Clinical Outcomes of Recurrent Intracranial Meningiomas Treated with Proton Beam Reirradiation.

Brandon S. Imber, Brian Neal, Dana L. Casey, Heba Darwish, Andrew L. Lin, Oren Cahlon, Brian Chon, Henry Tsai, Eugen Hug, Yoshiya Yamada, and T. Jonathan Yang (2019) International Journal of Particle Therapy: Spring 2019, Vol. 5, No. 4, pp. 11-22.

Proton beam radiation therapy (PBRT) offers a dosimetric advantage for reRT, especially for patients with multiple prior courses of RT, owing to improved ability to spare toxicity to nearby normal structures.

PBRT reRT may be a relatively efficacious strategy for recurrent meningiomas, a patient population lacking durable therapeutic options. Even with significant prior radiation exposure, radionecrosis rates appear low. We feel that prospective investigation of the modality is warranted to validate incremental improvement over traditional photon RT.

Proton and photon comparative dosimetry for a 72-year-old man with an anaplastic meningioma of the right cavernous sinus. (A) Original photon IMRT plan, which delivered 59.4 Gy in conventional fractionation. (B) Nodular area of T1 post contrast enhancement posterior to the right carotid artery suggestive of in-field recurrence (yellow arrow). (C) Proton reirradiation plan delivered to 60 Gy(RBE) in 2 Gy(RBE) fractions with 2 beams and uniform scanning. (D) Hypothetical comparison reirradiation plan using photon VMAT (not delivered). (E) Cumulative dose delivered by using proton beam radiation therapy. (F) Hypothetical cumulative dose delivered had photon VMAT plan been delivered. (G) Isodose lines in Gy for plans in (A), (C), and (D). (H) Cumulative isodose lines in Gy(RBE) for plans in (E) and (F). Abbreviations: IMRT, intensity-modulated radiation therapy; VMAT, Volumetric Modulated Arc Therapy.