Carlson, Matthew L.

Objective: To survey critical areas of variation in published research methodology with a primary aim of highlighting fundamental aspects that contribute to ongoing controversy surrounding optimal management of patients with sporadic vestibular schwannoma. Interventions: Observation, stereotactic radiosurgery (SRS), and microsurgery. Main outcome measures: Variation in reported outcomes surrounding facial function, useful hearing, tumor pseudoprogression following SRS, and tumor growth/natural history. Results: Published research defines “good” post-treatment facial function as anything ranging from HB I, ≤HB II, to ≤HB III. While most studies define serviceable hearing as AAO Class A/B, others include Class C in published post-treatment hearing preservation results; meanwhile, patients report their greatest decrement in quality-of-life at a threshold around 75% in word recognition scores. Heterogeneously defined as post-SRS tumor growth 6 months after SRS to 5 years after SRS, the reported incidence of tumor pseudoprogression ranges from 7% to 77% within the published literature. Natural history studies that employ linear tumor measurements consistently suggest most tumors do not grow following diagnosis, whereas volumetric studies of natural history suggest the exact opposite is true. Limited follow-up and absent time-to-event analyses undermine many outcomes surrounding vestibular schwannoma that are inherently time-dependent. Conclusions: Disparate definitions used in vestibular schwannoma research beget variable outcome reporting and confuse interpretation of optimal management, particularly for the increasingly common scenario of a small tumor in a minimally symptomatic patient. Progress towards optimizing management requires re-evaluation and alignment on key outcome measures to improve consistency in reporting with renewed emphasis on clinically significant, patient-driven outcomes that often exceed the thresholds most frequently studied to date.