The target population of the benefit assessment is patients with vestibular schwannoma requiring intervention (primary, recurrence, or residual tissue after partial resection). The experimental intervention is single-session stereotactic radiosurgery (SRS) using linear accelerators or cobalt-60 gamma sources. The comparator intervention is microsurgical resection.

The investigation examined the following patient-relevant outcomes:

• Mortality
• Morbidity (particularly dizziness, hearing ability, facial paresis, and other neurological symptoms)
• Health-related quality of life
• Adverse events
• Length of hospital stay

Randomized controlled trials (RCTs) were to be primarily included in the benefit assessment. Where no RCTs were available, non-randomized, prospective, comparative studies were to be included, e.g. quasi-randomized controlled studies, non-randomized controlled studies with active allocation of the intervention following a preplanned rule, or prospective comparative cohort studies with passive allocation of the intervention. There were no restrictions regarding the study duration.

The systematic search for studies was conducted in the databases MEDLINE, Embase, and Cochrane Central Register of Controlled Trials. In parallel, a search for relevant systematic reviews was conducted in the databases MEDLINE, Embase, Cochrane Database of Systematic Reviews, and HTA Database.

The following sources of information and search techniques were additionally used: trial registries, manufacturer queries, documents sent by the Federal Joint Committee (Gemeinsamer Bundesausschuss, G-BA), viewing of reference lists, documents made available from hearing procedures, and author queries.

Relevant studies were selected by 2 persons independently from one another. Any discrepancies were resolved by discussion between them. Data were extracted into standardized tables. To assess the qualitative certainty of results, study-level criteria for the risk of bias were assessed, and the risk of bias was rated as high or low in each case. The results of the individual studies were organized according to outcomes and described.

In addition to the comparison of the individual studies’ results, metaanalyses and sensitivity analyses were conducted and effect modifiers investigated, provided that the methodological prerequisites had been met.

For each outcome, a conclusion was drawn on the evidence for (greater) benefit and (greater) harm, with 4 levels of certainty of conclusions: proof (highest certainty of conclusions), indication (moderate certainty of conclusions), hint (lowest certainty of conclusions), or neither of the above 3. The latter is the case if no data are available or the available data do not permit classification into one of the 3 other categories. In that case, the conclusion “There is no hint of (greater) benefit or (greater) harm” was drawn.

Subsequently, an assessment of benefit and harm was carried out across outcomes.