Radiotherapy for meningiomas

Abstract

Meningiomas are the most common primary central nervous system neoplasm. Despite promising recent progress in elucidating the genomic landscape and underlying biology of these histologically, molecularly, and clinically diverse tumors, the mainstays of meningioma treatment remain maximal safe resection and radiation therapy. The aim of this review of meningioma radiotherapy is to provide a concise summary of the history, current evidence, and future for application of radiotherapy in meningioma treatment.

Keywords: Anaplastic; Atypical; DOTATATE; Meningioma; Molecular; Radiation; Radiotherapy.

Fig. 1

Evolution of meningioma radiotherapy. A–B Figures reproduced from Friedman et al. 1977 [5]. A shows an early example of meningioma radiotherapy. Shown is a 2D film described as a verification “post film” showing a cylindrical irradiated volume targeting a large posterior fossa meningioma, treated sometime before 1963. This volume received a maximum dose of 8000 rad (80 Gy) in 42 days with 2MV photons, a significantly higher dose than reported by most investigators, past or present. This patient was reportedly alive and well 4 years post-radiation. B shows a diagram from the same historical publication showing a mock-up of a 2D technique using tangential fields with physical wedges for treatment of a parasagittal meningioma. C–D shows an axial post-contrast T1 MRI and IMRT plan delivering 59.4 Gy in 33 fractions, respectively, for a large 4.8 cm left frontoparietal meningioma. Gross total resection was achieved, and pathology revealed 5 mitoses per 10hpf, foci of necrosis, hypercellularity and small cell change. No brain invasion was identified, and Ki67 labeling index was 5%. Immunohistochemistry staining showed retained H3K27me and BAP1. An institutional targeted DNA sequencing panel revealed monosomy 22q and a pathogenic NF2 mutation, along with loss of 1p, 10p and 14q, consistent with high molecular risk. In D), the red line denotes the 59.4 Gy prescription isodose, and blue denotes the 50% isodose line. The target included a customized anisotropic margin of at-risk dura of up to 15 mm, and no explicit clinical target volume expansion into brain, given the absence of brain invasion. E–F shows an axial post-contrast T1 MRI of an imaging defined, presumed benign meningioma abutting the brainstem, which was treated with 54 Gy in 30 fractions (red isodose line). Treatment was well tolerated. G–H shows coronal post-contrast T1 MRI and IMRT plan delivering 59.4 Gy in 33 fractions, respectively, for a large, heterogenous and multilobulated meningioma of the posterior falx, which underwent a gross-total resection. Pathology revealed 11 mitoses per 10 high powered fields, elevated Ki67 labeling index of 7%, foci of necrosis, small cell change, consistent with WHO grade 2. Immunohistochemistry showed weak progesterone receptor staining in ~ 25% of cells and retained H3K27me3. An institutional targeted DNA sequencing panel showed no pathogenic SSVs, but chromosomes 22q (NF2), 1p, and 19q were lost, consistent with high molecular risk. The target included a customized anisotropic margin of up to 15 mm of at-risk falx and dura, including the sagittal dural sinus abutted by tumor. Treatment was well tolerated, and the patient remains disease free 1.5 years post-therapy