Gillian A. Whitfield

Objective: There is a need for a definitive RCT comparing upfront stereotactic radiosurgery (SRS) versus watch-and-wait (WW) for long-term hearing preservation in vestibular schwannoma (VS). Specific objectives of this feasibility study were to: (1) assess patient eligibility and recruitment/ retention rates, (2) determine completion rates/ times, and (3) estimate the variance in key proposed outcome measures to inform sample-size estimation for an RCT. Study design: Nonrandomized, single-centre, prospective study. Setting: Tertiary-referral centre. Patients: Thirty-one patients with sporadic VS undergoing WW (n = 22) or SRS (n = 9). Intervention(s): Four-frequency average pure-tone audiometry (4FAPTA) thresholds, Word Recognition Scores (WRS), monaural/antiphasic Digits-in-Noise speech reception thresholds (DiN SRT ₅₀ ), and self-reported outcomes including the Speech, Spatial and Qualities of Hearing Scale (SSQ) and Tinnitus Functional Index (TFI). Main outcome measures: Feasibility metrics (recruitment, completion rates, testing times). Variance of outcome measures (hearing-related: 4FAPTA, monoaural/ antiphasic DiN-SRT ₅₀ , WRS. Patient-reported outcomes: SSQ, TFI. Results: Forty-four patients were recruited over 7 months. Thirty-one (70.5%) met inclusion criteria, and 25 (80%) completed all tests. Average time to complete the assessments was 1 hour 42 minutes. Mean 4FAPTA (±SD) in VS-affected ears was 42 ± 14 dB HL (WW) and 55 ± 9.4 dB HL (SRS). Antiphasic DiN-SRT _{50 thresholds} were WW: -14.2 dB SNR ± 4.1; SRS: -11.6 dB SNR ± 1.9, and 4FAPTA and antiphasic DiN-SRT ₅₀ were correlated ( P < 0.001) in VS-affected ears. Conclusions: This study has demonstrated sufficient eligibility and recruitment/retention rates for the proposed RCT and high-test completion rates with acceptable duration. Variability estimates of key outcome measures (DiN-SRT _50, 4FAPTA) have also been provided to determine the sample size for the RCT.

Skull base chordomas and chondrosarcomas are distinct types of rare, locally aggressive mesenchymal tumors that share key principles of imaging investigation and multidisciplinary care. Maximal safe surgical resection is the treatment choice for each, often via an expanded endoscopic endonasal approach, with or without multilayer skull base repair. Postoperative adjuvant radiation therapy is frequently administered, usually with particle therapy such as proton beam therapy (PBT). Compared with photon therapy, PBT enables dose escalation while limiting damage to dose-limiting neurologic structures, particularly the brainstem and optic apparatus, due to energy deposition being delivered at a high maximum with a rapid decrease at the end of the penetration range (Bragg peak phenomenon). Essential requirements for PBT following gross total or maximal safe resection are tissue diagnosis, minimal residual tumor after resection, and adequate clearance from PBT dose-limiting structures. The radiologist should understand surgical approaches and surgical techniques, including multilayer skull base repair, and be aware of evolution of postsurgical imaging appearances over time. Accurate radiologic review of all relevant preoperative imaging examinations and of intraoperative and postoperative MRI examinations plays a key role in management. The radiology report should reflect what the skull base surgeon and radiation oncologist need to know, including distance between the tumor and PBT dose-limiting structures, tumor sites that may be difficult to access via the endoscopic endonasal route, the relationship between intradural tumor and neurovascular structures, and tumor sites with implications for postresection stability. ^©RSNA, 2024 Supplemental material is available for this article.