A De-escalated MRI Surveillance Protocol for Intracanalicular Vestibular Schwannomas in the Elderly

Introduction: Current consensus recommends MRI surveillance for vestibular schwannoma (VS) under observation with an initial scan at 6 months after diagnosis, followed by annual imaging for 3–5 yrs, and then biennial through 10 yrs. However, this protocol does not account for age, tumor size or location, and may result in MRI overutilization in the elderly with intracanalicular VS. The current study evaluates the safety and efficacy of a de-escalated MRI surveillance protocol in this cohort.

Methods: A retrospective review was performed at a tertiary referral center from 2003 to 2021 of patients with sporadic intracanalicular VS, ≥ 70 yrs old at time of diagnosis with ≥ 3 yrs of MRI surveillance. A simulated de-escalated MRI surveillance protocol (0.5, 1.5, 3.5 and 5.5 yrs since diagnosis) was performed using linear regression. Main outcome measures were linear VS growth (≥2 mm increase compared to initial MRI), extension to cerebellopontine angle (CPA) and VS interventions (radiosurgery/surgery).

Results: 53 patients were identified (mean initial size 5.5mm; range: 1.5-22) at a mean age of 74.9 ± 4.4 yrs, surveilled for a mean of 6.7 ± 3.4 yrs. 51% demonstrated growth (mean total growth 4.8 ± 2.8mm) with mean first growth detected at 3.2 yrs (range: 0.4-10.2). 8% had rapid growth (≥4mm linear growth/yr), resulting in early intervention at 0.8 yrs after diagnosis. 25% developed tumor extension to the CPA but none > 10mm. 28% underwent intervention for VS growth (93% radiosurgery). There were no complications or mortalities related to VS or its interventions. On simulation of a de-escalated MRI protocol compared to conventional, the mean delay in receiving intervention was 8 mo, resulting in a predicted 1.9mm of additional growth and new CPA extension in 14%. All rapid growers were detected at the 6-mo MRI.

Conclusions: In patients ≥70 years with intracanalicular VS, a de-escalated MRI surveillance protocol did not significantly delay detection of meaningful VS growth or intervention. Given the low risk for complications and CPA growth >10mm with observation in this cohort, adopting a de-escalated MRI protocol would be safe and effective.