Hypofractionated Versus Single-Session Radiosurgery to Preserve Hearing in Patients Affected by Sporadic Vestibular Schwannoma: The ACOUNEU Randomized Clinical Trial.

Purpose: During the last decades, in addition to tumor control, hearing preservation has become an important priority in the treatment of vestibular schwannoma (VS). Given that the potential advantages of hypofractionated radiosurgery (hRS) over single-session radiosurgery (RS) in terms of improved hearing outcomes remain unclear, this randomized trial aims to provide a robust answer to this question.

Methods and materials: The present is a double-arm randomized clinical trial. The study started in 2011 and the last patient was enrolled in 2020. The minimum follow-up was 36 months. The trial involved patients with a diagnosis of sporadic VS with preserved hearing. One hundred and eight patients were enrolled. Participants were randomized to receive either hRS (18 Gy/3 consecutive fractions) or RS (most commonly 12 Gy/1 fraction). At each follow-up, clinical assessment, volumetric magnetic resonance imaging, and audiometry were evaluated. The primary endpoint was hearing sparing 36 months after RS or hRS. The maintenance of a serviceable hearing was defined according to the American Academy of Otorhinolaryngology Head and Neck Surgery classification.

Results: Of the 108 randomized patients, 100 (47 RS and 53 hRS) were included in the analysis (mean age, 55 years; 56% female). No significant differences between hRS and RS were found in terms of hearing preservation (hazard ratio, 1.083; [95% CI, 0.603-1.946], and P = .789), with pretreatment hearing status, age, and dose to cochlea being the only significant predictors. No other parameters, including tumor volume, were associated with hearing preservation. At a median follow-up of 62 months, local control was 92% (95% CI, 84.8%-96.5%). Treatment-related toxicity was mild or moderate, in general not exceeding National Cancer Institute Common Terminology Criteria for Adverse Events grade 2.

Conclusions: To our knowledge, this is the first randomized clinical trial comparing 2 different radiosurgical regimens while focusing on hearing preservation. The study failed to demonstrate the potential advantages of hRS over RS with respect to hearing preservation. The volumetric analysis confirmed an excellent postradiosurgery tumor control rate for both RS and hRS groups. These results may guide the clinicians in the treatment schedule choice to preserve hearing in patients with VS.