Age-Based Variation in Treatment Modality and Trends from 2004 to 2021 for Vestibular Schwannoma

Introduction: Vestibular schwannomas (VS) are benign tumors arising from the vestibulocochlear nerve, managed with surgical resection, stereotactic radiosurgery (SRS), fractionated radiotherapy, and increasingly, observation. Patient and tumor characteristics drive selection of intervention versus observation. This analysis explores the evolution of the impact of tumor size and age on management over the last 20 years.

Methods: Using the national Surveillance, Epidemiology and End Results (SEER) database, this retrospective analysis collated demographic, clinical, and treatment data on 23,488 VS cases from 2004 to 2021. An ANOVA was used to analyze differences in means for continuous data while chi-square and Cramer’s V were used to calculate effect size phi for categorical data after the cohort was divided into age groups of <65 years, 65 to 80 years, and >80 years of age.

Results: The surgery group was significantly younger than the observation group (49.8 ± 0.15 vs. 60.4 ± 0.15 years). Surgery was the preferred treatment modality for <65 years while observation was the majority in the 65- to 80-year (60.1%) and >80 years (75.5%) cohorts ([Fig. 1]). Radiation overall (encompassing both fractionated radiotherapy and radiosurgery) was similar between age cohorts. Diagnosis year was associated with treatment choice across age groups (p < 0.001). Observation increased significantly with corresponding decreases in radiation/surgery ([Fig. 2]). Between the 2004 and 2008 and 2019 and 2021 cohorts, observation in patients <65 increased 19.8% while surgery decreased 10.9% ([Fig. 2]).

As tumor size was taken into account, surgery was the preferred modality for >2 cm VS and remained stable in the 2- to 4-cm and >4-cm cohorts at the relative age group ([Fig. 3]). Across all sizes, observation increased in frequency with age while surgery decreased with age. The strongest impact of age on treatment was observed in the group with tumors 2 to 4 cm (phi = 0.237). The largest effect for time on treatment modality phi = 0.121 was found in tumors <2 cm in patients <65 ([Fig. 4]). Overall, there was a decrease in radiation and surgery with an increase in observation, especially for the <65-year cohort ([Fig. 4]). For patients 65 to 80 years, treatment of tumors <2 cm and 2 to 4 cm shifted significantly over time (p < 0.001), but those >4 cm did not experience a significant change (p = 0.067).

Discussion: Analysis of treatment type grouped by age and tumor size at diagnosis revealed drastic differences in rates of observation and surgery. The strongest impact of age on treatment was observed in tumors 2 to 4 cm. In these cases, the threshold for intervention in a younger population, often with fewer medical comorbidities will be lower, favoring intervention. Changes in treatment modality over time for patients <65 are most pronounced in tumors <2 cm. Overall, observation continued to increase as initial management across tumor size and age groups, further bolstered by increased detection of incidental asymptomatic VS. Further studies are needed to elucidate potential etiologies for this trend.