Treatment of Radiation-Induced Meningiomas With Non-Invasive Stereotactic Radiosurgery

Abstract

Radiation-Induced Meningiomas (RIMs) are one of the most common secondary malignancies from prior brain irradiation and are known to be recurrent. While Gamma Knife (GK) radiosurgery is routinely employed for the treatment of sporadic meningiomas, data on its use for RIMs are limited. Here, we assessed whether the use of GK radiosurgery for RIMs can achieve > 80% local control at 1 year.We retrospectively reviewed our institution's GK database from 08/31/99 - 10/08/20. Meningiomas were considered radiation-induced if they met Cahan's criteria: (1) occurred after brain radiation for a previous neoplasm, (2) were within the previous radiation field, and (3) had a distinct histology or radiographic appearance from previously treated neoplasm. Patients with a genetic predisposition for tumor formation were excluded. Endpoints included overall survival (OS), progression free survival (PFS), local failure (within 2cm of GK field), and distant failure. Toxicity was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0.A total of 29 patients with 86 RIM lesions were identified from 1999 to 2020 and followed for a median of 59 months. Of these patients, 20 had WHO grade I (n = 4) or presumed grade I (n = 20) RIMs and 5 had WHO grade II RIMs. The median latency time from previous brain irradiation to initial SRS was 26 years. The median dose prescribed to the 50% isodose line was 14 Gy (range 12-20 Gy) with a median lesion volume of 2 cm3. The actuarial 5-yr OS and 5-yr PFS were 95% and 70%, respectively. Patients who were treated for recurrent RIMs after previous surgery had a significantly lower 5-yr OS (88% vs 100%; log-rank, P < 0.0046) and 5-yr PFS (39% vs 81%; log-rank, P < 0.005) than patients who were treated in the upfront setting. On a per-lesion basis, local control at 1-, 3-, and 5-yrs was 82%, 76%, 74%, respectively. Presumed or WHO grade I RIMs had a significantly greater 5-yr local control than WHO grade II RIMs (100% vs 56%, log-rank, P < 0.001). The rate of distant failure at 1-, 3-, and 5-yrs was 3.5%, 18%, and 32%, respectively. At time of progression, 5 patients had distant failures, while 3 patients had local and distant failures. Failures were salvaged through additional GK (n = 8), surgery (n = 2), or chemotherapy (n = 1). The crude incidence of grade 1-3 toxicity from GK was 10% (n = 3). No grade 4 or 5 adverse events were recorded. Only 1 patient developed grade 3 toxicity (cranial nerve neuropathy), which resolved with steroids.This is the largest series of RIM lesions treated with GK radiosurgery. RIMs are associated with a high OS and GK radiosurgery provides satisfactory PFS and local control. Recurrent and WHO grade II lesions are associated with lower PFS and local control after radiosurgery than upfront and WHO grade I lesions. The majority of failures after GK are distant. Treatment using GK radiosurgery has minimal morbidity. It should be considered for patients or tumors that are not candidates for surgical resection.N.Razavian: None. C.A.Helis: None. A.Laxton: None. S.B. Tatter: None. J.Bourland: None. R.T. Mott: None. G.J. Lesser: None. R.Strowd: None. M.D. Chan: None. C.K. Cramer: None.