Long-term evaluation of the effect of hypofractionated high-energy proton treatment of benign meningiomas by means of 11C-l-methionine positron emission tomography

Evolving interest in meningioma, the most common primary brain tumor, has refined contemporary management of these tumors. Problematic, however, is the paucity of prospective clinical trials that provide an evidence-based algorithm for managing meningioma. This review summarizes the published literature regarding the treatment of newly diagnosed and recurrent meningioma, with an emphasis on outcomes stratified by WHO tumor grade. Specifically, this review focuses on patient outcomes following treatment (either adjuvant or at recurrence) with surgery or radiation therapy inclusive of radiosurgery and fractionated radiation therapy. Phase II trials for patients with meningioma have recently completed accrual within the Radiation Therapy Oncology Group and the European Organisation for Research and Treatment of Cancer consortia, and Phase III studies are being developed. However, at present, there are no completed prospective, randomized trials assessing the role of either surgery or radiation therapy. Successful completion of future studies will require a multidisciplinary effort, dissemination of the current knowledge base, improved implementation of WHO grading criteria, standardization of response criteria and other outcome end points, and concerted efforts to address weaknesses in present treatment paradigms, particularly for patients with progressive or recurrent low-grade meningioma or with high-grade meningioma. In parallel efforts, Response Assessment in Neuro-Oncology (RANO) subcommittees are developing a paper on systemic therapies for meningioma and a separate article proposing standardized end point and response criteria for meningioma.

The rates of survival, tumor recurrence, and tumor progression were analyzed in 225 patients with meningioma who underwent surgery as the only treatment modality between 1962 and 1980. Patients were considered to have a recurrence if their studies verified a mass effect in spite of a complete surgical removal, whereas they were defined as having progression if, after a subtotal excision, there was clear radiological documentation of an increase in the size of their tumor. There were 168 females and 57 males (a ratio of 2.9:1), with a peak incidence of tumor occurrence in the fifth (23%), sixth (29%), and seventh (23%) decades of life. Anatomical locations were the convexity (21%), parasagittal area (17%), sphenoid ridge (16%), posterior fossa (14%), parasellar region (12%), olfactory groove (10%), spine (8%), and orbit (2%). The absolute 5-, 10-, and 15-year survival rates were 83%, 77%, and 69%, respectively. Following a total resection, the recurrence-free rate at 5, 10, and 15 years was 93%, 80%, and 68%, respectively, at all sites. In contrast, after a subtotal resection, the progression-free rate was only 63%, 45%, and 9% during the same period (p less than 0.0001). The probability of having a second operation following a total excision after 5, 10, and 15 years was 6%, 15%, and 20%, whereas after a subtotal excision the probability was 25%, 44%, and 84%, respectively (p less than 0.0001). Tumor sites associated with a high percentage of total excisions had a low recurrence/progression rate. For example, 96% of convexity meningiomas were removed in toto, and the recurrence/progression rate at 5 years was only 3%. Parasellar meningiomas, with a 57% total excision rate, had a 5-year probability of recurrence/progression of 19%. Only 28% of sphenoid ridge meningiomas a second resection, the probability of a third operation at 5 and 10 years was 42% and 56%, respectively. There was no difference in the recurrence/progression rates according to the patients' age or sex, or the duration of symptoms. Implications for the potential role of adjunctive medical therapy or radiation therapy for meningiomas are discussed.