Salvage Microsurgery Following Failed Primary Radiosurgery in Sporadic Vestibular Schwannoma

Abstract

Importance: Management of sporadic vestibular schwannoma with radiosurgery is becoming increasingly common globally; however, limited data currently characterize patient outcomes in the setting of microsurgical salvage for radiosurgical failure.

Objective: To describe the clinical outcomes of salvage microsurgery following failed primary stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) among patients with sporadic vestibular schwannoma.

Design, setting, and participants: This was a cohort study of adults (≥18 years old) with sporadic vestibular schwannoma who underwent salvage microsurgery following failed primary SRS/FSRT in 7 vestibular schwannoma treatment centers across the US and Norway. Data collection was performed between July 2022 and January 2023, with data analysis performed between January and July 2023.

Exposure: Salvage microsurgical tumor resection.

Main outcomes and measures: Composite outcome of undergoing less than gross total resection (GTR) or experiencing long-term facial paresis.

Results: Among 126 patients, the median (IQR) age at time of salvage microsurgery was 62 (53-70) years, 69 (55%) were female, and 113 of 117 (97%) had tumors that extended into the cerebellopontine angle at time of salvage. Of 125 patients, 96 (76%) underwent primary gamma knife SRS, while 24 (19%) underwent linear accelerator-based SRS; the remaining patients underwent FSRT using other modalities. Postoperative cerebrospinal fluid leak was seen in 15 of 126 patients (12%), hydrocephalus in 8 (6%), symptomatic stroke in 7 (6%), and meningitis in 2 (2%). Each 1-mm increase in cerebellopontine angle tumor size was associated with a 13% increased likelihood of foregoing GTR (64 of 102 patients [63%]) or long-term postoperative House-Brackmann grade higher than I (48 of 102 patients [47%]) (odds ratio, 1.13; 95% CI, 1.04-1.23). Following salvage microsurgery, tumor growth-free survival rates at 1, 3, and 5 years were 97% (95% CI, 94%-100%), 93% (95% CI, 87%-99%), and 91% (95% CI, 84%-98%), respectively.

Conclusions: In this cohort study, more than half of patients who received salvage microsurgery following primary SRS/FSRT underwent less than GTR or experienced some degree of facial paresis long term. These data suggest that the cumulative risk of developing facial paresis following primary SRS/FSRT by the end of the patient's journey with treatment approximates 2.5% to 7.5% when using published primary SRS/FSRT long-term tumor control rates.

Figure.. Comparison of Tumor Size Among Patients at Time of Salvage

Box plot comparing tumor size within the cerebellopontine angle (CPA) for patients who underwent gross total resection (GTR) and achieved most recent postoperative House-Brackmann (HB) grade I facial function compared with those who underwent near-total resection (NTR) or subtotal resection (STR) or experienced long-term HB grade higher than I facial function. The 25th and 75th percentiles of tumor size are depicted as the borders of the box surrounding the solid black line indicating the median tumor size, with the whiskers on either end of the box demarcating the range observed. Each dot represents tumor size for an individual patient.