Vestibular schwannoma: natural growth and possible predictive factors.

Background: Prediction of vestibular schwannoma (VS) growth would allow for a more differentiated follow-up protocol. Objectives: The natural course of a VS and predictive factors of growth are investigated. Methods: Sixty-two sporadic VS cases diagnosed between 2003 and 2015 were included in this retrospective cohort study. After initial surveillance, active therapy was initiated in 31/62 patients. Regular magnetic resonance images (MRIs) were performed. Two mm/year linear difference was the cut-off value for significant growth. The STROBE guidelines have been implemented. Results: Growth of the tumor was detected in 56% of patients and mainly observed in the first three years of follow-up. Tumor size remained stable in 34% and decreased in 10% of patients. No baseline information, symptom, or sign was found to be predictive for growth. Conclusions: In 56% of the initially conservatively managed VSs growth was observed and active treatment was initiated. Eighty-seven percent of the growing VSs were identified during the first three years of follow-up. The initially larger VSs seemed to grow faster and needed active treatment earlier during follow-up. No predicting factors for growth identified from the literature could be confirmed in the present study. Serial MRI remains the appropriate method to detect tumor growth.