Repeat Radiosurgery for Sporadic Vestibular Schwannoma After Primary Radiosurgical Failure: An International Multi-institutional Investigation.

[OBJECTIVE] To describe outcomes of patients with sporadic vestibular schwannoma (VS) who underwent repeat stereotactic radiosurgery (SRS) after primary SRS failure.

[STUDY DESIGN] Multi-institutional historical cohort study.

[SETTING] Five tertiary care referral centers.

[PATIENTS] Adults ≥18 years old with sporadic VS.

[INTERVENTION] Primary and repeat treatment with SRS.

[MAIN OUTCOME MEASURE] Microsurgery-free survival after repeat SRS.

[RESULTS] Across institutions, 32 patients underwent repeat SRS after primary SRS. Most patients (74%) had tumors with cerebellopontine angle extension at primary SRS (median size, 13.5 mm [interquartile range, 7.5-18.8] mm). After primary SRS, patients underwent repeat SRS at a median of 4.8 years (interquartile range, 3.2-5.7 yr). For treatment modality, 30 (94%) patients received gamma knife for primary treatment and 31 (97%) patients received gamma knife as their repeat treatment. Median tumor volume increased from 0.970 cm3 at primary SRS to 2.200 cm3 at repeat SRS. Facial nerve function worsened in two patients after primary SRS and in two patients after repeat SRS. There were no instances of intracranial complications after repeat SRS. Microsurgery-free survival rates (95% confidence interval; number still at risk) at 1, 3, and 5 years after repeat SRS were 97% (90-100%, 24), 84% (71-100%, 13), and 68% (48-96%, 6), respectively. There was one occurrence of malignancy diagnosed after repeat radiosurgery.

[CONCLUSION] Overall, repeat SRS for sporadic VS has comparable risk profile, but lower rates of tumor control, compared with primary SRS.