Proton Therapy for Intracranial Meningioma for the Treatment of Primary/Recurrent Disease Including Re-Irradiation

Abstract

Meningeal tumors represent approximately 10–25% of primary brain tumors and occur usually in elderly female patients. Most meningiomas are benign (80–85%) and for symptomatic and/or large tumors, surgery, with or without radiation therapy (RT), has been long established as an effective means of local tumor control. RT can be delivered to inoperable lesions or to those with non-benign histology and for Simpson I–III and IV–V resection. RT can be delivered with photons or particles (protons or carbon ions) in stereotactic or non-stereotactic conditions. Particle therapy delivered for these tumors uses the physical properties of charged carbon ions or protons to spare normal brain tissue (i.e. Bragg peak), with or without or a dose-escalation paradigm for non-benign lesions. PT can substantially decrease the dose delivered to the non-target brain tissues, including but not limited to the hippocampi, optic apparatus or cochlea. Only a limited number of meningioma patients have been treated with PT in the adjuvant or recurrent setting, as well as for inoperable lesions with pencil beam scanning and with protons only. Approximately 500 patients with image-defined or WHO grade I meningioma have been treated with protons. The reported outcome, usually 5-year local tumor control, ranges from 85 to 99% (median, 96%). For WHO grade II or III patients, the outcome of only 97 patients has been published, reporting a median tumor local control rate of 52% (range, 38–71.1). Only 24 recurring patients treated previously with photon radiotherapy and re-treated with PT were reported. The clinical outcome of these challenging patients seems interesting, provided that they presented initially with benign tumors, are not in the elderly category and have been treated previously with conventional radiation dose of photons. Overall, the number of meningioma patients treated or-re-irradiated with this treatment modality is small and the clinical evidence level is somewhat low (i.e. 3b–5). In this review, we detail the results of upfront PT delivered to patients with meningioma in the adjuvant setting and for inoperable tumors. The outcome of meningioma patients treated with this radiation modality for recurrent tumors, with or without previous RT, will also be reviewed.

Quality of Life, Clinical, and Patient-Reported Outcomes after Pencil Beam Scanning Proton Therapy Delivered for Intracranial Grade WHO 1–2 Meningioma in Children and Adolescents

“…The favorable local control rates of PT in the adult population have been described in a recent review [ 55 ], and this technique is included in the most recent National Comprehensive Cancer Network guidelines for meningioma [ 56 ]. In those situations where the characteristics of the target volume do not allow stereotactic treatment, protons would offer a potential benefit compared to photon treatment in the pediatric and adolescent population due to the reduction in the integral dose to the surrounding tissues, which may associate a reduction in long-term side effects such as neurocognitive detriment and secondary tumors [ 28 , 57 , 58 ].…”

Long Term Outcome and Quality of Life of Intracranial Meningioma Patients Treated with Pencil Beam Scanning Proton Therapy

“…20% of all meningioma patients treated with this radiation modality whose outcomes have been reported in the recent literature. The standard of care for meningiomas treated with radical, salvage, or adjuvant radiotherapy is the use of highly conformal photon radiotherapy techniques, such as intensitymodulated radiotherapy, fractioned radiotherapy, or radiosurgery [26]. As meningiomas are frequently in a close relationship with important OARs such as the optic apparatus or brainstem [27], a highly conformal radiotherapy such as stereotactic photon RT or PBS PT is preferred.…”

Spinal Meningiomas: A Comprehensive Review and Update on Advancements in Molecular Characterization, Diagnostics, Surgical Approach and Technology, and Alternative Therapies

“…Although radiotherapy, including both fractionated external-beam radiation and SRS, can be used as a primary treatment with some benefit, its utility remains most efficacious as an adjuvant therapy following surgical resection. Finally, proton therapy has gained traction in its use to treat intracranial meningiomas due to a proton's ability to achieve an improved dose conformation compared to photons, ultimately sparing healthy tissue [145]. However, there are currently no studies to date which have investigated its efficacy in spinal meningiomas.…”