Stereotactic radiosurgery vs. fractionated radiotherapy for large vestibular schwannomas: should FSRT be the preferred treatment?

Introduction: To evaluate the effect of fractionation and prognostic factors on local control (LC) in the treatment of vestibular schwannoma (VS).

Methods: The medical records of 104 patients with vestibular schwannoma who were treated with stereotactic radiosurgery (SRS) from January 2015 to September 2023 were retrospectively collected. SRS was performed using Cyberknife^® robotic lineer accelerator. The primary endpoint of this study was LC rates. The chi-square test or Fischer's exact test, where appropriate, was used to compare progression rates in patients with small (< 20 cc) and large tumors (≥ 20 cc) which were treated in different fractionation schemes.

Results: The median total prescribed dose was 18 Gy (range, 12-30 Gy). With a median 54.8 month follow-up period (range, 3.4-111.9 month), 12 (12%) patients had progressive disease. Regression in tumor size, and stable disease was observed in 49 (47%) and 43 (41%) patients, respectively. The 3-y LC rate was 89% in all cohort and similar between patients who received SRS in 1, 3, and 5 fractions (p = 0.074). LC rates were slightly lower in patients with large tumors than those with small tumors (83% vs 94%, p = 0.200). Patients with large tumors (≥ 20 cc) which was treated with SRS in 1 fraction had a higher rate of progression compared to patients with small tumors (< 20 cc) (100% vs 0%, p = 0.006). But there was no difference between progression rates in large and small tumors, which were treated in 3, and 5 fractions (p = 0.100 and p = 1.000, respectively). No prognostic factors were found to predict tumor progression.

Conclusion: Both SRS and fractionated stereotactic radiotherapy (FSRT) provides high LC in patients with VS, however, FSRT may be preferred for large tumors due to higher LC rates compared to single fraction SRS.