Surgeon-Planned Subtotal Resection of Vestibular Schwannoma Diverges from the Optimal Radiosurgical Target Defined by Adaptive Hybrid Surgery Software

Background Preferred operative management of vestibular schwannoma (VS) has shifted in the past decade from the more aggressive goal of gross total resection (GTR) to a multimodal approach of planned subtotal resection (STR) with adjuvant radiosurgery.

Objective To compare optimal radiosurgical target volumes defined by a manual method (surgeon) to those determined by operative planning software (Adaptive Hybrid Surgery software) in seven VS cases.

Methods First, planned residual tumor volumes were manually contoured by four attending surgeons. Second, optimal radiosurgical target volumes were determined using AHS software. Our primary measure of interest was the difference between average surgeon-planned residual tumor volumes and optimal radiosurgical target volumes defined by AHS (dRVAHS-planned).

Results Seven consecutive VS patients were included in this study. Surgeon-planned residual tumor volumes were smaller than optimal radiosurgical targets defined by AHS (1.6 vs. 4.5 cm³, p = 0.004). Actual postoperative residual volumes were also smaller than optimal radiosurgical target volumes defined by AHS (4.5 vs. 2.2 cm³, p = 0.02), and did not differ from the average surgeon-planned residual volumes (p = 0.35). Average dRVAHS-planned was 2.9 ± 1.7 cm³ and we observed a trend toward larger dRVAHS-planned in patients who lost serviceable facial nerve function compared with patients who maintained serviceable facial nerve function at last clinical follow-up (4.7 vs. 1.9 cm³, p = 0.06).

Conclusion Surgeon-planned STR of VS diverges from the optimal radiosurgical target defined by AHS software. However, it is unclear whether this impacts clinical outcomes or adjuvant therapy. There is a need for continuing education on radiosurgery principles for neurosurgeons considering the use of AHS software.