The Natural History of Vestibular Schwannoma Growth-prospective 40-year Data from an Unselected National Cohort

Background: Optimal management of vestibular schwannoma (VS) is still debated and thus international consensus has not been achieved. Treatment options are observation, radiotherapy, and surgery. Knowledge on the natural history of tumor growth is essential for choice of treatment modality. The aim is to present intra-/extrameatal tumor growth and management data from a prospective, unselected national cohort of patients diagnosed with VS during the period 1976-2015.

Methods: Since 1976, all data from patients diagnosed with sporadic VS in Denmark have been referred to our national treatment center, where they have been entered prospectively into the national database. Data on tumor localization, growth, and treatment were retrieved. Growth definition: >2 mm by linear measurement, in accordance with the Tokyo 2001 consensus-meeting recommendations.

Results: 3637 cases of VS were diagnosed, in which 1304 patients had surgery and 21 received radiotherapy post diagnosis. 2312 patients were observed with mean follow-up of 7.33 years. Of these, 434(19%; 102 intra-and 332 extrameatal tumors) changed to active treatment during the observation period due to tumor growth. 5 years after diagnosis, 21% of the intrameatal tumors exhibited growth during observation, whereas 37% of extrameatal tumors had grown, increasing to 25% intrameatal and 42% extrameatal after 10 years. Following growth, the intrameatal tumors were mostly observed further and the extrameatal mostly underwent surgery. Tumor growth occurred mainly within the first 5 years post diagnosis.

Conclusion: This natural history study documents the growth occurrence of both intra-and extrameatal VS during the first 12 years after diagnosis and should be used in patient counseling, management, and treatment decision making.