Patterns Of Failure After Adjuvant Radiation For Meningioma, Radiologic Assessment To Inform Target Delineation And Treatment Planning

Abstract

Adjuvant radiotherapy is increasingly used for intermediate and high-risk meningioma, and although short-term results from prospective trials demonstrate good rates of local control, long-term failures remain common. Moreover, the optimal expansions for postoperative radiotherapy target delineation for meningioma are unknown. We sought to elucidate the patterns of failure after adjuvant radiotherapy for meningioma to inform target delineation and treatment planning. Patients undergoing surgical resection for meningioma at a single institution were retrospectively reviewed for treatment with adjuvant radiation therapy, including external beam radiation therapy (EBRT), stereotactic radiosurgery (SRS), or brachytherapy. Patients treated with EBRT were evaluated for patterns of failure based on MRI review, and were classified as resection cavity, dural margin, osseous craniotomy tract, and intraparenchymal brain. Analysis was performed to evaluate factors associated with each failure type, and to identify the radiologic distance from the resection cavity margin to the furthest margin of each site of recurrent disease. From 1991 to 2015, 71 patients with 86 lesions were treated with adjuvant radiation therapy after resection of meningioma. The median follow-up was 4.2 years (IQR: 1.5-8.4 years). There were 14 (16%) grade 1, 49 (57%) grade II, and 23 (27%) grade III meningiomas, and gross total resection was achieved in 53 (61.6%) of cases. There were 22 local failures after EBRT, 16 (72.7%) were in-field, 11 (50%) were at the dural margin, 2 (9.1%) were along a craniotomy track, and 2 (9.1%) were intraparenchymal. In patients with dural marginal failure, the median distance from the edge of the resection cavity to the distal extent of the recurrence was 15 mm (IQR: 13-24 mm). Of the resection cavity recurrences, 5 (31.2%) occurred within 10 mm of the apex of the orbit or the cavernous sinus. The median MIB1 labeling index in meningioma with either intraparenchymal or craniotomy tract failure was 31.0%, compared to 11.3% (p = 0.018) in patients with infield or dural margin failure. Local failure along the dural margin after adjuvant radiation therapy for meningiomas occurred a median of 15 mm from the resection cavity. Failure along the craniotomy tract or parenchymal brain was uncommon, and was associated with a significantly higher MIB1, likely reflecting more aggressive tumor biology. These data may help to inform target delineation and margin expansion for patients receiving adjuvant radiotherapy for meningioma.