Rates and Predictors of Follow-Up Loss after Radiosurgery for Sporadic Vestibular Schwannomas

Introduction: Stereotactic radiosurgery (SRS) is a cornerstone of vestibular schwannoma (VS) treatment with tumor control rates of over 90% on long-term follow-up. After treatment, however, patients must be followed up with serial imaging to assess for progression. This study evaluated patient adherence to imaging surveillance after SRS for VS.

Materials and Methods: Patients from 2005 to 2017 with sporadic VS treated initially with SRS were included, clinical data were retrospectively reviewed, and the U.S. Census Bureau was queried for demographic data based on patients’ zip codes. Outcomes of interest included (1) follow-up loss unrelated to death and prior to any salvage therapy and (2) inconsistent adherence to surveillance recommendations during the period of active follow-up. Follow-up loss was defined as patients who did not ever return for an MRI 2 years beyond the recommended time period. Inconsistent imaging follow-up was defined as failure to undergo an MRI within 1 year of a recommended timeframe during the available follow-up period for review.

Results: The cohort consisted of 303 patients (female: 153, male: 150) with a median tumor volume of 0.85 cm³ (range: 0.7–15) who underwent a median margin and maximum dose of 12.5 Gy (range: 11–14) and 25 Gy (range: 20.8–30), respectively. Median follow-up duration for the cohort was 94.7 months (range: 0–204.5), and censoring events for the cohort included death (n = 38, 12.7%), salvage treatment (n = 26, 8.7%), and last imaging follow-up (n = 235, 78.6%). Overall, 95 patients (31.8%) were lost to follow-up with a median follow-up duration of 58.5 months (range: 0–169.8) prior to this occurring. Of these patients, 5 (1.7%) had no follow-up after SRS, and 18 (5.9%) had less than 2 years of follow-up. Additionally, 76 (25.4%) patients demonstrated inconsistent imaging adherence during a period of follow-up. Estimated 1-, 5-, and 10-year follow-up loss rates were 3.8% (95% CI: 3.1–4.6%), 17.4% (95% CI: 14.4–20.9%), and 31.8% (95% CI: 26.8–37.3%), respectively. A multivariable Cox proportional hazards analysis identified larger tumor volume (HR: 1.1, 95% CI: 1.002–1.2, p = 0.027) and a history of myocardial infarction or coronary artery disease requiring intervention (HR: 2.1, 95% CI: 1.3–3.6, p = 0.005) to be associated with time to follow-up loss. In a multivariable nominal logistic regression analysis, patients who were employed or active students (OR: 2.4, 95% CI: 1.1–4.9, p = 0.02), patients who came from zip codes associated with smaller populations (unit OR by 1,000 people: 0.98, 95% CI: 0.96–0.99, p = 0.02), and had longer follow-up (unit OR by year: 1.2, 95% CI: 1.1–1.3, p < 0.0001) were at increased risk of inconsistent adherence to imaging follow-up.

Conclusion: Follow-up loss and adherence to recommended surveillance imaging timeframes after SRS for VS remains a challenge. Significant medical history and patient sociodemographic factors may influence the risk of follow-up loss and inconsistent imaging adherence.

Publication History

Article published online:
07 February 2025