Abstract
Recurrent meningiomas remain therapeutically challenging, often progressive despite multimodality salvage. There are limited data guiding reirradiation (reRT), and proton beam radiation therapy (PBRT) offers a potential advantage owing to lower integral brain dose. We retrospectively conducted a review of 16 patients who received PBRT reRT for recurrent meningiomas. Kaplan-Meier and proportional hazards were used to determine post-PBRT progression-free survival (PFS) and overall survival (OS) and to evaluate clinical predictors. At diagnosis, 7 (44%), 8 (50%), and 1 (6%) patient had World Health Organization (WHO) grade I, II and III tumors, respectively. All received prior radiation therapy (RT) to a median of 54 Gy (range 13-65.5). Median time to PBRT reRT after prior RT was 5.8 years (range 0.7-18.7). Median PBRT dose was 60 Gy(RBE) (range 30-66.6), and median planning tumor volume (PTV) was 76 cm3 (range 8-249). Median follow-up was 18.8 months. At last follow-up, 7 intracranial recurrences (44%) and 3 disease-related deaths (19%) were found. Median cohort PFS was 22.6 months, with 1- and 2-year PFS of 80% and 43%, respectively. Median OS was not achieved, with 1- and 2-year OS of 94% and 73%; all deaths were felt to be related to meningioma. Patients with initially grade I tumors had improved PFS versus higher grade (Hazard Ratio, HR = 0.23, P = .03) with 1- and 2-year PFS estimates of 100% versus 71% and 75% versus 29%, respectively. Longer interval between prior RT and PBRT also predicted improved PFS (P = .03) and OS (P = .049). Overall late grade 3+ toxicity rate was 31%. Two patients (13%) developed radionecrosis at 6 and 16 months after PBRT; only 1 was symptomatic. This is the first series specifically analyzing PBRT alone as a reRT strategy for recurrent meningioma. We report fair intracranial control with low rates of radionecrosis at 1 year after reRT. However, strategies to achieve durable outcomes are needed, particularly for high-grade tumors.
Highlights
Meningiomas are the most common primary central nervous system tumor [1]
We found that histologic grade is a significant predictor of local failure (Hazard Ratio, hazard ratio (HR) 4.4, 95% CI 1.07-18.0, P 1⁄4 .03) with higher-grade tumors at greater risk for progression after proton beam radiation therapy (PBRT) reRT
We present a contemporary series of patients who underwent reRT using proton beam radiation for recurrent intracranial meningioma and report fair local control and overall survival (OS) with acceptable toxicity
Summary
Meningiomas are the most common primary central nervous system tumor [1]. Active surveillance is generally accepted for small, incidentally discovered or asymptomatic lesions and maximal safe surgical resection remains the mainstay of treatment for large or symptomatic tumors. Multiple studies have retrospectively investigated recurrence risks after RT and reported rates of 0% to 23% (typically ,10% for modern series) for World Health Organization (WHO) grade I lesions, using either EBRT or SRS [8]. A large retrospective series from Korea reported a 7.3% total recurrence rate for patients with a single meningioma who underwent Gamma Knife radiosurgery [9]. Rates of failure for higher-grade lesions are significantly increased, though immediate adjuvant RT, to higher doses, does appear to improve outcomes [10]. This was confirmed by the recently reported prospective RTOG 0539 trial, which reported a benefit for adjuvant RT for intermediate-risk meningiomas [11]
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