Long-term natural history and patterns of sporadic vestibular schwannoma growth: A multi-institutional volumetric analysis of 952 patients

Abstract

Background: The current study aims to characterize the natural history of sporadic vestibular schwannoma volumetric tumor growth, including long-term growth patterns following initial detection of growth.

Methods: Volumetric tumor measurements from 3505 serial MRI studies were analyzed from unselected consecutive patients undergoing wait-and-scan management at three tertiary referral centers between 1998 and 2018. Volumetric tumor growth was defined as a change in volume ≥20%.

Results: Among 952 patients undergoing observation, 622 experienced tumor growth with initial growth-free survival rates (95% CI) at 1, 3, and 5 years following diagnosis of 66% (63-69), 30% (27-34), and 20% (17-24). Among 405 patients who continued to be observed despite demonstrating initial growth, 210 experienced subsequent tumor growth with subsequent growth-free survival rates at 1, 3, and 5 years following initial growth of 77% (72-81), 37% (31-43), and 24% (18-31). Larger tumor volume at initial growth (HR 1.13, P = .02) and increasing tumor growth rate (HR 1.31; P < .001) were significantly associated with an increased likelihood of subsequent growth, whereas a longer duration of time between diagnosis and detection of initial growth was protective (HR 0.69; P < .001).

Conclusions: While most vestibular schwannomas exhibit an overall propensity for volumetric growth following diagnosis, prior tumor growth does not perfectly predict future growth. Tumors can subsequently grow faster, slower, or demonstrate quiescence and stability. Larger tumor size and increasing tumor growth rate portend a higher likelihood of continued growth. These findings can inform timing of intervention: whether upfront at initial diagnosis, after detection of initial growth, or only after continued growth is observed.

Keywords: acoustic neuroma; growth; natural history; observation; wait-and-scan.

Fig. 1

Kaplan-Meier curves demonstrating (A) initial growth-free survival rates following diagnosis; (B) subsequent growth-free survival rates following detection of initial growth; (C) subsequent growth-free survival rates for tumors that grew <50% or ≥50% in volume per year from diagnosis to initial growth; (D) subsequent-subsequent growth-free survival rates (i.e., three total documented episodes of growth); and, (E) overlaid initial, subsequent, and subsequent-subsequent growth-free survival rates.

Fig. 2

Spaghetti (or line) plots characterizing the evolution in tumor volume following diagnosis from representative tumors among (A) the subgroup that demonstrated accelerated subsequent growth following initial growth; (B) the subgroup that demonstrated subsequent growth but at a slower rate than the rate to initial growth; and, (C) the subgroup that entered a period of quiescence with stability in tumor volume following initial growth.