Volumetric Analysis of the Growth Rate of Incompletely Resected Intracranial Meningiomas

Mathematical modeling of meningioma volume change after radiation treatment

OBJECTIVE

Meningiomas are the most common primary central nervous tumor and are often treated with radiation therapy. This study examines the long-term volumetric changes of intracranial meningiomas in response to radiation therapy. The objective is to analyze and model the volumetric changes following treatment.

METHODS

Data from a retrospective single-institution database (2005-2015) were used, with inclusion criteria being patients with a diagnosis of meningiomas, along with additional inclusion criteria consisting of treatment with radiation, having at least three magnetic resonance imaging (MRI) scans with one or more before and after radiation treatment, and the patients following up for at least eighteen months. Exclusion criteria consisted of patients less than 18 years old, patients receiving surgery and/or adjuvant chemotherapy following radiation, and patients without any available details regarding radiation treatment parameters. Tumor volumes were measured via T1-weighted post-contrast MRI and calculated using the ABC/2 ellipsoidal approximation, a method allowing for the measurement of non-linear growth volume reduction.

RESULTS

Of 48 meningioma patients considered, 10 % experienced post-radiation growth, while 75 % witnessed a ≥50 % decrease in volume over a follow-up period of 0.3-14.9 years. Median decay rate was 0.81, and within 1.17 years, 90 % achieved the predicted volume reduction. Predicted vs. actual volumes showed a mean difference of 0.009 ± 0.347 cc. Initial tumor volumes strongly correlated (Pearson's R=0.98, R-squared=0.96) with final asymptotic volumes, which had a median of 1.50 cc, with interquartile range (IQR) = [0.39, 3.67].

CONCLUSION

90 % of patients achieved tumor-volume reduction at 1.17 years post-treatment, reaching a non-zero asymptote strongly correlated with initial tumor volume, and 75 % experienced at least a 50 % volume decrease. Individual volume changes for responsive meningiomas can be modeled and predicted using exponential decay curves.

Long-term follow-up in high-grade meningioma and outcome analysis

Objectives

The determinants of progression-free survival (PFS) and overall survival (OS) for higher-grade meningiomas have not been clearly established and to summarize the long-term clinical outcome for patients with grade 2 or 3 meningioma and assess the PFS and OS factors.

Materials and Methods

The study included all individuals, who had undergone surgical removal of cerebral meningiomas between 2005 and 2020 and whose histological results suggested a World Health Organization (WHO) grade 2 or grade 3 diseases. Kaplan-Meier curves are plotted to examine tumor control and OS after the follow-up. The reverse Wald logistic regression and Mantel-Cox test were used in multivariate analysis for tumor recurrence and mortality.

Results

There were 94 individuals enrolled with 82 having WHO grade 2 tumors and 12 having WHO grade 3 lesions. Gross total resection of the tumor was present in 73 patients (78%), and adjuvant radiotherapy (RT) was administered to 43 (45.7%) individuals. During the course of the study, 17 patients died. The WHO grade of the tumor, the extent of resection, and the absence of bone involvement were all independent predictors of better survival in a multivariate analysis. Furthermore, whereas adjuvant RT after surgery enhanced survival, it was not statistically significant (hazard ratios [95% confidence interval CI] = 1.91 [0.15-23.52] [P = 0.61]).

Conclusion

The degree of tumor excision is the strongest predictor of PFS and OS. In the event of a recurrence, rather than opting for upfront radiation, a second surgery with the goal of maximum safe resection should be performed.

Grading meningioma resections: the Simpson classification and beyond

Technological (and also methodological) advances in neurosurgery and neuroimaging have prompted a reappraisal of Simpson's grading of the extent of meningioma resections. To the authors, the published evidence supports the tenets of this classification. Meningioma is an often surgically curable dura-based disease. An extent of meningioma resection classification needs to account for a clinically meaningful variation of the risk of recurrence depending on the aggressiveness of the management of the (dural) tumor origin.Nevertheless, the 1957 Simpson classification undoubtedly suffers from many limitations. Important issues include substantial problems with the applicability of the grading paradigm in different locations. Most notably, tumor location and growth pattern often determine the eventual extent of resection, i.e., the Simpson grading does not reflect what is surgically achievable. Another very significant problem is the inherent subjectivity of relying on individual intraoperative assessments. Neuroimaging advances such as the use of somatostatin receptor PET scanning may help to overcome this central problem. Tumor malignancy and biology in general certainly influence the role of the extent of resection but may not need to be incorporated in an actual extent of resection grading scheme as long as one does not aim at developing a prognostic score. Finally, all attempts at grading meningioma resections use tumor recurrence as the endpoint. However, especially in view of radiosurgery/radiotherapy options, the clinical significance of recurrent tumor growth varies greatly between cases.In summary, while the extent of resection certainly matters in meningioma surgery, grading resections remains controversial. Given the everyday clinical relevance of this issue, a multicenter prospective register or study effort is probably warranted (including a prominent focus on advanced neuroimaging).

Volumetric Growth and Growth Curve Analysis of Residual Intracranial Meningioma

BACKGROUND

After meningioma surgery, approximately 1 in 3 patients will have residual tumor that requires ongoing imaging surveillance. The precise volumetric growth rates of these tumors are unknown.

OBJECTIVE

To identify the volumetric growth rates of residual meningioma, growth trajectory, and factors associated with progression.

METHODS

Patients with residual meningioma identified at a tertiary neurosurgery center between 2004 and 2020 were retrospectively reviewed. Tumor volume was measured using manual segmentation, after surgery and at every follow-up MRI scan. Growth rates were ascertained using a linear mixed-effects model and nonlinear regression analysis of growth trajectories. Progression was defined according to the Response Assessment in Neuro-Oncology (RANO) criteria (40% volume increase).

RESULTS

There were 236 patients with residual meningioma. One hundred and thirty-two patients (56.0%) progressed according to the RANO criteria, with 86 patients being conservatively managed (65.2%) after progression. Thirteen patients (5.5%) developed clinical progression. Over a median follow-up of 5.3 years (interquartile range, 3.5-8.6 years), the absolute growth rate was 0.11 cm 3 per year and the relative growth rate 4.3% per year. Factors associated with residual meningioma progression in multivariable Cox regression analysis were skull base location (hazard ratio [HR] 1.60, 95% CI 1.02-2.50) and increasing Ki-67 index (HR 3.43, 95% CI 1.19-9.90). Most meningioma exhibited exponential and logistic growth patterns (median R 2 value 0.84, 95% CI 0.60-0.90).

CONCLUSION

Absolute and relative growth rates of residual meningioma are low, but most meet the RANO criteria for progression. Location and Ki-67 index can be used to stratify adjuvant treatment and surveillance paradigms.

Sellar masses: diagnosis and treatment

Sellar mases can cause a variety of neuro-ophthalmic manifestations, including compressive optic neuropathy, chiasmal syndrome, and ophthalmoplegia due to cranial nerve palsy. Diagnosis involves a thorough history, neuro-ophthalmic examination, and ancillary tests and investigations. Visual field testing is critical in diagnosing and localizing the lesion and determining the extent of visual field loss. Appropriate neuro-imaging is essential in characterizing and localizing the lesion. Neuro-ophthalmologic assessment include meticulous clinical examination and ancillary tests including,visual field testing, which is useful in localizing the lesion, and optical coherence tomography, which is helpful in assessing the degree of axonal and neuronal loss and predicting the visual outcome. Treatment requires a multidisciplinary approach by different specialties, including radiologists, neuro-ophthalmologists, and neurosurgeons. The two primary treatment modalities for these tumors are surgery and radiation therapy. We review the main types of sellar lesions, their neuro-ophthalmologic evaluation, and treatment options.

Molecular determinants of outcomes in meningiomas

Meningiomas are the most common intracranial primary tumor in adults. Surgery is the predominant therapeutic modality for symptomatic meningiomas. Although the majority of meningiomas are benign, there exists a subset of meningiomas that are clinically aggressive. Recent advances in genetics and epigenetics have uncovered molecular alterations that drive tumor meningioma biology with prognostic and therapeutic implications. In this review, we will discuss the advances on molecular determinants of therapeutic response in meningiomas to date and discuss findings of targeted therapies in meningiomas.

Preoperative Prediction of Intracranial Meningioma Grade Using Conventional CT and MRI

Objective

Preoperative diagnosis of tumor grade can assist in treatment-related decision-making for patients with intracranial meningioma. This study aimed to distinguish between high-grade and low-grade meningiomas using conventional CT and MRI.

Methodology

We retrospectively analyzed 173 consecutive patients with intracranial meningioma (149 low-grade and 24 high-grade tumors) who were treated surgically at the National Hospital Organization Kyushu Medical Center from 2008 to 2020. Clinical and radiological features, including tumor doubling time (Td) and relative growth rate (RGR), were compared between low-grade and high-grade meningiomas.

Results

Multivariate logistic regression analysis showed that symptomatic tumor (p=0.001), non-skull base location (p=0.006), irregular tumor shape (p=0.043), tumor heterogeneity (p=0.025), and peritumoral brain edema (p=0.003) were independent predictors of high-grade meningioma. In 53 patients who underwent surgery because of tumor progression, progression to symptoms (p=0.027), intratumoral heterogeneity (p<0.001), peritumoral brain edema (p=0.001), larger tumor volume (p=0.005), shorter Td (p<0.001), and higher RGR (P<0.001) were significantly associated with high-grade meningioma. Receiver operating characteristics (ROC) curve analysis showed that the optimal Td and annual RGR cut-off values to distinguish high-grade from low-grade meningioma were 460.5 days and 73.2%, respectively (100% sensitivity and 78.6% specificity).

Conclusion

Based on our findings, conventional CT and MRI are useful methods to predict meningioma grades before surgery. High-grade lesions are associated with non-skull base location, irregular tumor shape, intratumoral heterogeneity, and peritumoral brain edema. High-grade meningioma should be suspected in tumors that exhibit Td <460.5 days or annual RGR >73.2% or those that develop intratumoral heterogeneity or surrounding brain edema on surveillance imaging.

Consensus core clinical data elements for meningiomas

BACKGROUND

With increasing molecular analyses of meningiomas, there is a need to harmonize language used to capture clinical data across centers to ensure that molecular alterations are appropriately linked to clinical variables of interest. Here the International Consortium on Meningiomas presents a set of core and supplemental meningioma-specific Common Data Elements (CDEs) to facilitate comparative and pooled analyses.

METHODS

The generation of CDEs followed the four-phase process similar to other National Institute of Neurological Disorders and Stroke (NINDS) CDE projects: discovery, internal validation, external validation, and distribution.

RESULTS

The CDEs were organized into patient- and tumor-level modules. In total, 17 core CDEs (10 patient-level and 7-tumour-level) as well as 14 supplemental CDEs (7 patient-level and 7 tumour-level) were defined and described. These CDEs are now made publicly available for dissemination and adoption.

CONCLUSIONS

CDEs provide a framework for discussion in the neuro-oncology community that will facilitate data sharing for collaborative research projects and aid in developing a common language for comparative and pooled analyses. The meningioma-specific CDEs presented here are intended to be dynamic parameters that evolve with time and The Consortium welcomes international feedback for further refinement and implementation of these CDEs.

Volumetric growth of residual meningioma - A systematic review

Surgical resection of meningioma leaves residual solid tumour in over 25% of patients. Selection for further treatment and follow-up strategy may benefit from knowledge of volumetric growth and factors associated with re-growth. The aim of this review was to evaluate volumetric growth and variables associated with growth in patients that underwent incomplete resection of a meningioma without the use of adjuvant radiotherapy. A systematic review was conducted in accordance with the PRISMA statement and registered a priori with PROSPERO (registration number: CRD42020177052). Six databases were searched up to May 2020. Full text articles analysing volumetric growth rates in at least 10 patients who had residual meningioma after surgery were assessed. Four single-centre, retrospective studies totalling 238 patients were included, of which 99% of meningioma were WHO grade 1. The absolute tumour growth rate ranged from 0.09 to 4.94 cm³ per year. The relative growth rate ranged from 5.11 to 14.18% per year. Varying methods of volumetric assessment and definitions of growth impeded pooled analysis. Pre-operative and residual tumour volume, and hyperintensity on T2 weighted MRI were identified as variables associated with residual meningioma growth, however this was inconsistent across studies. Risk of bias was high in all studies. Radiological regrowth occurred in 42-67% of cases. Our review identified that volumetric growth of residual meningioma is scarcely reported. Sufficiently powered studies are required to delineate volumetric growth and prognostic factors to stratify management.

Intracranial Meningiomas Decrease in Volume on Magnetic Resonance Imaging After Discontinuing Progestin

BACKGROUND

The behavior of meningiomas under influence of progestin therapy remains unclear.

OBJECTIVE

To investigate the relationship between growth kinetics of intracranial meningiomas and usage of the progestin cyproterone acetate (PCA).

METHODS

This study prospectively followed 108 women with 262 intracranial meningiomas and documented PCA use. A per-meningioma analysis was conducted. Changes in meningioma volumes over time, and meningioma growth velocities, were measured on magnetic resonance imaging (MRI) after stopping PCA treatment.

RESULTS

Mean follow-up time was 30 (standard deviation [SD] 29) mo. Ten (4%) meningiomas were treated surgically at presentation. The other 252 meningiomas were followed after stopping PCA treatment. Overall, followed meningiomas decreased their volumes by 33% on average (SD 28%). A total of 188 (72%) meningiomas decreased, 51 (20%) meningiomas remained stable, and 13 (4%) increased in volume of which 3 (1%) were surgically treated because of radiological progression during follow-up after PCA withdrawal. In total, 239 of 262 (91%) meningiomas regressed or stabilized during follow-up. Subgroup analysis in 7 women with 19 meningiomas with follow-up before and after PCA withdrawal demonstrated that meningioma growth velocity changed statistically significantly (P = .02). Meningiomas grew (average velocity of 0.25 mm3/day) while patients were using PCA and shrank (average velocity of -0.54 mm3/day) after discontinuation of PCA.

CONCLUSION

Ninety-one percent of intracranial meningiomas in female patients with long-term PCA use decrease or stabilize on MRI after stopping PCA treatment. Meningioma growth kinetics change significantly from growth during PCA usage to shrinkage after PCA withdrawal.

Long-term outcome of Simpson IV meningioma resection: Would it improve with adjuvant SRS?

OBJECTIVE

Subtotal meningioma resection (STR) is often performed to minimize surgical morbidity. Nevertheless, only a few studies have reported on patient outcome after STR. We studied the long-term outcome of SIV (Simpson grade IV) resection and identified predictive factors of overall survival (OS), progression-free survival (PFS) and time to progression (TTP).

METHODS

A retrospective analysis was performed on 68 patients who underwent SIV resection of meningioma (grade I) from 2004 to 2010. Data were collected from clinical, surgical and pathology records and radiological imaging. Long-term outcomes were evaluated at least 10 years after surgery.

RESULTS

Permanent morbidity was 11.8%, 30-day mortality 2.9% and progression rate 50.0% for a median follow-up duration of 126.6 months. Median TTP was 86.2 months. Adjuvant SRS was the only significant factor associated with longer PFS (p = 0.0052) and TTP (p = 0.0079). Higher age (p = 0.0022), KPS (p = 0.0182), postoperative ECOG score (p = 0.0182) were reliable predictors of shortened OS and aSRS (p = 0.0445) was reliable predictor of longer OS.

CONCLUSION

STR in intracranial meningioma is still viable and often the only treatment option available in high-risk patients or high-risk tumors. Although surgical morbidity and mortality are high, the OS rate was 85.3% at 5 years and 79.4% at 10 years. Because of the considerable progression rate and rather a long term OS the adjuvant SRS should be considered following SIV resection.

Is Contrast Medium Really Needed for Follow-up MRI of Untreated Intracranial Meningiomas?

BACKGROUND AND PURPOSE

Recent concerns relating to tissue deposition of gadolinium are favoring the use of noncontrast MR imaging whenever possible. The purpose of this study was to assess the necessity of gadolinium contrast for follow-up MR imaging of untreated intracranial meningiomas.

MATERIALS AND METHODS

One-hundred twenty-two patients (35 men, 87 women) with meningiomas who underwent brain MR imaging between May 2007 and May 2019 in our institution were included in this retrospective cohort study. We analyzed 132 meningiomas: 73 non-skull base (55%) versus 59 skull base (45%), 93 symptomatic (70%) versus 39 asymptomatic (30%). Fifty-nine meningiomas underwent an operation: 54 World Health Organization grade I (92%) and 5 World Health Organization grade II (8%). All meningiomas were segmented on T1 3D-gadolinium and 2D-T2WI. Agreement between T1 3D-gadolinium and 2D-T2WI segmentations was assessed by the intraclass correlation coefficient.

RESULTS

The mean time between MR images was 1485 days (range, 760-3810 days). There was excellent agreement between T1 3D-gadolinium and T2WI segmentations (P < .001): mean tumor volume (T1 3D-gadolinium: 9012.15 [SD, 19,223.03] mm³; T2WI: 8528.45 [SD, 18,368.18 ] mm³; intraclass correlation coefficient = 0.996), surface area (intraclass correlation coefficient = 0.989), surface/volume ratio (intraclass correlation coefficient = 0.924), maximum 3D diameter (intraclass correlation coefficient = 0.986), maximum 2D diameter in the axial (intraclass correlation coefficient = 0.990), coronal (intraclass correlation coefficient = 0.982), and sagittal planes (intraclass correlation coefficient = 0.985), major axis length (intraclass correlation coefficient = 0.989), minor axis length (intraclass correlation coefficient = 0.992), and least axis length (intraclass correlation coefficient = 0.988). Tumor growth also showed good agreement (P < .001), estimated as a mean of 461.87 [SD, 2704.1] mm³/year on T1 3D-gadolinium and 556.64 [SD, 2624.02 ] mm³/year on T2WI.

CONCLUSIONS

Our results show excellent agreement between the size and growth of meningiomas derived from T1 3D-gadolinium and 2D-T2WI, suggesting that the use of noncontrast MR imaging may be appropriate for the follow-up of untreated meningiomas, which would be cost-effective and avert risks associated with contrast media.

Volumetric growth rate of incidental asymptomatic meningiomas: a single-center prospective cohort study

BACKGROUND

Decision about treatment of incidentally found intracranial meningiomas is controversial and conditioned by the growth potential of these tumors. We aimed to evaluate the growth rate of a cohort of incidentally found asymptomatic meningiomas and to analyze their natural course and the need for eventual treatment.

METHODS

A total of 193 patients harboring intracranial meningiomas (85 with 109 incidental and 108 with 112 symptomatic) were included between 2015 and 2019. In the prospective cohort of incidental meningiomas, we measured size at diagnosis, volumetric growth rate (by segmentation software), appearance of symptoms, and need for surgery or radiotherapy. Progression-free survival and risk factors for growth were assessed with Kaplan-Meier survival and Cox regression analyses.

RESULTS

Among incidental meningiomas, 94/109 (86.2%) remained untreated during a median follow-up of 49.3 months. Tumor growth was observed in 91 (83.5%) and > 15% growth in 40 (36.7%). Neurological symptoms developed in 1 patient (1.2%). Volume increased an average of 0.51 cm³/year (95% CI, 0.20-0.82). Nine patients were operated (9.2%) and 4 underwent radiotherapy (4.7%). Treatment-related complication rates of incidental and symptomatic meningiomas were 0% and 35.4%, respectively. Persistent neurological defects occurred in 46 (40.7%) of symptomatic versus 2 (2.3%) of incidental meningiomas. Among covariates, only brain edema resulted in an increased risk of significant tumor growth in the female subgroup (Cox regression HR 2.96, 95% CI 1.02-8.61, p = 0.046). Size at diagnosis was significantly greater in the symptomatic meningioma group (37.33 cm³ versus 4.74 cm³, p < 0.001).

CONCLUSIONS

Overall, 86% of incidentally found meningiomas remained untreated over the first 4 years of follow-up. The majority grew within the 20% range, yet very few developed symptoms. Treatment-related morbidity was absent in the incidental meningioma group.

The growth rate and clinical outcomes of radiation induced meningioma undergoing treatment or active monitoring

INTRODUCTION

Radiation induced meningioma (RIM) incidence is increasing in line with improved childhood cancer survival. No optimal management strategy consensus exists. This study aimed to delineate meningioma growth rates from tumor discovery and correlate with clinical outcomes.

METHODS

Retrospective study of patients with a RIM, managed at a specialist tertiary neuroscience center (2007-2019). Tumor volume was measured from diagnosis and at subsequent interval scans. Meningioma growth rate was determined using a linear mixed-effects model. Clinical outcomes were correlated with growth rates accounting for imaging and clinical prognostic factors.

RESULTS

Fifty-four patients (110 meningiomas) were included. Median duration of follow-up was 74 months (interquartile range [IQR], 41-102 months). Mean radiation dose was 41 Gy (standard deviation [SD] = 14.9) with a latency period of 34.4 years (SD = 13.7). Median absolute growth rate was 0.62 cm³/year and the median relative growth rate was 72%/year. Forty meningiomas (between 27 patients) underwent surgical intervention after a median follow-up duration of 4 months (IQR 2-35). Operated RIMs were clinically aggressive, likely to be WHO grade 2 at first resection (43.6%) and to progress after surgery (41%). Median time to progression was 28 months (IQR 13-60.5). A larger meningioma at discovery was associated with growth (HR 1.2 [95% CI 1.0-1.5], P = 0.039) but not progression after surgery (HR 2.2 [95% CI 0.7-6.6], P = 0.181). Twenty-seven (50%) patients had multiple meningiomas by the end of the study.

CONCLUSION

RIMs exhibit high absolute and relative growth rates after discovery. Surgery is recommended for symptomatic or rapidly growing meningiomas only. Recurrence risk after surgery is high.

Predictors of recurrence and high growth rate of residual meningiomas after subtotal resection

OBJECTIVE

The extent of resection has been shown to improve outcomes in patients with meningiomas. However, resection can be complicated by constraining local anatomy, leading to subtotal resections. An understanding of the natural history of residual tumors is necessary to better guide postsurgical management and minimize recurrence. This study seeks to identify predictors of recurrence and high growth rate following subtotal resection of intracranial meningiomas.

METHODS

Adult patients who underwent primary surgical resection of a WHO grade I meningioma at a tertiary care institution from 2007-2017 were retrospectively reviewed. Volumetric tumor measurements were made on patients with subtotal resections. Stepwise multivariate proportional hazards regression analyses were performed to identify factors associated with time to recurrence, as well as stepwise multivariate regression analyses to assess for factors associated with high postoperative growth rate.

RESULTS

Of the 141 patients (18%) who underwent radiographic subtotal resection of an intracranial meningioma during the reviewed period, 74 (52%) suffered a recurrence, in which the median (interquartile range, IQR) time to recurrence was 14 (IQR 6-34) months. Among those tumors subtotally resected, the median pre- and postoperative tumor volumes were 17.19 cm3 (IQR 7.47-38.43 cm3) and 2.31 cm3 (IQR 0.98-5.16 cm3), which corresponded to a percentage resection of 82% (IQR 68%-93%). Postoperatively, the median growth rate was 0.09 cm3/year (IQR 0-1.39 cm3/year). Factors associated with recurrence in multivariate analysis included preoperative tumor volume (hazard ratio [HR] 1.008,95% confidence interval [CI] 1.002-1.013, p = 0.008), falcine location (HR 2.215, 95% CI 1.179-4.161, p = 0.021), tentorial location (HR 2.410, 95% CI 1.203-4.829, p = 0.024), and African American race (HR 1.811, 95% CI 1.042-3.146, p = 0.044). Residual volume (RV) was associated with high absolute annual growth rate (odds ratio [OR] 1.175, 95% CI 1.078-1.280, p < 0.0001), with the maximum RV benefit at < 5 cm3 (OR 4.056, 95% CI 1.675-9.822, p = 0.002).

CONCLUSIONS

By identifying predictors of recurrence and growth rate, this study helps identify potential patients with a high chance of recurrence following subtotal resection, which are those with large preoperative tumor volume, falcine location, tentorial location, and African American race. Higher RVs were associated with tumors with higher postoperative growth rates. Recurrences typically occurred 14 months after surgery.

Imaging and diagnostic advances for intracranial meningiomas

The archetypal imaging characteristics of meningiomas are among the most stereotypic of all central nervous system (CNS) tumors. In the era of plain film and ventriculography, imaging was only performed if a mass was suspected, and their results were more suggestive than definitive. Following more than a century of technological development, we can now rely on imaging to non-invasively diagnose meningioma with great confidence and precisely delineate the locations of these tumors relative to their surrounding structures to inform treatment planning. Asymptomatic meningiomas may be identified and their growth monitored over time; moreover, imaging routinely serves as an essential tool to survey tumor burden at various stages during the course of treatment, thereby providing guidance on their effectiveness or the need for further intervention. Modern radiological techniques are expanding the power of imaging from tumor detection and monitoring to include extraction of biologic information from advanced analysis of radiological parameters. These contemporary approaches have led to promising attempts to predict tumor grade and, in turn, contribute prognostic data. In this supplement article, we review important current and future aspects of imaging in the diagnosis and management of meningioma, including conventional and advanced imaging techniques using CT, MRI, and nuclear medicine.

Clinical features of newly developed NF2 intracranial meningiomas through comparative analysis of pediatric and adult patients

OBJECTIVE

NF2 patients can develop new meningiomas throughout their lifetime. Little is known about the clinical features of newly developed NF2 meningiomas. In this study, we analyzed newly developed NF2 meningiomas in a large patient population.

PATIENTS AND METHODS

Among 452 NF2 patients, the location patterns of 81 pediatric and 939 adult NF2 meningiomas were compared to find the predominant locations of newly developed meningiomas in adulthood. The clinical features of 39 newly developed meningiomas in 24 NF2 patients were summarized. Clinical risk factors of NF2 meningioma growth rates were analyzed.

RESULTS

Pediatric patients had significantly more intracranial meningiomas than adult patients at the skull base (except for the petrosal region) (p < 0.0063). Adult patients had significantly more cranial meningiomas than pediatric patients at the parasagittal, parafalcine (middle & posterior), and frontal/parietal/cerebellar convex surfaces (p < 0.0063). Newly developed NF2 meningiomas in adults tended to occur at different locations than the locations of NF2 meningiomas in pediatric patients. New meningiomas could develop at various ages. Ninety-five NF2 patients were imaged and followed up for at least one year. Twenty-four patients (25.3 %) developed 39 new meningiomas during the follow-up period. They usually had initial meningiomas when new meningiomas occurred. The number of newly developed meningiomas per patient and the petrosal location were significantly associated with both the absolute and relative annual growth rates (p < 0.05).

CONCLUSIONS

The number of newly developed NF2 meningiomas seems to be a clinical marker of NF2 disease severity. In adults, new NF2 meningiomas tend to occur in patients with initial meningiomas. The predominant locations of newly developed NF2 meningiomas seem to be the parasagittal, parafalcine (middle/posterior), and frontal/parietal/cerebellar convex surfaces.

Histological Grade of Meningioma: Prediction by Intravoxel Incoherent Motion Histogram Parameters

RATIONALE AND OBJECTIVES

To evaluate the usefulness of intravoxel incoherent motion (IVIM) histogram analysis for differentiating low-grade meningiomas (LGMs) and high-grade meningiomas (HGMs).

MATERIALS AND METHODS

Fifty-nine patients with pathologically confirmed meningiomas (45 LGMs and 14 HGMs) underwent IVIM MR imaging. Maps of IVIM parameters (perfusion fraction, f; true diffusion coefficient, D; and pseudo diffusion coefficient, D*), as well as of the apparent diffusion coefficient (ADC), were generated. Histogram analysis was performed using parametric values from all voxels in regions-of-interest manually drawn to encompass the whole tumor. The histogram results of ADC and IVIM parameters were compared using the Mann-Whitney U test. Area under the receiver operating characteristic curve (AUC) values were generated to evaluate how well each parameter could differentiate LGMs from HGMs. Spearman's rank correlation coefficients were used to evaluate correlations between histogram parameters and Ki-67 expression.

RESULTS

Compared to LGM, HGM showed significantly higher standard deviation (SD), variance, and coefficient of variation (CV) of ADC (p< 0.006-0.028; AUC, 0.693-0.748), D (p< 0.004-0.032; AUC, 0.670-0.752), and significantly higher CV of f (p< 0.005-0.024; AUC = 0.737). Means and percentiles of ADC and IVIM parameters did not differ significantly between LGM and HGM. Significant positive correlations were identified between Ki-67 and histogram parameters of ADC (SD, variance, kurtosis, skewness, and CV) and D (SD, variance, kurtosis, and CV), whereas no significant correlation with Ki-67 was shown for mean or percentiles of ADC and IVIM parameters.

CONCLUSION

Heterogeneity histogram parameters of ADC, D, and f may be useful for differentiating LGMs from HGMs.

Current decision-making in meningiomas

The incidence of meningiomas is rising and the number of incidental cases is increasing steadily. The efficiency and the safety of each treatment strategy are also improving over time. Therefore the indications to treat meningiomas are constantly changing. The aim of meningioma treatment is keeping the patient fully functional while achieving long-term relief or prevention from problems related to intracranial tumor growth. This chapter reviews the natural history and treatment results and aims to put together the information for the most objective decision-making in treating meningiomas. Factors acting on the treatment decision such as anatomical localization, symptomatology, variations in tumor biology, recurrence status, age and co-morbidities, operative gains, and patient preference are individually discussed.

Theragnostic Use of Radiolabelled Dota-Peptides in Meningioma: From Clinical Demand to Future Applications

Meningiomas account for approximately 30% of all new diagnoses of intracranial masses. The 2016 World Health Organization's (WHO) classification currently represents the clinical standard for meningioma's grading and prognostic stratification. However, watchful waiting is frequently the chosen treatment option, although this means the absence of a certain histological diagnosis. Consequently, MRI (or less frequently CT) brain imaging currently represents the unique available tool to define diagnosis, grading, and treatment planning in many cases. Nonetheless, these neuroimaging modalities show some limitations, particularly in the evaluation of skull base lesions. The emerging evidence supporting the use of radiolabelled somatostatin receptor analogues (such as dota-peptides) to provide molecular imaging of meningiomas might at least partially overcome these limitations. Moreover, their potential therapeutic usage might enrich the current clinical offering for these patients. Starting from the strengths and weaknesses of structural and functional neuroimaging in meningiomas, in the present article we systematically reviewed the published studies regarding the use of radiolabelled dota-peptides in surgery and radiotherapy planning, in the restaging of treated patients, as well as in peptide-receptor radionuclide therapy of meningioma.

Volumetric tumor growth rates of meningiomas involving the intracranial venous sinuses

OBJECT

There is currently no consensus as to whether meningiomas located inside the venous sinuses should be aggressively or conservatively treated. The goals of this study were to identify how sinus-invading meningiomas grow, report and compare growth rates of tumor components inside and outside the different venous sinuses, identify risk factors associated with increased tumor growth, and determine the effects of the extent of tumor resection on recurrence for meningiomas that invade the dural venous sinuses.

METHODS

Adult patients who underwent primary, non-biopsy resection of a WHO grade 1 meningioma invading the dural venous sinuses at a tertiary care institution between 2007 and 2015 were retrospectively reviewed. Rates of tumor growth were fit to several growth models to evaluate the most accurate model. Cohen's d analysis was used to identify associations with increased growth of tumor in the venous sinuses. Logistic regression was used to compare extent of resection with recurrence.

RESULTS

Of the 68 patients included in the study, 34 patients had postoperative residual tumors in the venous sinuses that were measured over time. The growth model that best fit the growth of intrasinus meningiomas was the Gompertzian growth model (r² = 0.93). The annual growth rate of meningiomas inside the sinuses was 7.3%, compared to extrasinus tumors with 13.6% growth per year. The only factor significantly associated with increased tumor growth in sinuses was preoperative embolization (effect sizes (ES) [95% CI], 1.874 [7.633-46.735], p = 0.008).

CONCLUSIONS

This study shows that meningiomas involving the venous sinuses have a Gompertzian-type growth with early exponential growth followed by a slower growth rate that plateaus when they reach a certain size. Overall, the growth rate of the intrasinus portion is low (7.3%), which is half of the reported growth rates for other studies involving primarily extrasinus tumors.

Meningioma growth dynamics assessed by radiocarbon retrospective birth dating

It is not known how long it takes from the initial neoplastic transformation of a cell to the detection of a tumor, which would be valuable for understanding tumor growth dynamics. Meningiomas show a broad histological, genetic and clinical spectrum, are usually benign and considered slowly growing. There is an intense debate regarding their age and growth pattern and when meningiomas should be resected. We have assessed the age and growth dynamics of 14 patients with meningiomas (WHO grade I: n = 6 with meningothelial and n = 6 with fibrous subtype, as well as n = 2 atypical WHO grade II meningiomas) by combining retrospective birth-dating of cells by analyzing incorporation of nuclear-bomb-test-derived ¹⁴C, analysis of cell proliferation, cell density, MRI imaging and mathematical modeling. We provide an integrated model of the growth dynamics of benign meningiomas. The mean age of WHO grade I meningiomas was 22.1 ± 6.5 years, whereas atypical WHO grade II meningiomas originated 1.5 ± 0.1 years prior to surgery (p < 0.01). We conclude that WHO grade I meningiomas are very slowly growing brain tumors, which are resected in average two decades after time of origination.

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The age of meningiomas has been difficult to study and is not understood, however age and growth dynamics may affect clinical decision making regarding surgery

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We determined the age and dynamics of meningioma tumor cells using ¹⁴C retrospective birth dating strategy together with MR imaging and histological parameters

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We demonstrate that the average time between initial tumorous cell transformation and detection with resection is 26.3 years in fibrous and years in 17.8 meningothelial meningiomas

Meningiomas are usually benign, slowly growing and frequently occurring brain tumors that are detected incidentally upon imaging or because of causing symptoms. Many tumors remain stable, while others keep growing, why there is a debate whether or not meningiomas need surgical resection upon diagnosis. Specifically, if tumors grow in difficultly accessible brain areas, it would be clinically valuable to predict their age and growth dynamics. The ¹⁴C (radiocarbon) retrospective birth dating technique, an approach taking advantage of the above-ground atomic bomb tests during the Cold War, harbors the unique feature of dating the tumor age, thus providing insights into tumor origination and growth. Using this technique we here establish the age of meningiomas and provide an integrated model – using also MRI and histological parameters – to predict future growth of detected meningiomas, which may help in clinical decision making whether to resect the tumor.

Correlation of volumetric growth and histological grade in 50 meningiomas

INTRODUCTION

Advances in radiological imaging techniques have enabled volumetric measurements of meningiomas to be easily monitored using serial imaging scans. There is limited literature on the relationship between tumour growth rates and the WHO classification of meningiomas despite tumour growth being a major determinant of type and timing of intervention. Volumetric growth has been successfully used to assess growth of low-grade glioma; however, there is limited information on the volumetric growth rate (VGR) of meningiomas. This study aimed to determine the reliability of VGR measurement in patients with meningioma, assess the relationship between VGR and 2016 WHO grading as well as clinical applicability of VGR in monitoring meningioma growth.

METHODS

All histologically proven intracranial meningiomas that underwent resection in a single centre between April 2009 and April 2014 were reviewed and classified according to the 2016 edition of the Classification of the Tumours of the CNS. Only patients who had two pre-operative scans that were at least 3 months apart were included in the study. Two authors performed the volumetric measurements using the Slicer 3D software independently and the inter-rater reliability was assessed. Multiple regression analyses of factors affecting the VGR and VDE of meningiomas were performed using the R statistical software with p < 0.05 considered to be statistically significant.

RESULTS

Of 548 patients who underwent resection of their meningiomas, 66 met the inclusion criteria. Sixteen cases met the exclusion criteria (NF2, spinal location, previous surgical or radiation treatment, significant intra-osseous component and poor quality imaging). Forty-two grade I and 8 grade II meningiomas were included in the analysis. The VGR was significantly higher for grade II meningiomas. Using receiver-operator characteristic (ROC) curve analysis, the optimal threshold that distinguishes between grade I and II meningiomas is 3 cm³/year. Higher histological grade, high initial tumour volume, MRI T2-signal hyperintensity and presence of oedema were found to be significant predictors of higher VGR.

CONCLUSION

Reliable tools now exist to evaluate and monitor volumetric growth of meningiomas. Grade II meningiomas have significantly higher VGR compared with grade I meningiomas and growth of more than 3 cm³/year is strongly suggestive of a higher grade meningioma. A larger, multi-centre prospective study to investigate the applicability of velocity of growth to predict the outcome of patients with meningioma is warranted.

Volumetric growth rates of meningioma and its correlation with histological diagnosis and clinical outcome: a systematic review

INTRODUCTION

Tumour growth has been used to successfully predict progression-free survival in low-grade glioma. This systematic review sought to establish the evidence base regarding the correlation of volumetric growth rates with histological diagnosis and potential to predict clinical outcome in patients with meningioma.

METHODS

This systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Databases were searched for full text English articles analysing volumetric growth rates in patients with a meningioma.

RESULTS

Four retrospective cohort studies were accepted, demonstrating limited evidence of significantly different tumour doubling rates and shapes of growth curves between benign and atypical meningiomas. Heterogeneity of patient characteristics and timing of volumetric assessment, both pre- and post-operatively, limited pooled analysis of the data. No studies performed statistical analysis to demonstrate the clinical utility of growth rates in predicting clinical outcome.

CONCLUSION

This systematic review provides limited evidence in support of the use of volumetric growth rates in meningioma to predict histological diagnosis and clinical outcome to guide future monitoring and treatment.

An Overview of Anterior Skull Base Meningiomas and the Endoscopic Endonasal Approach

Meningiomas represent 30% of all primary brain tumors. Anterior skull base meningiomas represent 8.8% of all meningiomas. Surgical resection is a main treatment option for tumors that are symptomatic and/or growing. Recurrence is directly related to the extent of resection of the tumor, the dural attachment, and pathologic bone. Endoscopic endonasal approaches represent an important addition to the treatment armamentarium for skull base meningiomas. This article provides an overview of meningiomas, with a focus on those of the anterior skull base and their management.

Evolution and future of skull base surgery: the paradigm of skull base meningiomas

BACKGROUND

Skull base meningiomas represent the paradigm for the evolution of skull base surgery within the past 50 years into a distinct neurosurgical subspecialty.

METHODS

From 2005 to 2011, 117 patients with cranial base meningiomas underwent surgical resection. Extent of resection, histologic grade, complications, functional status, and recurrence-free and overall survival data are presented.

RESULTS

The summary rate of gross total resection was 53.0%. The surgical complication and mortality rates were 17.9% and 0.9%, respectively. Five-year recurrence-free survival was 88.0% for grade I meningiomas. A total of 90.3% of patients had a Karnofsky performance score ≥ 80 at last follow-up.

CONCLUSIONS

A large contemporary series of skull base meningiomas is presented. In addition, the evolution of surgical approaches to skull base meningiomas is reviewed, together with the current issues regarding radiation therapy, management of cavernous sinus tumor, oncologic management of atypical and malignant subtypes, molecular genetics, and future therapeutic options.

Treatment of unresectable skull base meningiomas with somatostatin analogs

OBJECT

The standard surgical treatment for meningiomas is total resection, but the complete removal of skull base meningiomas can be difficult for several reasons. Thus, the management of certain meningiomas of the skull base--for example, those involving basal vessels and cranial nerves--remains a challenge. In recent reports it has been suggested that somatostatin (SST) administration can cause growth inhibition of unresectable and recurrent meningiomas. The application of SST and its analogs is not routinely integrated into standard treatment strategies for meningiomas, and clinical studies proving growth-inhibiting effects do not exist. The authors report on their experience using octreotide in patients with recurrent or unresectable meningiomas of the skull base.

METHODS

Between January 1996 and December 2010, 13 patients harboring a progressive residual meningioma (as indicated by MR imaging criteria) following operative therapy were treated with a monthly injection of the SST analog octreotide (Sandostatin LAR [long-acting repeatable] 30 mg, Novartis). Eight of 13 patients had a meningioma of the skull base and were analyzed in the present study. Postoperative tumor enlargement was documented in all patients on MR images obtained before the initiation of SST therapy. All tumors were benign. No patient received radiation or chemotherapy before treatment with SST. The growth of residual tumor was monitored by MR imaging every 12 months.

RESULTS

Three of the 8 patients had undergone surgical treatment once; 3, 2 times; and 2, 3 times. The mean time after the last meningioma operation (before starting SST treatment) and tumor enlargement as indicated by MR imaging criteria was 24 months. A total of 643 monthly cycles of Sandostatin LAR were administered. Five of the 8 patients were on SST continuously and stabilized disease was documented on MR images obtained in these patients during treatment (median 115 months, range 48-180 months). Three of the 8 patients interrupted treatment: after 60 months in 1 case because of tumor progression, after 36 months in 1 case because of side effects, and after 36 months in 1 case because the health insurance company denied cost absorption.

CONCLUSIONS

Although no case of tumor regression was detected on MR imaging, the study results indicated that SST analogs can arrest the progression of unresectable or recurrent benign meningiomas of the skull base in some patients. It remains to be determined whether a controlled prospective clinical trial would be useful.

Growth curve analysis of asymptomatic and symptomatic meningiomas

Meningiomas sometimes appear to stop growing after attaining a large size. Commonly used exponential growth models do not reflect this phenomenon. We attempted to find the best curve to simulate their growth. Fifty-two patients with meningioma were followed up for 3.1-21.7 years (mean 7.5 years) with four or more imaging studies each. Thirty-one patients had asymptomatic tumors. The other 21 patients with residual or recurrent tumor were followed up after surgery. Time-volume curves for each tumor were plotted. Nonlinear regression analyses were performed against power, exponential, logistic, and Gompertzian curves. Time-volume curves corresponded to the Gompertzian and logistic growth curves better than to power or exponential curves. When simulating time-volume curves with Gompertzian curves, the majority of benign meningiomas began to slow their growth before patient age of 80 years. Twenty-three of 31 asymptomatic meningiomas had already passed the inflection point before diagnosis. In contrast, this happened less frequently in symptomatic tumors. Especially, all six atypical meningiomas continued to grow quasi-exponentially. Sigmoid curves that approach a plateau were better descriptors of the growth of benign meningiomas than were curves of unlimited growth. However, atypical meningiomas were unlikely to slow their growth.

Meningioma

Meningiomas are mostly benign tumours originating from the arachnoid cap cells, represent 13-26% of all intracranial tumours. They are more common in older age and in females. Deletion in NF2 gene and exposure to ionizing radiation are established risk factors, while the role of sex hormones is yet not clarified. Five-year survival for typical meningiomas exceeds 80%, but is poorer (5-year survival <60%) in malignant and atypical meningiomas. Papillary and haemangiopericytic morphology, large tumour size, high mitotic index, absence of progesterone receptors, deletions and loss of heterozygosity are poor prognostic factors. Complete surgical excision is the standard treatment. Radiotherapy is currently used in the clinical practice in atypical, malignant or recurrent meningioma at a total dose of 45-60Gy. However, the role of adjuvant irradiation is still controversial and has to be compared in a randomised prospective setting with a policy of watchful waiting. Radiosurgery has gained more and more importance in the management of meningiomas, especially in meningiomas that cannot be completely resected as for many skull base meningiomas. Medical therapy for patients with recurrent, progressive and symptomatic disease after repeated surgery, radiosurgery and radiotherapy is investigational. Hormonal therapy with progesterone antagonists has shown modest results, while chemotherapy with hydroxyurea appears moderately active.