Hypofractionated irradiation for intracranial meningiomas

Hypofractionated irradiation of meningiomas is a relevant fractionation regimen that occupies an intermediate position between radiosurgery and standard fractionation. This study analyzed the experience with this regimen in the Radiotherapy Department of the Burdenko National Medical Research Center of Neurosurgery to evaluate the method's efficacy and safety. A retrospective analysis included patients who underwent radiation therapy between 2017 and 2020. The study included 73 patients. The median age was 56, and the male-to-female ratio was 1:5. Nine patients were diagnosed with schwannomatosis (neurofibromatosis type 2), and 12 had multiple meningiomas. A total of 94 meningiomas were treated with hypofractionation in regimens of 3 and 5 fractions. Twenty eight tumors (29.8%) were previously verified as WHO grade 1 (25) and grade 2 (3). The median target volume was 5.6 cm³ (range 0.2 to 28.9 cm³). Data for analysis were available for 60 patients with 80 tumors, which did not differ significantly in baseline characteristics from the entire group. The local 3-year and 5-year control rate for meningiomas was 95%. Local control did not differ between sporadic tumors and those associated with schwannomatosis and multiple meningiomas. Tumor control was not influenced by volume, number of fractions, dose, treatment platform, histological verification status, or tumor location (skull base vs. convexity). Radiation reactions within 12 months after treatment were detected in 5 tumors (6.3%). The presence of pre-existing peritumoral edema significantly increased the risk of radiation reactions to 60%. A reduction in meningioma size was observed in 61.3% of cases. The median tumor volume reduction was 37% (range 8-84%). This study identified 2 cases (2.5%) of radiation-induced pathomorphosis in the form of appearance and prolonged existence/progression of cysts, which is generally an uncharacteristic clinical course for meningiomas. Thus, hypofractionation is an effective and sufficiently safe method of radiation therapy for meningiomas, enabling the more frequent use of shortened radiation treatment courses instead of prolonged standard fractionation regimens. Given the rare recurrence of meningiomas and the low complication rate, larger and longer-term studies are needed to clarify all factors influencing the outcomes of radiation therapy.