Meningiomas are the second most common primary tumor of the brain. Surgical resection is the preferred treatment for easily accessible tumors that can be safely removed. However, many tumors arise deep within the skull base making complete surgical resection difficult or impossible. Stereotactic radiosurgery is a highly effective alternative to surgical resection that has been used as a primary therapy for benign meningiomas as well as an adjuvant treatment for residual or recurrent tumors. The 5-year tumor control rates for stereotactic radiosurgery are equivalent to gross-total resection with lower morbidity than surgery, especially for skull base lesions. Additionally, adjuvant treatment of subtotally resected tumors results in tumor control rates equivalent to gross-total resection. Stereotactic radiosurgery has been used extensively for the treatment of small and medium sized skull base meningiomas. This technique has also been applied to large meningiomas and superficial tumors such as convexity and parasagittal meningiomas. However, multiple studies demonstrate that tumor control is decreased for superficial lesions and with increasing tumor size. In addition, radiation toxicity increases with increasing tumor size and superficial location. Based on a thorough review of the literature, stereotactic radiosurgery should be considered the primary treatment for skull base meningiomas with high surgical risk and in cases of superficial meningiomas where surgery is contraindicated.
"This safety is derived from delivering highly precise radiation using a stereotactic frame with judicious dose selection and image guidance systems   . Large data sets have been generated demonstrating the feasibility, safety, and efficacy of stereotactic radiosurgery and fractionated stereotactic radiotherapy for meningioma       . These data sets include the use of different machines, typically Gamma Knife or linear accelerators, and different techniques and anatomic locations. "
[Show abstract][Hide abstract] ABSTRACT: Objectif de l’étude
L’objectif de l’étude était d’analyser la faisabilité, l’innocuité et l’efficacité à long terme de la radiothérapie stéréotaxique fractionnée de méningiomes de la base du crâne. Nous avons évalué les résultats à long terme et identifié les facteurs pronostiques.
Patients et méthodes
Entre octobre 1995 et mars 2009, 136 patients d’âge médian 57 ans ont été traités par irradiation stéréotaxique fractionnée pour un méningiome de la base du crâne. Trente-quatre patients étaient atteints d’un méningiome de grade I, tandis que pour les 102 autres patients l’histologie n’était pas disponible (grade 0). Sur ces 136 patients, l’irradiation était de première intention pour 57 et elle était postopératoire pour 79. Les patients ont reçu une dose totale moyenne de 56,95 Gy (32,4 Gy–63 Gy).
Le suivi médian était de 44,9 mois. La probabilité de survie sans progression était de 96,9 % à 3 ans, 93,8 % à 5 ans et 91,5 % à 10 ans. Elle était en cas d’histologie indisponible, respectivement de 100 %, 98,7 %, et 93,5 % et en cas de méningiome de grade I, prouvé par biopsie, de 100 %, 91,7 % et 85,9 %. Si la radiothérapie était adjuvante, elle était significativement inférieure (p = 0,043), et elle était indépendante de la taille de la tumeur. Les symptômes aigus de grade I les plus courants étaient des céphalées, la fatigue, et l’alopécie locale, les symptômes chroniques de grade I les plus courants la fatigue et des céphalées.
Cette grande étude montre que la radiothérapie stéréotaxique fractionnée est un traitement efficace et sans danger pour les méningiomes de la base du crâne, avec des probabilités élevées de survie sans progression. De plus, nous avons mis en évidence que la chirurgie associée à la radiothérapie représente un facteur pronostique défavorable.
[Show abstract][Hide abstract] ABSTRACT: While most meningiomas are benign, aggressive meningiomas are associated with high levels of recurrence and mortality. A single institution's Gamma Knife radiosurgical experience with atypical and malignant meningiomas is presented, stratified by the most recent WHO classification.
Thirty-one patients with atypical and 4 patients with malignant meningiomas treated with Gamma Knife radiosurgery between July 2000 and July 2011 were retrospectively reviewed. All patients underwent prior surgical resection. Overall survival was the primary endpoint and rate of disease recurrence in the brain was a secondary endpoint. Patients who had previous radiotherapy or prior surgical resection were included. Kaplan-Meier and Cox proportional hazards models were used to estimate survival and identify factors predictive of recurrence and survival.
Post-Gamma Knife recurrence was identified in 11 patients (31.4%) with a median overall survival of 36 months and progression-free survival of 25.8 months. Nine patients (25.7%) had died. Three-year overall survival (OS) and progression-free survival (PFS) rates were 78.0% and 65.0%, respectively. WHO grade II 3-year OS and PFS were 83.4% and 70.1%, while WHO grade III 3-year OS and PFS were 33.3% and 0%. Recurrence rate was significantly higher in patients with a prior history of benign meningioma, nuclear atypia, high mitotic rate, spontaneous necrosis, and WHO grade III diagnosis on univariate analysis; only WHO grade III diagnosis was significant on multivariate analysis. Overall survival was adversely affected in patients with WHO grade III diagnosis, prior history of benign meningioma, prior fractionated radiotherapy, larger tumor volume, and higher isocenter number on univariate analysis; WHO grade III diagnosis and larger treated tumor volume were significant on multivariate analysis.
Atypical and anaplastic meningiomas remain difficult tumors to treat. WHO grade III diagnosis and treated tumor volume were significantly predictive of recurrence and survival on multivariate analysis in aggressive meningioma patients treated with radiosurgery. Larger tumor size predicts poor survival, while nuclear atypia, necrosis, and increased mitotic rate are risk factors for recurrence. Clinical and pathologic predictors may help identify patients that are at higher risk for recurrence.
"The 5-year control rate is equivalent to that of gross-total resection but with lower morbidity. Additionally, adjuvant treatment of subtotally resected tumours results in local control rates equivalent to gross-total resection
[Show abstract][Hide abstract] ABSTRACT: Stereotactic radiosurgery (SRS) is an important treatment option for intracranial lesions. Many studies have shown the effectiveness of photon-SRS for the treatment of skull base (SB) tumours; however, limited data are available for proton-SRS.
Several photon-SRS techniques, including Gamma Knife, modified linear accelerators (Linac) and CyberKnife, have been developed and several studies have compared treatment plan characteristics between protons and photons.
The principles of classical radiobiology are similar for protons and photons even though they differ in terms of physical properties and interaction with matter resulting in different dose distributions.
Protons have special characteristics that allow normal tissues to be spared better than with the use of photons, although their potential clinical superiority remains to be demonstrated.
A critical analysis of the fundamental radiobiological principles, dosimetric characteristics, clinical results, and toxicity of proton- and photon-SRS for SB tumours is provided and discussed with an attempt of defining the advantages and limits of each radiosurgical technique.
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