Prediction of treatment failure and early identification of tumor progression after Gamma-Knife radiosurgery in vestibular schwannoma: A retrospective cohort study.

BACKGROUND

Microsurgical resection after failed radiosurgery (SRS) in vestibular schwannoma (VS) patients is associated with higher morbidity. Identifying factors that predict treatment failure (TF) is crucial. Additionally, distinguishing between pseudoprogression (PP) and true tumor progression (TP) can be challenging. This study aims to identify predictive factors for TF and investigate early features that differentiate PP from TP.

METHODS

A retrospective analysis was performed on 705 patients with unilateral sporadic VS who underwent SRS between 1998 and 2020. Clinical data, including patient characteristics, symptoms, tumor volume (TV), and onset of new symptoms after SRS, were recorded. The average follow-up was 4 years for the TP group ( = 107) and 7 years 10 months for the remission group ( = 598).

RESULTS

TF was more common in women ( = .04) and linked to lower OHATA class ( = .03). Age, clinical symptoms, TV, and configuration (cystic vs solid) were not predictive of TF. TP-patients experienced significantly more new neurological symptoms (20.6% vs 8.4%,  < .001), especially hemifacial spasm ( < .001), which was associated with OHATA class (A > B > C > D > E,  = .001). Relative TVs (RTV) differed significantly between TP and tumor control (TC) groups, with the TP group showing higher RTV at both 12 months (TC = 1.0 ± 0.6, TP = 1.4 ± 1,  = .002) and even more at 24 months (TC = 0.71 ± 0.5, TP = 1.5 ± 0.7,  < .001) after SRS.

CONCLUSIONS

Female sex and lower OHATA class were identified as independent predictors of TF. Hemifacial spasm occurrence after SRS was linked to TP. Failure of reduction of initial TV (RTV > 1) after 24 months was associated with TP with a high sensitivity and specificity, making PP unlikely.