Investigation into the Effect of Immunosuppression on Clinical Outcomes after Stereotactic Radiosurgery for Treatment of Vestibular Schwannoma

Objective: Stereotactic radiosurgery (SRS) is an established treatment for small- to medium-sized vestibular schwannomas (VS). While the mechanism by which SRS arrests tumor growth is thought to be multi-pronged, part of the treatment effect may be mediated by SRS-induced tumoral inflammation, followed by an anti-tumoral immune response. There is a paucity of data on whether pre-existing immunosuppression can alter the efficacy of SRS when used to treat VS.

Methods: We retrospectively reviewed the clinical and radiographic records of patients with a treatment-naïve, non-neurofibromatosis type II-associated VS undergoing SRS from 2005 to 2015. Patients receiving immunosuppressive medications at the time of SRS were identified, and demographic and tumor characteristics were noted, as were pre- and post-SRS audiogram results. The primary outcome of interest was treatment failure, which was defined as continued growth on serial imaging following SRS and/or the need for salvage therapy. A secondary outcome of interest was retention of class A hearing (≥70% word recognition) during follow-up. Comparative statistics between immunosuppressed and non-immunosuppressed patients were performed, and variables associated with treatment failure and retention of class A hearing were identified using a Cox proportional hazards model.

Results: There were 303 patients with VS who were treated with SRS during the study period. The mean age of the cohort was 61.2 years (standard deviation [SD]: 11.6), and a slight majority of patients were female (n = 153, 50.5%). There were 11 patients (3.6%) receiving immunosuppressive medications at the time of SRS. The mean treated tumor volume was 1.619 cm³, with mean marginal and maximum doses of 12.7 and 25.3 Gy, respectively. Sustained growth on serial imaging after SRS was seen in 37 cases (12.2%), with 26 patients (8.6%) undergoing some form of salvage therapy. The incidence of sustained growth (n = 2/11, 18.2%) or need for salvage therapy (n = 1/11, 9.1%) among immunosuppressed patients was not significantly different than that among non-immunosuppressed patients (p > 0.05), and immunosuppression was not associated with the need for salvage therapy in a Cox proportional hazards model (RR: 0.95, 95% CI: 0.13–7.03; p = 0.96). There were 138 patients with ≥70% word recognition on audiologic testing prior to SRS who underwent follow-up audiograms after SRS. The percentages of immunosuppressed and non-immunosuppressed patients who retained class A hearing during follow-up were 45.0% (n = 59/131) and 71.4% (n = 5/7; p = 0.17). Immunosuppression was not associated with retention or loss of class A hearing on a Cox proportional hazards model (RR: 0.38, 95% CI: 0.09–1.53; p = 0.17).

Conclusion: Our results do not suggest an effect of immunosuppressed status on the efficacy of SRS for the treatment of VS, though our sample size was too small to draw any definitive conclusions. Additional investigation on this subject is warranted.

Publikationsverlauf

Artikel online veröffentlicht:
15. Februar 2022