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Primary brain tumors, including atypical teratoid/rhabdoid tumors (AT/RTs), are a diverse group of diseases that together constitute the most common solid tumors of childhood. The PDQ childhood brain tumor treatment summaries are primarily organized according to the World Health Organization classification of nervous system tumors.[
CNS AT/RT is a rare, clinically aggressive tumor that most often affects children aged 3 years and younger but can occur in older children and adults. Approximately one-half of AT/RTs arise in the posterior fossa.[
Based on current biological understanding, AT/RT is part of a larger family of rhabdoid tumors. In this summary, the term AT/RT refers to CNS tumors only, and the term rhabdoid tumor reflects the possibility of both CNS and non-CNS tumors. Unless specifically noted in the text, this summary refers to CNS AT/RT.
Childhood and adolescent cancer survivors require close monitoring because side effects of cancer therapy may persist or develop months or years after treatment. For specific information about the incidence, type, and monitoring of late effects in childhood and adolescent cancer survivors, see Late Effects of Treatment for Childhood Cancer.
Incidence
The exact incidence of childhood CNS AT/RT is difficult to determine because the tumor is rare and has only been recognized since 1996.[
The incidence in older patients is unknown. However, in the Central Nervous System Atypical Teratoid/Rhabdoid Tumor Registry (AT/RT Registry), 12 of the 42 patients (29%) were older than 36 months at the time of diagnosis.[
Anatomy
Anatomy of the inside of the brain, showing the pineal and pituitary glands, optic nerve, ventricles (with cerebrospinal fluid shown in blue), and other parts of the brain. The tentorium separates the cerebrum from the cerebellum. The infratentorium (posterior fossa) is the region below the tentorium that contains the brain stem, cerebellum, and fourth ventricle. The supratentorium is the region above the tentorium and denotes the region that contains the cerebrum.
Clinical Presentation
Childhood AT/RT is a clinically aggressive tumor that primarily occurs in children younger than 3 years, but it also can occur in older children and adults.[
Approximately one-half of all AT/RTs arise in the posterior fossa, although they can occur anywhere in the CNS.[
Because AT/RTs grow rapidly, patients often have a fairly short history of progressive symptoms, measured in days to weeks. Signs and symptoms depend on tumor location. Young patients with posterior fossa tumors usually present with symptoms related to hydrocephalus, which include the following:
They may also develop ataxia, regression of motor skills, or localizing symptoms related to cranial nerve dysfunction.
Registry data suggest that 25% to 30% of patients present with disseminated disease.[
Diagnostic Evaluation
All patients with suspected AT/RT should undergo MRI of the brain and spine. Unless medically contraindicated, the lumbar cerebrospinal fluid should be inspected for evidence of tumor. Patients may also undergo renal ultrasonography to detect synchronous tumors. Germline testing is also indicated.
AT/RTs cannot be reliably distinguished from other malignant brain tumors on the basis of clinical history or radiographic evaluation alone. Surgery is necessary to obtain tissue and confirm the diagnosis. Immunohistochemical staining for loss of SMARCB1 protein expression is also used to confirm the diagnosis.[
Prognosis
Prognostic factors that affect survival for patients with AT/RTs are not fully delineated.
Known factors associated with a poor outcome include the following:
Most published data on outcomes of patients with AT/RT are from small series and are retrospective in nature. Initial retrospective studies reported an average survival from diagnosis of only about 12 months.[
There are reports of long-term survivors.[
References:
Childhood central nervous system (CNS) atypical teratoid/rhabdoid tumor (AT/RT) was first described as a discrete clinical entity in 1987 [
Histologically, AT/RT is morphologically heterogeneous, typically containing sheets of large epithelioid cells with abundant eosinophilic cytoplasm and scattered rhabdoid cells, most often with accompanying components of primitive neuroectodermal cells (small round blue cells), mesenchymal cells, and/or glial cells.[
Immunohistochemical staining for epithelial markers (cytokeratin or epithelial membrane antigen), glial fibrillary acidic protein, synaptophysin (or neurofilament), and smooth muscle (desmin) may help to identify the heterogeneity of differentiation, but will vary depending on the cellular composition.[
Immunohistochemical staining for the SMARCB1 protein is useful in establishing the diagnosis of AT/RT. A loss of SMARCB1 staining is noted in neoplastic cells, but staining is retained in non-neoplastic cells (e.g., vascular endothelial cells).[
AT/RT is a rapidly growing tumor that can have an MIB-1 labeling index of 50% to 100%.[
Genomics of CNS Atypical Teratoid/Rhabdoid Tumor (AT/RT)
SMARCB1andSMARCA4genes
AT/RT was the first primary pediatric brain tumor in which a candidate tumor suppressor gene, SMARCB1, was identified.[
Rare cases of rhabdoid tumors expressing SMARCB1 and lacking SMARCB1 variants have also been associated with somatic or germline variants of SMARCA4, another member of the SWI/SNF chromatin-remodeling complex.[
Less commonly, SMARCA4-negative (with retained SMARCB1) tumors have been described.[
The 2021 WHO classification defines AT/RT by the presence of either SMARCB1 or SMARCA4 alterations. Tumors with histological features of AT/RT that lack these genomic alterations are termed CNS embryonal tumors with rhabdoid features.[
Despite the absence of recurring genomic alterations beyond SMARCB1 and SMARCA4,[
In a subsequent study, the AT/RT SHH subgroup was further divided into three subtypes: SHH-1A, SHH-1B, and SHH-2.[
Loss of SMARCB1 or SMARCA4 protein expression has therapeutic significance, because this loss creates a dependence of the cancer cells on EZH2 activity.[
Cribriform Neuroepithelial Tumor
Cribriform neuroepithelial tumor has genomic and epigenomic characteristics that are very similar to those of AT/RT TYR.[
Rhabdoid Tumor Predisposition Syndrome (RTPS)
RTPS, which is primarily related to germline SMARCB1 alterations (and less commonly to germline SMARCA4 alterations), has been clearly defined.[
This syndrome is manifested by a marked predisposition to the development of malignant rhabdoid tumors in infancy and early childhood. Up to one-third of AT/RTs are thought to arise in the setting of RTPS, and most of these occur within the first year of life. The most common non-CNS malignancy of RTPS is malignant rhabdoid tumor of the kidney, which is also noted in infancy.[
A study of 65 children with rhabdoid tumors found that 23 (35%) had germline variants and/or deletions of SMARCB1.[
Gonadal mosaicism has also been observed, as evidenced by families in which multiple siblings are affected by AT/RT and have identical SMARCB1 alterations, but both parents lack a SMARCB1 variant/deletion.[
For more information about RTPS1 and SMARCB1, see Rhabdoid Tumor Predisposition Syndrome Type 1.
References:
There is no evidence-based staging system for childhood central nervous system atypical teratoid/rhabdoid tumor. For treatment purposes, patients are classified as having newly diagnosed or recurrent disease, with or without neuraxis dissemination.
An evidence-based standard treatment for children with newly diagnosed central nervous system (CNS) atypical teratoid/rhabdoid tumor (AT/RT) has not yet been defined. Given the highly aggressive nature of the tumor, most patients have been treated with intensive multimodality therapy. However, the extent of treatment, particularly for radiation therapy, is limited because of the young age of most patients.
Treatment options for newly diagnosed CNS AT/RT include the following:
Surgery, Chemotherapy, and Radiation Therapy (Multimodality Therapy)
The extent of surgical resection may affect survival. Data from the Central Nervous System Atypical Teratoid/Rhabdoid Tumor Registry (AT/RT Registry) suggest that patients who have had a complete resection may have a longer median survival. However, complete surgical resection is often difficult because of the invasive nature of the tumor.[
Chemotherapy has been the main adjuvant therapy for very young children with AT/RT. Cooperative group studies that included children younger than 36 months demonstrated poor survival with standard chemotherapeutic regimens alone.[
Intensive regimens that use varying combinations of high-dose chemotherapy,[
Only two prospective trials for children with CNS AT/RT have been completed. In an institutional prospective trial, children were treated with a modified Intergroup Rhabdomyosarcoma Study-III (IRS-III) protocol, using intrathecal chemotherapy and radiation therapy. Of the subset of 20 children who completed therapy, the 2-year progression-free survival (PFS) rate was 53%, and the overall survival (OS) rate was 70%. Survival was better for patients who had a complete resection.[
Thirteen patients in the AT/RT Registry were treated with high-dose chemotherapy with hematopoietic stem cell rescue as part of initial therapy.[
Radiation therapy appears to have a positive impact on survival for patients with AT/RT.[
Evidence (radiation therapy):
Evidence (multimodality therapy):
On the basis of the two prospective studies summarized above, multimodality therapy with surgery, radiation therapy, and chemotherapy seems to be the best treatment to optimize the survival of children with AT/RT. However, toxicities can be significant, and the most effective regimen and the optimal sequencing of therapies still need to be determined.
Treatment Options Under Clinical Evaluation
Early-phase therapeutic trials may be available for selected patients. These trials may be available via the
References:
There is no standard treatment for children with recurrent central nervous system (CNS) atypical teratoid/rhabdoid tumor (AT/RT).
Trials of molecularly targeted therapy are ongoing. In a study of the EZH2 inhibitor tazemetostat in adult patients with epithelioid sarcoma and non-CNS malignant rhabdoid tumors with SMARCB1 or SMARCA4 loss, prolonged stable disease and objective responses were observed.[
Stereotactic radiation therapy/radiosurgery or focal radiation therapy can also be considered for the treatment of children with recurrent disease.[
Patients or families who desire additional disease-directed therapy should consider entering trials of novel therapeutic approaches because no standard agents have demonstrated clinically significant activity.
Regardless of whether a decision is made to pursue disease-directed therapy at the time of progression, palliative care remains a central focus of management. This ensures that quality of life is maximized while attempting to reduce symptoms and stress related to the terminal illness.
Treatment Options Under Clinical Evaluation
Early-phase therapeutic trials may be available for selected patients. These trials may be available via the
The following is an example of a national and/or institutional clinical trial that is currently being conducted:
References:
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Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of childhood central nervous system atypical teratoid and rhabdoid tumor. It is intended as a resource to inform and assist clinicians in the care of their patients. It does not provide formal guidelines or recommendations for making health care decisions.
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Board members review recently published articles each month to determine whether an article should:
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
The lead reviewers for Childhood Central Nervous System Atypical Teratoid/Rhabdoid Tumor Treatment are:
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Levels of Evidence
Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Pediatric Treatment Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.
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PDQ® Pediatric Treatment Editorial Board. PDQ Childhood Central Nervous System Atypical Teratoid/Rhabdoid Tumor Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at:
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Last Revised: 2024-04-05
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