Treatment of intracranial meningioma with single-session and fractionated radiosurgery: a propensity score matching study

Intracranial meningiomas: an update of the 2021 World Health Organization classifications and review of management with a focus on radiation therapy

Meningiomas account for approximately one third of all primary intracranial tumors. Arising from the cells of the arachnoid mater, these neoplasms are found along meningeal surfaces within the calvarium and spinal canal. Many are discovered incidentally, and most are idiopathic, although risk factors associated with meningioma development include age, sex, prior radiation exposure, and familial genetic diseases. The World Health Organization grading system is based on histologic criteria, and are as follows: grade 1 meningiomas, a benign subtype; grade 2 meningiomas, which are of intermediately aggressive behavior and usually manifest histologic atypia; and grade 3, which demonstrate aggressive malignant behavior. Management is heavily dependent on tumor location, grade, and symptomatology. While many imaging-defined low grade appearing meningiomas are suitable for observation with serial imaging, others require aggressive management with surgery and adjuvant radiotherapy. For patients needing intervention, surgery is the optimal definitive approach with adjuvant radiation therapy guided by extent of resection, tumor grade, and location in addition to patient specific factors such as life expectancy. For grade 1 lesions, radiation can also be used as a monotherapy in the form of stereotactic radiosurgery or standard fractionated radiation therapy depending on tumor size, anatomic location, and proximity to dose-limiting organs at risk. Optimal management is paramount because of the generally long life-expectancy of patients with meningioma and the morbidity that can arise from tumor growth and recurrence as well as therapy itself.

The role of radiation therapy and systemic treatments in meningioma: The present and the future

Meningiomas are the most prevalent tumors of the central nervous system. Their standard treatment is surgery, which can be curative. Adjuvant radiotherapy treatment is reserved for newly diagnosed cases of grade II and grade III meningiomas in cases of recurrent disease or when surgery is not radical or feasible. However, around 20% of these patients cannot undergo further surgical and/or radiotherapy treatment. Systemic oncological therapy can find its place in this setting. Several tyrosine kinase inhibitors have been tested (gefitinib, erlotinib, sunitinib) with unsatisfactory or negative results. Bevacizumab has shown encouraging results in these settings of patients. Immunotherapy with immune checkpoint inhibitors has reported interesting results with modest objective response rates. Several ongoing studies are assessing different target therapies and multimodal therapies; the results are to be disclosed. Not only a better understanding of the molecular characteristics in meningiomas has allowed the gathering of more information regarding pathogenesis and prognosis, but in addition, the availability of new target therapy, immunotherapy, and biological drugs has widened the scope of potentially effective treatments in this patient population. The aim of this review was to explore the radiotherapy and systemic treatments of meningioma with an analysis of ongoing trials and future therapeutic perspectives.

Correlation between initial tumor enlargement and magnetic resonance imaging characteristics following linear accelerator-based stereotactic radiosurgery for acoustic neuromas

BACKGROUND

Initial tumor enlargement (or pseudoprogression) instead of true tumor progression is a common phenomenon in patients with acoustic neuromas who are treated with stereotactic radiosurgery (SRS). This phenomenon can affect clinical decision-making and patient management. This study assessed the correlation between initial tumor enlargement and magnetic resonance imaging characteristics in patients with acoustic neuromas who were treated with linear accelerator (LINAC)-based SRS. The long-term tumor control outcomes were also analyzed.

MATERIALS AND METHODS

In total, 330 patients with sporadic acoustic neuromas who were treated with LINAC SRS between March 2006 and March 2020 were retrospectively evaluated to assess their initial tumor enlargement. The tumors were divided into homogeneously enhanced, heterogeneously enhanced, and cystic types based on the morphological characteristics noted on magnetic resonance images. Tumor control was assessed in 275 patients with a follow-up duration of more than 2 years.

RESULTS

Initial enlargement was observed in 137 of 330 (41.5%) tumors as early as 3 months after LINAC SRS. Data analysis revealed that postoperative tumors with a residual volume lower than 2.5 cm3 had a lower incidence of initial enlargement (p = 0.039). No correlation was noted between the initial enlargement and morphological characteristics of tumors. In patients with a mean follow-up duration of 82.8 ± 37.2 months, heterogeneously enhanced tumors exhibited a lower control rate than homogeneously enhanced and cystic tumors (p = 0.045). No correlation was noted between initial enlargement and tumor control.

CONCLUSION

Initial enlargement can occur as early as 3 months after SRS. Postoperative residual tumors with a volume lower than 2.5 cm3 exhibit a lower incidence of initial enlargement. Heterogeneously enhanced tumors have a lower local control rate.

Incidental Meningiomas: Potential Predictors of Growth and Current State of Management

The rise in availability of neuroimaging has led to an increase in incidentally discovered meningiomas. These tumors are typically asymptomatic and tend to display slow growth. Treatment options include observation with serial monitoring, radiation, and surgery. Although optimal management is unclear, clinicians recommend a conservative approach, which preserves quality of life and limits unnecessary intervention. Several risk factors have been investigated for their potential utility in the development of prognostic models for risk assessment. Herein, the authors review the current literature on incidental meningiomas, focusing their discussion on potential predictive factors for tumor growth and appropriate management practices.

Hypofractionated Radiosurgery for Large or in Critical-Site Intracranial Meningioma: Results of a Phase 2 Prospective Study

PURPOSE

Radiosurgery is a well-known, safe, and effective technique used in the treatment of intracranial meningiomas. However, single-fraction radiosurgery can lead to high toxicity rates when large-volume or critically located lesions are targeted. Multisession-also called hypofractionated-radiosurgery (hypo-RS) might overcome these limitations. Accordingly, we carried out a prospective phase 2 trial, aiming to establish whether a fractionated RS schedule of 25 Gy in 5 fractions would be safe and effective in treating large (≥ 3 cm) and/or critically located (<3 mm from critical structures) grade 1 intracranial meningiomas. The main aim was to evaluate the safety of hypo-RS in terms of absence of adverse events. The secondary aim was to evaluate tumor response in terms of local control, defined as stability or reduction of lesion volume.

METHODS AND MATERIALS

We prospectively enrolled patients with diagnoses of grade 1 meningiomas, large size and/or critically located lesions, either histologically diagnosed or imaging defined. Additional inclusion criteria were signed informed consent, an age of ≥18 years, and Karnofsky Performance Status ≥70.

RESULTS

Between 2011 and 2016, 178 patients were consecutively enrolled. The median follow-up was 53 months (range, 4-101 months). Overall, the toxicity rate was 12.7% (21 of 166 patients). At a 5-year minimum follow-up, the patients' toxicity rates were 11.7 % (9 of 77 patients). Symptom evaluation at both 3-year and last follow-up showed an improvement in most of the patients. Five-year local tumor control was 97% (95% confidence interval, 92%-99%).

CONCLUSIONS

Hypo-RS schedule of 25 Gy in 5 fractions is a well-tolerated option in the treatment of large-volume and/or critically located benign meningiomas. Early results suggest favorable local control, although longer-term follow-up is needed.

Risk factors for peritumoral edema after radiosurgery for intracranial benign meningiomas: a long-term follow-up in a single institution

OBJECTIVE

Peritumoral edema (PTE) is recognized as a complication following stereotactic radiosurgery (SRS). The aim of this paper was to evaluate the risk of post-SRS PTE for intracranial benign meningiomas and determine the predictive factors.

METHODS

Between 2006 and 2021, 227 patients with 237 WHO grade I meningiomas were treated with Novalis linear accelerator SRS. All patients were treated with a single-fraction dose of 11–20 Gy (median 14 Gy). The median tumor volume was 3.32 cm3 (range 0.24–51.7 cm3).

RESULTS

The median follow-up was 52 months (range 12–178 months). The actuarial local tumor control rates at 2, 5, and 10 years after SRS were 99.0%, 96.7%, and 86.3%, respectively. Twenty-seven (11.9%) patients developed new or worsened post-SRS PTE, with a median onset time of 5.2 months (range 1.2–50 months). Only 2 patients developed post-SRS PTE after 24 months. The authors evaluated factors related to new-onset or worsened PTE after SRS. In univariate analysis, initial tumor volume > 10 cm3 (p = 0.03), total marginal dose > 14 Gy (p < 0.001), preexisting edema (p < 0.0001), tumor location (p < 0.001), parasagittal location (p < 0.0001), superior sagittal sinus (SSS) involvement (p < 0.0001), and SSS invasion (p < 0.015) were found to be significant risk factors. In multivariate analysis, total marginal dose > 14 Gy (HR 3.38, 95% CI 1.37–8.33, p = 0.008), preexisting SRS edema (HR 12.86, 95% CI 1.09–4.15, p < 0.0001), tumor location (HR 2.13, 95% CI 1.04–3.72, p = 0.027), parasagittal location (HR 8.84, 95% CI 1.48–52.76, p = 0.017), and SSS invasion (HR 0.34, 95% CI 0.13–0.89, p = 0.027) were significant risk factors. Twelve (5.3%) patients were symptomatic. Ten of 27 patients had complete resolution of neurological symptoms and edema improvement with steroid treatment. Steroid treatment failed in 2 patients, who subsequently required resection for PTE.

CONCLUSIONS

Radiosurgery is a safe and effective method of treating benign intracranial meningiomas according to long-term follow-up. We also identified total marginal dose > 14 Gy, preexisting PTE, parasagittal location, and SSS invasion as predictors of post-SRS PTE. Risk factors for post-SRS PTE should be considered in meningioma treatment.

Identification and Management of Aggressive Meningiomas

Meningiomas are common primary central nervous system tumors derived from the meninges, with management most frequently entailing serial monitoring or a combination of surgery and/or radiation therapy. Although often considered benign lesions, meningiomas can not only be surgically inaccessible but also exhibit aggressive growth and recurrence. In such cases, adjuvant radiation and systemic therapy may be required for tumor control. In this review, we briefly describe the current WHO grading scale for meningioma and provide demonstrative cases of treatment-resistant meningiomas. We also summarize frequently observed molecular abnormalities and their correlation with intracranial location and recurrence rate. We then describe how genetic and epigenetic features might supplement or even replace histopathologic features for improved identification of aggressive lesions. Finally, we describe the role of surgery, radiotherapy, and ongoing systemic therapy as well as precision medicine clinical trials for the treatment of recurrent meningioma.

Radiotherapy of benign intracranial tumours

We present the updated recommendations of the French Society for Radiation Oncology on benign intracranial tumours. Most of them are meningiomas, vestibular schwannomas, pituitary adenomas, craniopharyngiomas, and glomus tumours. Some grow very slowly, and can be observed without specific treatment, especially if they are asymptomatic. Symptomatic or growing tumours are treated by surgery, which is the reference treatment. When surgery is not possible, due to the location of the lesion, or general conditions, radiotherapy can be applied, as it is if there is a postoperative growing residual tumour, or a local relapse. Indications have to be discussed at a multidisciplinary panel, with precise evaluation of the benefit and risks of the treatments. The techniques to be used are the most modern ones, as multimodal imaging and image-guided radiation therapy. Stereotactic treatments, using fractionated or single doses depending on the size or the location of the tumours, are commonly realized, to avoid as much a possible the occurrence of late side effects.