Different responses of benign and atypical meningiomas to gamma-knife radiosurgery: report of two cases with immunohistochemical analysis

Predict Treatment Response by Magnetic Resonance Diffusion Weighted Imaging: A Preliminary Study on 46 Meningiomas Treated with Proton-Therapy

Objective: a considerable subgroup of meningiomas (MN) exhibit indolent and insidious growth. Strategies to detect earlier treatment responses based on tumour biology rather than on size can be useful. We aimed to characterize therapy-induced changes in the apparent diffusion coefficient (ADC) of MN treated with proton-therapy (PT), determining whether the pre- and early post-treatment ADC values may predict tumour response. Methods: Forty-four subjects with MN treated with PT were retrospectively enrolled. All patients underwent conventional magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) at baseline and each 3 months for a follow-up period up to 36 months after the beginning of PT. Mean relative ADC (rADCm) values of 46 MN were measured at each exam. The volume variation percentage (VV) for each MN was calculated. The Wilcoxon test was used to assess the differences in rADCm values between pre-treatment and post-treatment exams. Patients were grouped in terms of VV (threshold −20%). A p < 0.05 was considered statistically significant for all the tests. Results: A significant progressive increase of rADCm values was detected at each time point when compared to baseline rADCm (p < 0.05). Subjects that showed higher pre-treatment rADCm values had no significant volume changes or showed volume increase, while subjects that showed a VV < −20% had significantly lower pre-treatment rADCm values. Higher and earlier rADCm increases (3 months) are related to greater volume reduction. Conclusion: In MN treated with PT, pre-treatment rADCm values and longitudinal rADCm changes may predict treatment response.

Patterns of skull base meningioma progression after failed radiosurgery

Object

Stereotactic radiosurgery has been reported to be an effective alternative to surgical removal of small to medium benign meningiomas as well as an adjuvant treatment modality to reduce the risk of tumor progression after subtotal resection. Its efficacy has been proved by excellent short-term radiosurgically demonstrated control rates, which have been reported to approach or exceed 90% in many contemporary studies involving the use of either linear accelerator–based systems or the Gamma Knife. Little is known, however, regarding the growth patterns of meningiomas that fail to stabilize after radiosurgery.

Methods

The authors report 13 cases of benign skull base meningiomas (World Health Organization Grade I) that demonstrated progression after radiosurgical treatment as a primary or an adjuvant therapy. Several tumors demonstrated rapid growth immediately after radiosurgical treatment, whereas other lesions progressed in a very delayed manner in some patients (up to 14 years after treatment). Regardless of the interval after which it occurs, tumor growth can be quite aggressive once it has begun.

Conclusions

Skull base meningioma growth can be aggressive after failed radiosurgery in some patients, and treatment failure can occur at long intervals following treatment. Special attention must be devoted to such significant occurrences given the increasing number of patients undergoing stereotactic radiosurgery for benign tumors, and careful extended (> 10 years) follow up must be undertaken in all patients after radiosurgery.