Cytogenetic study of six cases of radiation-induced meningiomas

How safe and effective is irradiating radiation-induced meningiomas? Single-center experience in primary and salvage Gamma-Knife Radiosurgery, systematic review, and metanalysis of current evidence on the topic

This is a single-center experience and metanalysis of the safety and efficacy measures of Gamma-knife stereotactic radiosurgery (SRS-GK) for radiation-induced meningiomas (RIMs). This study comprised a single-center analysis of SRS-GK for RIMs at IRCCS San Raffaele Hospital, Milan, Italy, and a systematic literature review and meta-analysis to address the actuarial local control (LC), distant control (DC), progression-free survival (PFS), and toxicity. The original series comprised 13 patients harboring 30 RIMs. Partial response was observed in 26 %, stability in 52 %, and progression in 22 %. The 5-year LC and DC rates were 71 % and 67 %. One patient developed radionecrosis, and an additional 2 presented edema. Metanalysis comprised 4 papers and data from the original series, comprising 146 patients and 308 RIMs. The 5-year LC was 84 %, the DC 67 %, and radionecrosis in 1.4 %. SRS-GK has an efficacy profile falling between that observed for radiologically suspected sporadic meningiomas and confirmed higher-grade lesions.

Outcomes of radiation-induced meningiomas treated with stereotactic radiosurgery

PURPOSE

Data on the efficacy and safety of stereotactic radiosurgery (SRS) for treatment of radiation-induced meningiomas (RIMs) are limited.

METHODS

A single institution database of Cobalt-60 SRS cases from 08/1999 to 10/2020 was reviewed. Radiation-induced meningiomas were identified using Cahan's criteria. Endpoints included overall survival (OS), progression free survival (PFS), local control (LC), treatment failure, and treatment toxicity. Univariate and multivariate analyses were performed using cox proportional hazard models.

RESULTS

A total of 29 patients with 86 RIM lesions were identified. Median follow-up after SRS was 59 months. The median dose prescribed to the 50% isodose line was 14 Gy (range 12-20 Gy). The actuarial 5-yr OS and PFS were 96% and 68%, respectively. Patients treated for recurrent RIMs had a significantly lower PFS (45% vs 94% at 3 yr, p < 0.005) than patients treated in the upfront setting. Patients with presumed or WHO grade I RIMs had a significantly greater PFS (3-year PFS 96% vs 20%) than patients with WHO grade II RIMs (p < 0.005). On a per-lesion basis, local control (LC) at 1-, 3-, and 5-yrs was 82%, 76%, 74%, respectively. On multivariate analysis, female gender was associated with improved LC (p < 0.001), while marginal doses > 14 Gy were associated with worse local control (p < 0.001). Grade I-III toxicity following treatment was 9.0%.

CONCLUSIONS

Stereotactic radiosurgery is a safe and effective treatment option for radiographic RIMs, WHO grade I RIMs, or lesions treated in the upfront setting. WHO grade II lesions and recurrent lesions are at increased risk for disease progression.

Radiation-induced meningiomas

Radiation-induced meningiomas (RIMs) became more common as the use of ionizing radiation was adopted in the treatment of medical conditions, both benign and malignant. Currently, RIMs represent the most common radiation-induced tumors. They are heterogeneous in terms of patient characteristics, radiographic appearance, genetics, pathology, symptoms, and management strategies. They tend to occur in a younger population and are generally more aggressive in nature than their spontaneous counterparts. Their characteristics also vary based on the dose of radiation received, which is most commonly separated into low dose (<10Gy) and high dose (>10Gy). The importance of the dosing classification is that it can provide insight into the nature and biologic behavior of the tumor. Given their heterogeneity, RIMs pose significant challenges in management. While surgical resection remains the preferred treatment when feasible, recent data supports stereotactic radiosurgery (SRS) as a comparable alternative. Although there is more knowledge about the molecular pathways leading to RIMs, targeted drug therapy is still limited and is the focus of current research.

High-grade meningiomas: biology and implications

The epochal developments in the treatment of meningioma—microsurgery, skull base techniques, and radiation therapy—will be appended to include the rational application of targeted and immune therapeutics, previously ill-fitting concepts for a tumor that has traditionally been a regarded as a surgical disease. The genomic and immunological architecture of these tumors continues to be defined in ever-greater detail. Grade I meningiomas are driven by NF2 alterations or mutations in AKT1, SMO, TRAF7, PIK3CA, KLF4, POLR2A, SUFU, and SMARCB1. Higher-grade tumors, however, are driven nearly exclusively by NF2/chr22 loss and are marked by infrequent targetable mutations, although they may harbor a greater mutation burden overall. TERT mutations may be more common in tumors that progress in histological grade; SMARCE1 alteration has become a signature of the clear cell subtype; and BAP1 in rhabdoid variants may confer sensitivity to pharmacological inhibition. Compared with grade I meningiomas, the most prominent alteration in grade II and III meningiomas is a significant increase in chromosomal gains and losses, or copy number alterations, which may have behavioral implications. Furthermore, integrated genomic analyses suggest phenotypic subgrouping by methylation profile and a specific role for PRC2 complex activation. Lastly, there exists a complex phylogenetic relationship among recurrent high-grade tumors, which continues to underscore a role for the most traditional therapy in our arsenal: surgery.

Therapeutic radiation for childhood cancer drives structural aberrations of NF2 in meningiomas

Cranial radiotherapy improves survival of the most common childhood cancers, including brain tumors and leukemia. Unfortunately, long-term survivors are faced with consequences of secondary neoplasia, including radiation-induced meningiomas (RIMs). We characterized 31 RIMs with exome/NF2 intronic sequencing, RNA sequencing and methylation profiling, and found NF2 gene rearrangements in 12/31 of RIMs, an observation previously unreported in sporadic meningioma (SM). Additionally, known recurrent mutations characteristic of SM, including AKT1, KLF4, TRAF7 and SMO, were not observed in RIMs. Combined losses of chromosomes 1p and 22q were common in RIMs (16/18 cases) and overall, chromosomal aberrations were more complex than that observed in SM. Patterns of DNA methylation profiling supported similar cell of origin between RIMs and SMs. The findings indicate that the mutational landscape of RIMs is distinct from SMs, and have significant therapeutic implications for survivors of childhood cranial radiation and the elucidation of the molecular pathogenesis of meningiomas.

Radiation-induced meningiomas are often more aggressive than sporadic ones. In this study, the authors perform an exome, methylation and RNA-seq analysis of 31 cases of radiation-induced meningioma and show NF2 rearrangement, an observation previously unreported in the sporadic tumors.

Double trouble: a tale of two radio-treatments

In recent years, an increasing number of patients are treated with radiation. In the early era of radiotherapy, which began soon after X-rays were discovered by Roentgen in 1895, tumours were irradiated with high doses of X-rays in a single fraction. The major initial setback was the damage caused to normal tissues; however, in recent times the use of stereotactic radiosurgery, which delivers high doses of radiation precisely to abnormal tissue targets while sparing the surrounding normal brain tissue, and particularly for surgically inaccessible tumours, has taken centre stage. Prophylactic whole brain radiation (in conjunction with aggressive chemotherapy) for childhood acute lymphoblastic leukaemia has been shown to improve patient survival, however, this is associated with complications in survivors. We report an interesting case of one of the longest survivors who has had double complications from radiotherapy-based interventions.

Pathology and genetics of meningiomas

This article constitutes a mini-review of the pathology and genetics of meningiomas. Meningiomas are the most common primary intracranial tumors. They are usually durally based and are often found adjacent to venous sinuses and dural infoldings. The majority of these tumors are WHO grade I, although a minority is WHO grade II, atypical, or WHO grade III, anaplastic. Grade II and III meningiomas show a greater tendency than Grade I tumors to recur and metastasize. The current WHO scheme recognizes 15 histologic subtypes of meningiomas. Nine of these are WHO grade I, three are grade II, and three are grade III. In addition to these histologic subtypes, meningiomas can also be graded on the basis of mitotic activity, evidence of brain invasion, growth pattern cellular density, nuclear atypia, and necrosis. Loss of the long arm of chromosome 22, which is usually associated with inactivation of the NF2 gene, is the most common genetic abnormality found in meningiomas. Other chromosomal abnormalities associated with tumorogenesis and increased gradeof meningiomas include loss of heterozygosity for chromosome 1p, loss of 14q, deletion of 9p21, abnormalities of chromosome 10 and 17q. Telomerase activity increases with meningiomas grade as well. The only proven environmental risk factor for meningiomas is ionizing radiation. Radiation-induced meningiomas are more often multiple and have higher recurrence rates than standard meningiomas.

STEREOTACTIC RADIOSURGERY FOR RADIATION-INDUCED MENINGIOMAS

OBJECTIVE

Radiation-induced meningiomas of the brain are typically managed with surgical resection. Stereotactic radiosurgery (SRS) has become an important primary or adjuvant management for patients with intracranial meningiomas, but the value of this approach for radiation-induced tumors is unclear.

METHODS

This series consisted of 19 patients (mean age, 40 years) with 24 tumors. The patients met criteria for a radiation-induced meningioma and underwent gamma knife radiosurgery. Seven patients had undergone a previous resection. The World Health Organization tumor grades for those with prior histology were Grade I (n = 5) and Grade II (n = 2). The median tumor volume was 4.4 cm3. Radiosurgery was performed using a median margin dose of 13 Gy.

RESULTS

Serial imaging was evaluated in all patients at a median follow-up of 44 months. The control rate was 75% after primary radiosurgery. Delayed resection after radiosurgery was performed in 5 patients (26%) at an average of 39 months. The median latency between radiation therapy for original disease and SRS for radiation-induced meningiomas was 29.7 years (range, 7.3–59.0 years). The overall survival after SRS was 94.1% and 80.7% at 3 and 5 years, respectively. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 5.3% (1 optic neuropathy). Asymptomatic peritumoral imaging changes compatible with an adverse radiation effect developed in 1 patient.

CONCLUSION

SRS provides satisfactory control rates either after resection or as an alternative to resection. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection.

Molecular genetics of meningiomas: from basic research to potential clinical applications

To review our current understanding of the molecular pathogenesis of meningiomas, to suggest topics for future investigations, and to present perspectives for clinical application. Significant progress has been made in recent years in delineating the molecular mechanisms involved in meningioma formation, growth, and malignant progression. However, many questions remain unanswered. Mutations in the NF2 gene probably account for the formation of more than half of all meningiomas. On the other hand, the molecular events underlying the initiation of meningiomas without NF2 mutations have yet to be identified. Investigating hereditary conditions associated with an increased meningioma incidence and the mechanisms underlying the development of radiation-induced meningiomas could potentially yield relevant insights. Meningioma growth is sustained by the dysregulated expression of steroid hormones, growth factors, their receptors, and activation of signal transduction cascades. The underlying genetic causes are unknown. Malignant progression of meningiomas probably involves the inactivation of tumor suppressor genes on chromosomes 1p, 9p, 10q, and 14q. However, with the possible exception of INK4A/INK4B, the actual targets of these chromosomal losses have remained largely elusive. Cell cycle dysregulation and telomerase activation have been recognized as important steps in meningioma progression. Telomere dynamics, cell cycle control, and the mechanisms responsible for deoxyribonucleic acid damage control are tightly interwoven. Investigating genes involved in the maintenance of genomic integrity might significantly deepen the understanding of meningioma progression. An area that has received relatively little attention thus far is the genetic background of meningioma spread and invasion. Possible clinical applications of the molecular data available may include a meningioma grading system based on genetic alterations, as well as therapeutic strategies for refractory meningiomas aimed at interfering with signal transduction pathways.

Meningeal tumors of childhood and infancy. An update and literature review

Meningeal derived tumors of the first 2 decades of life are often diagnostically challenging due to the wide morphologic spectrum encountered and the rarity of most individual entities. The 2 most common patterns include the dural/leptomeningeal-based mass and neoplastic meningitis. Both primary and secondary meningeal presentations may occur, either early or late in the course of various meningothelial, mesenchymal, embryonal, glial, hematopoietic, histiocytic, melanocytic, and inflammatory tumors. As in other areas of pediatric pathology, there are significant differences between this patient cohort and adults, differences which will be emphasized in this review.

Cancer therapy-associated CNS neuropathology: an update and review of the literature

Standard therapeutic options for brain tumors include surgery, radiation, and chemotherapy. Unfortunately, these same therapies pose risks of neurotoxicity, the most common long-term complications being radiation necrosis, chemotherapy-associated leukoencephalopathy, and secondary neoplasms. These side effects remain difficult to predict, but are associated with risk factors that include patient age, therapeutic modality and dosage, genetic background, and idiosyncratic predispositions. Experimental treatments designed to enhance efficacy and to minimize neurotoxicity include molecularly targeted, genetic, stem cell, and immune therapies. Newer modifications in radiation and drug delivery include stereotactic radiosurgery, interstitial therapy such as intracavitary brachytherapy and gliadel wafer placement, 3D conformal radiation, boron neutron capture therapy, radiosensitizers, blood-brain barrier disrupting agents, and convection enhanced delivery. Toxicities associated with these newer modalities have yet to be fully investigated and documented. Additionally, a number of recently implemented radiographic techniques such as PET and SPECT imaging have enhanced the ability to distinguish recurrent tumor from radiation necrosis. Nevertheless, post-therapeutic brain biopsies and autopsies remain the gold standard for assessing neurotoxicity, therapeutic efficacy, tumor progression, and the development of secondary neoplasms. At the same time, treatment-associated changes such as tumor necrosis, vasculopathy, inflammation, and cytologic atypia can pose significant diagnostic pitfalls, particularly if the pathologist is not provided a detailed therapeutic history. Therefore, it is critical to recognize the full spectrum of cancer therapy-associated neuropathology, the topic of the current review.

The Burden of Radiation-Induced Central Nervous System Tumors

Radiation-induced tumors of the central and peripheral nervous systems are becoming a noticeable subset of tumors seen at referral institutions. This paper outlines a single institution s experience with 22 examples of secondary meningiomas, gliomas, and sarcomas that developed in adults. These tumors are being increasingly encountered by physicians, but the greatest burden is on the patients themselves, who not only experience the life-altering effects of the original tumor and the subsequent delayed cognitive effects of radiotherapy, but later develop a second intracranial neoplasm. We detail a particularly poignant example of a 34-year-old man who developed a high-grade sarcoma with rhabdomyosarcomatous and osteogenic elements. Local control was difficult over the next year, and he eventually developed cerebrospinal fluid dissemination and succumbed. Although radiation-induced neoplasm remain relatively infrequent numerically, each case reminds us of the need for new, less toxic, and more targeted therapies for brain neoplasms.

Molecular genetics of meningiomas

In this article the authors provide a brief description of the current understanding of meningioma genetics. Chromosome 22 abnormalities, especially in the Neurofibromatosis Type 2 (NF2) gene, have been associated with meningioma development. Loss of heterozygosity of chromosome 22 occurs in approximately 60% of meningiomas; however, loss of NF2 gene function occurs in only one third of these lesions. This discrepancy supports the theory that a second tumor suppressor gene exists on chromosome 22, and the authors introduce several possible gene candidates, including BAM22, LARGE, INI1, and MN1 genes. Deletions of 1p have also been shown to correlate with meningioma progression. The genetic similarities and differences among sporadic, NF2-associated, pediatric, and radiation-induced meningiomas are discussed, with the observation that the nonsporadic meningiomas have a higher incidence of multiple chromosomal abnormalities at presentation. Ultimately, a better understanding of the molecular pathways of meningioma tumorigenesis will lead to new, successful treatments.

Molecular pathogenesis of meningiomas

Meningiomas are common central nervous system tumors that originate from the meningeal coverings of the brain and the spinal cord. Most meningiomas are slowly growing benign tumors that histologically correspond to World Health Organization (WHO) grade I. However, certain rare histological variants (clear cell, chordoid, papillary, and rhabdoid), as well as atypical (WHO grade II) and anaplastic (WHO grade III) meningiomas show a more aggressive biological behavior and are clinically associated with a high risk of local recurrence and a less favorable prognosis. This review summarizes the most important features of meningioma pathology and provides an up-to-date overview about the molecular mechanisms involved in meningioma initiation and progression. Current data indicate that meningioma initiation is closely linked to the inactivation of one or more members of the highly conserved protein 4.1 superfamily, including the neurofibromatosis type 2 gene product merlin/schwannomin, protein 4.IB (DAL-1) and protein 4.1R. The genetic alterations in atypical meningiomas are complex and involve losses on 1p, 6q, 10, 14q and 18q, as well as gains on multiple chromosomes. The relevant genes are still unknown. Anaplastic meningiomas show even more complex genetic alterations, including frequent alteration of the CDKN2A, p14ARF, and CDKN2B tumor suppressor genes at 9p21, as well as gene amplification on 17q23. A better understanding of the molecular mechanisms involved in meningioma pathogenesis may not only lead to the identification of novel diagnostic and prognostic marker but will also facilitate the development of new pathogenesis-based therapeutic strategies.

Radiation-induced intracranial meningiomas: review of six operated cases

It is well known that radiation can induce meningiomas. These tumors usually arise in patients with a history of low-dose radiation to the scalp for treatment of tinea capitis or high-dose radiation for a previous brain tumor. Radiation-associated meningiomas (RAMs) morphologically resemble their spontaneously arising counterparts. However, RAMs frequently present a more malignant phenotype and, as such, are diagnosed as "atypical" or "aggressive" meningiomas and occur predominantly in younger patients. This paper describes six cases of radiation-associated intracranial meningiomas in patients previously treated with low-dose radiation to the scalp for tinea capitis.

Radiation-induced meningiomas: clinical, pathological, cytokinetic, and cytogenetic characteristics

Object. Radiation-induced meningiomas are known to occur after high- and low-dose cranial radiation therapy. The goal of this study was to discern the distinguishing findings and characteristics of radiation-induced meningiomas.

Methods. The records of 16 patients (seven men and nine women) who fulfilled the criteria for radiation-induced meningiomas were retrospectively reviewed. Clinical, histopathological, cytokinetic, and cytogenetic findings as well as the patients' outcome were analyzed.

The mean age of the patients was 38.8 years and the mean tumor latency was 26.5 years. Five patients had multiple meningiomas in the irradiated field. The recurrence rate was 100% after the initial resection; 62% of patients had a second recurrence and 17% had a third recurrence. Thirty-eight percent of patients had atypical or malignant histopathological findings. The presence of progesterone receptors and low proliferation indices in these patients did not correlate with benign tumor behavior. Cytogenetic analysis showed multiple clonal aberrations in all tumors studied. The most frequent aberrations were found on chromosomes 1p, 6q, and 22. Derivative, lost, or additional chromosome 1p was found in 89% of cases and loss or deletion on chromosome 6 was found in 67%.

Conclusions. The age of patients at presentation with meningioma and the latency period of radiation-induced meningiomas are dose related. These tumors are more aggressive and are certain to recur, have a higher histopathological grade, and are associated with complex cytogenetic aberrations particularly involving 1p and 6q.

Association of loss of 1p and alterations of chromosome 14 in meningioma progression

Meningiomas are usually benign tumors; however, they can recur after surgical resection and occasionally show histologic progression to a higher grade II and III malignancy. The second most frequently reported genetic abnormality after 22q loss is deletion of 1p, although alterations in 9q, 10q, and 14q are also implicated in meningioma progression. Fourteen tumors comprising six benign, four atypical, and four malignant meningiomas were examined by means of cytogenetic and fluorescence in situ hybridization analysis. All tumors showed losses in different regions of 1p, with 1p11, 1p13, 1p21, 1p22, 1p32, and 1q21 breakpoints; eight tumors also presented alterations of chromosome 14. Five of the six cases with deletions on 1p and normal chromosome 14 were grade I, and two were recurrent. All but one of the eight cases with simultaneous 1p deletion and alterations of chromosome 14 were grade II (3 cases) and grade III (4 cases); all the grade III cases were recurrent. These results support the possible association between changes in 1p and chromosome 14 with the evolution of aggressive meningiomas through tumor progression.

Loss of 1p and 7p in radiation-induced meningiomas identified by comparative genomic hybridization

Cytogenetic and molecular studies of radiation-induced meningiomas (RIM) are rare and controversial. While comparative genomic hybridization (CGH) analysis identified monosomy 22 as the predominant change in RIM, occurring in frequencies comparable to those found in spontaneous meningioma (SM), molecular genetic analysis shows infrequent loss of chromosome 22 DNA markers. We have performed CGH analysis of six additional cases of RIM and detected an unbalanced genome in five of 6 cases. Loss of 1p and 7p was identified in the majority of RIM with an abnormal karyotype (4/5 cases), whereas loss of 6q occurred in three of five cases. Only one of five RIM had monosomy for chromosome 22. Loss of 7p is not frequently reported in SM and yet it was detected in four of 5 RIM with an abnormal karyotype in our study. Molecular and cytogenetic studies of chromosome 7 copy number should be attempted on a larger number of RIM to further investigate the role of 7p loss in RIM.

Gamma knife radiosurgery and its possible relationship to malignancy: a review

✓ The question has been raised recently whether gamma knife radiosurgery (GKS) can induce secondary neoplasia. Because there is little or no detailed knowledge about this potential complication, background information culled from the radiotherapy literature is reviewed as a guide to the clinical situations in which radiotherapy may induce secondary neoplastic change. Available case reports are then reviewed and discussed against the background of the current knowledge. On the basis of the review, the following suggestions are proposed on how to limiting the extent of this complication, document its frequency, and inform patients. It should be remembered that: the benefits of GKS are great; its alternatives also have risks; there often are no alternatives to GKS; follow-up documentation should be pursued more actively so that, if possible, no patient falls through the net; practitioners should be proactive in defining the problem, and genetic analysis of tumor biopsy specimens obtained in patients who will undergo or have undergone GKS should become routine; the extent of secondary neoplasia is not known; and patient information should be guided by what is known rather than by what is feared.

Radiation injury to the nervous system

This article reviews the current knowledge with regard to neurotoxicity of conventional radiation, including recent understanding of the pathophysiology, molecular biology, diagnostic evaluation and clinical presentations, as well as proposed treatment modalities and possible protective agents.