Prospectively Observed Histopathologic Predictors of Progression after Stereotactic Radiosurgery for Recurrent Atypical Meningioma

Abstract

<h3>Purpose/Objective(s)</h3> Atypical meningiomas (AM) have high rates of progression and recurrence after initial treatment. Optimal management of recurrent AM remains an unresolved issue. In turn, we sought to correlate histopathologic findings of AM at initial resection with survival outcomes after stereotactic radiosurgery (SRS) for treatment of recurrent disease. <h3>Materials/Methods</h3> Prospectively enrolled radiation-naïve patients who were treated with SRS for recurrent AM between 2014 and 2020 were retrospectively reviewed in our institutional review board (IRB) approved database. Kaplan-Meier analysis with log rank testing was used to compare local control and survival in patients with varying histopathological features and Cox regression was used to examine possible prognostic factors for progression after SRS. <h3>Results</h3> Two hundred and seventy-seven patients with meningioma were treated with SRS from 2014 to 2020. Of these, 49 were identified who underwent resection for an atypical meningioma at our institution and then received salvage SRS for first recurrence. Forty-five (92%) patients received salvage radiation after recurrence following a subtotal resection (STR) and four patients (8%) received salvage radiation for recurrent disease after an initial gross total resection (GTR). Patients receiving salvage SRS underwent treatment for recurrent disease at a mean time of 23 months after surgery. Tumor size was not associated with progression after SRS treatment. On univariable analysis, presence of necrosis, presence of brain invasion, and presence of bone invasion predicted for progression. At 2 years, patients treated with SRS had a local control rate of 93%. In the subset of patients found to have necrosis, bone invasion, or brain invasion on surgical pathology, local control at 2 years was 81%. <h3>Conclusion</h3> Histopathologic variables can predict for treatment outcomes of recurrent atypical meningioma treated with radiotherapy and should be considered when deciding on an individual patient's treatment plan in the setting of recurrence. Brain and bone invasion as well as presence of necrosis predict for decreased local control after SRS. Future investigation is warranted to optimize outcomes in this group.