title: Malignant progression of benign brain tumors after gamma knife radiosurgery: is it really caused by irradiation?
abstract: Malignant transformation of benign neoplasm after radiosurgery is usually diagnosed based on the initial presence of benign tumor, its exposure to ionizing radiation, elapsed time from radiation exposure to malignant progression, and different histological characteristics or growth rate of the regrowing tumor comparing with those originally treated. Three presented cases fulfilled these diagnostic criteria; however, it seems that progression of the tumors (schwannoma, meningioma, chordoma) resulted from the natural course of the disease, rather than represented side effects of gamma knife radiosurgery. Evaluation of the proliferative potential of the benign neoplasm before radiosurgical treatment either directly, if tumor sampling is available, or indirectly, by calculation of the tumor growth rate and/or analysis of the data of the metabolic imaging (PET, MRS) is important for identification of "aggressive" subtypes, precise prediction of prognosis, and confirmation of the radiation-induced malignant transformation in cases of tumor regrowth.
authors.affiliation: Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. okubo@nij.twmu.ac.jp
authors.forename: O
authors.initials: O
authors.lastname: Kubo
authors.forename: M
authors.initials: M
authors.lastname: Chernov
authors.forename: M
authors.initials: M
authors.lastname: Izawa
authors.forename: M
authors.initials: M
authors.lastname: Hayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Muragaki
authors.forename: T
authors.initials: T
authors.lastname: Maruyama
authors.forename: T
authors.initials: T
authors.lastname: Hori
authors.forename: K
authors.initials: K
authors.lastname: Takakura
mesh_terms: D000328:Adult; D001927:Brain Diseases / Q000601:surgery; D001932:Brain Neoplasms / Q000473:pathology / Q000601:surgery*; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects*; D002817:Chordoma / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology / Q000601:surgery*; D008579:Meningioma / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000503:physiopathology*; D009442:Neurilemmoma / Q000473:pathology / Q000601:surgery*; D011379:Prognosis; D016634:Radiosurgery / Q000009:adverse effects*