. Four patients had neurofibromatosis II (NF2). Based on location, tumors were classified as root type (7), ganglion type (22), or dumbbell type (21). The median radiosurgery target volume was 3.4 cm3 (range: 0.10–18 cm3), median target dose was 14 Gy (range: 12–20 Gy), and the median number of isocenters was 6 (range: 1–15). The median and mean times to last follow-up was 36.9 and 55.2 months (range: 4–205 months), respectively. Eighteen patients (36%) had longer than 5-year follow-up, and seven patients (14%) had longer than 10-year follow-up. Results The tumor control rate was 92% and the clinical improvement or stabilization rate was 94%. After SRS, the rates of progression free survival (PFS) at 1, 5, and 10 years were 98, 84, and 84%, respectively. Factors associated with improved PFS were female sex (p = 0.014) and smaller tumor volume (p = 0.022). In this series, we did not find that tumor type (root, ganglion, and dumbbell) had a statistically significant correlation to PFS. Forty-seven patients had neurological signs or symptoms at presentation. At last follow-up, neurological signs or symptoms improved in 22/47 (47%), remained unchanged in 24/50 (48%), and worsened due to tumor progression in 3/50 (6%). One patient (2%) developed temporary symptomatic adverse radiation effect (ARE) and three additional patients (6%) had transient imaging evidence of peritumoral reactive edema but no new symptoms. Conclusion As a single outpatient procedure, SRS was associated with long-term freedom from additional management in 84% of patients. Nearly half the treated patients experienced improvement in neurological symptoms or signs.

Trigeminal Schwannoma: A Retrospective Analysis of Endoscopic Endonasal Management, Treatment Outcomes, and Neuropathic Sequelae

“…In comparison, the GKRS experience at UPMC for TS has been previously described with 50 patients from 1989 to 2017, 17 of which underwent prior surgery. 18…”

“…In comparison, the GKRS experience at UPMC for TS has been previously described with 50 patients from 1989 to 2017, 17 of which underwent prior surgery. 18 EEA for TS offers unique advantages compared with open lateral cranial base approaches as it obviates the need for temporal lobe exposure or retraction, avoids unnecessary manipulation of adjacent cranial nerves, and provides a direct corridor for tumor ablation via the transpterygoid approach AE anterior maxillotomy. This is increasingly evident when the pattern of iatrogenic cranial nerve dysfunc-tion for lateral skull base approaches is examined; Samii 2 (8.3%, facial nerve), Al-Mefty 19 (8.0%, abducens nerve and 3.7%, trochlear nerve), Goel 16 (4.1%, abducens nerve, 2.7%, trochlear nerve, facial nerve, 2.7%, and vestibulocochlear nerve, 2.7%), and Wanibuchi 20 (oculomotor nerve, 1.9%) describe a variety of cranial nerve deficits following TS resection with a major complication rate ranging from 1.4 to 33% and a mortality rate of 2.7%.…”

“…By comparison, the GKRS experience at UPMC demonstrates the rate of improvement for pain syndrome following treatment at roughly 44%. 18 Concerning degree of resection, 75% of patients achieved either a gross total (50%) or near-total resection (25%) via EEA. EEA is one of many tools that should be considered in the multimodality treatment paradigm of TS.…”

“…It is clear that to better understand the intricate complexities of the trigeminal nerve and its dysfunction, future studies will require prospective classification of these key details with established trigeminal nerve parameters. In an attempt to address this deficiency, previously described preoperative trigeminal nerve nomenclature by Niranjan and colleagues 18 was employed in this comprehensive analysis of surgical outcomes. Postoperative classification remains even more difficult to categorize given acute pain versus chronic pain as well as multimodality treatments that could potentially be employed to address clinical symptoms.…”

Clinical and Imaging Outcomes After Trigeminal Schwannoma Radiosurgery: Results From a Multicenter, International Cohort Study

“…Gamma knife ® (Elekta AB) SRS techniques have been previously described in detail. 25 Radiosurgery was performed in a multidisciplinary fashion with a neurosurgeon, radiation oncologist, and medical physicist. Dose and target selection were at the discretion of the treatment team and were based in part on any prior surgical or radiation treatment if performed, target volume, neurological symptoms and signs, and adjacent structures considered at risk (such as the optic apparatus or brainstem).…”