ANS027 - Spontaneous Volumetric Tumor Regression During Wait-and-Scan Management of 952 Sporadic Vestibular Schwannomas
Sunday, May 1, 2022
9:06 AM – 9:13 AM CT
Location: Landmark A
John P. Marinelli, MD
Daniel E. Killeen, MD
Zane Schnurman, MD
Jacob B. Hunter, MD
Christine M. Lohse, MS
Douglas Kondziolka, MD, MSc
Matthew L. Carlson, MD
Objective: Spontaneous tumor shrinkage during wait-and-scan management of sporadic vestibular schwannoma is generally considered an uncommon phenomenon. However, most data informing this understanding stem from singleslice linear tumor measurements taken in the axial imaging plane. The objective of current work was to characterize the regression capacity of sporadic vestibular schwannomas using volumetric tumor measurements.
Study Design: Retrospective cohort study using slice-by-slice, three-dimensional volumetric tumor measurements on serial MRI studies.
Setting: Three tertiary referral centers.
Patients: Patients with sporadic vestibular schwannoma.
Interventions: Wait-and-scan.
Main Outcome Measures: Regression-free survival rates where regression is defined by a decrease of ≥20% of thetumor volume.
Results: Among 952 patients undergoing observation, 123 experienced volumetric tumor regression following diagnosis at a median of 1.2 years (IQR 0.6-2.9). Volumetric regression-free survival rates (95% CI; number still at-risk) at 1, 3, and 5 years following diagnosis were 94% (92-95; 662), 86% (83-89; 275), and 78% (73-82; 132), respectively. Neither age at diagnosis (HR 1.05; p=0.54) nor volume at diagnosis (HR 0.94; p=0.31) was significantly associated with tumor regression. Among 405 patients who demonstrated an initial period of tumor growth but continued wait-and-scan management, 48 experienced subsequent volumetric regression at a median of 1.2 years (IQR 0.8-2.6) following initial growth. Subsequent volumetric regression-free survival rates at 1, 3, and 5 years following initial growth were 94% (92-97; 260), 84% (79-89; 99), and 75% (67-83; 43), respectively.
Conclusions: Spontaneous regression in volumetric tumor size during wait-and-scan management occurs more frequently than suggested by prior studies using linear tumor measurements and can even occur following previous episodes of documented tumor growth.
Professional Practice Gap & Educational Need: Current understanding of the natural history of sporadic vestibular schwannoma growth during observation is predominantly informed by studies employing single-slice linear tumor measurements in the axial imaging plane. The current study examines the natural history of sporadic vestibular schwannoma in a large cohort of patients at three tertiary referral centers across the United States using sensitive sliceby- slice volumetric measurements, showing that more tumors exhibit periods of shrinkage than previously reported.
Learning Objective: Describe the capacity for sporadic vestibular schwannomas to undergo periods of tumor shrinkage following diagnosis, as well as following periods of previously documented growth in patients who elected continued observation.
Desired Result: When considering definitive treatment of sporadic vestibular schwannoma during wait-and-scan management, practitioners would account for the potential that not all tumors that exhibit growth continue to grow, and tumors can regress in size during continued observation following previous episodes of documented growth.
Level of Evidence: III
Indicate IRB or IACUC: IRB approval was obtaining from each participating center prior to data collection (IRB numbers,15-008224, 112016-040, and S13-00063, respectively).