General Information About Childhood Central Nervous System (CNS) Atypical Teratoid/Rhabdoid Tumor
Dramatic improvements in survival have been achieved for children and adolescents with cancer. Between 1975 and 2010, childhood cancer mortality decreased by more than 50%. Childhood and adolescent cancer survivors require close follow-up because cancer therapy side effects may persist or develop months or years after treatment. (Refer to the PDQ summary on Late Effects of Treatment for Childhood Cancer for specific information about the incidence, type, and monitoring of late effects in childhood and adolescent cancer survivors.)
Primary brain tumors are a diverse group of diseases that together constitute the most common solid tumor of childhood. The PDQ childhood brain tumor treatment summaries are primarily organized according to the World Health Organization classification of nervous system tumors.[2,3] Brain tumors are classified according to histology, but immunohistochemical analysis, cytogenetic and molecular genetic findings, and measures of mitotic activity are increasingly used in tumor diagnosis and classification. Tumor location and extent of spread are important factors that affect treatment and prognosis. For a full description of the classification of nervous system tumors and a link to the corresponding treatment summary for each type of brain tumor, refer to the PDQ summary on Childhood Brain and Spinal Cord Tumors Treatment Overview.
Central nervous system (CNS) atypical teratoid/rhabdoid tumor (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. About one-half of AT/RTs arise in the posterior fossa. The diagnostic evaluation includes magnetic resonance imaging (MRI) of the neuraxis and lumbar cerebrospinal fluid examination. AT/RT has been linked to somatic and germline mutations of SMARCB1, a tumor suppressor gene. There is no current standard treatment for children with AT/RT. Multimodal treatment consisting of surgery, chemotherapy, and radiation therapy is under evaluation.
Based on present biologic 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 is referring to CNS AT/RT.Incidence
The exact incidence of childhood CNS AT/RT is difficult to determine because the tumor has been widely recognized for only the last decade.
- In two North American prospective studies performed by the Children’s Cancer Group and the Pediatric Oncology Group for children aged 3 years or younger at diagnosis, retrospective review disclosed that approximately 10% of children with brain tumors had AT/RTs.
- A Taiwanese study found that AT/RTs account for 26% of primitive or embryonal tumors in children younger than 3 years.
- The Austrian Brain Tumor Registry, conducted between 1996 and 2006, confirmed that AT/RTs represent the sixth most common malignant brain tumor among 311 newly diagnosed children (6.1%), with a peak incidence during the first 2 years of life.
The incidence in older patients is unknown. However, in the Central Nervous System Atypical Teratoid/Rhabdoid Tumor Registry (AT/RT Registry), 12 (29%) of the 42 patients were older than 36 months at the time of diagnosis.Anatomy
In about one-half of patients, the tumor is located in the posterior fossa, although it can occur anywhere in the CNS. Tumors of the posterior fossa may occur in the cerebellopontine angle or more midline. Involvement of individual cranial nerves has also been noted.
Because AT/RT grows rapidly, patients typically have a fairly short history of progressive symptoms, measured in days to weeks. Signs and symptoms are dependent on tumor location. Young patients with posterior fossa tumors usually present with symptoms related to hydrocephalus, including the following:
- Early morning headaches.
They may also develop ataxia or regression of motor skills.
Data from the AT/RT Registry suggest that approximately 20% of patients present with disseminated disease. Dissemination is typically through leptomeningeal pathways seeding the spine and other areas of the brain. There are also reports of rare patients with synchronous renal rhabdoid tumor and CNS AT/RT.Diagnostic Evaluation
All patients with suspected childhood AT/RT should have MRI of the brain and spine. Unless medically contraindicated, patients should also have lumbar cerebrospinal fluid inspected for evidence of tumorPatients may also undergo renal ultrasound to detect synchronous tumors.
AT/RT cannot be reliably distinguished from other malignant brain tumors based on clinical history or radiographic evaluation. Surgery is necessary to obtain tissue and confirm the diagnosis of AT/RT. Immunostaining for loss of SMARCB1 (INI1, hSNF5) protein expression is used to confirm the diagnosis, especially in children younger than 3 years.Prognosis
Prognostic factors that affect survival for AT/RTs are not fully delineated.
Known factors associated with a poor outcome include the following:
- Germline mutation.
- Age younger than 2 years.
- Metastases at diagnosis.
- Subtotal resection.
Most published information on outcomes for patients with AT/RT is based on small series and is retrospective in nature. Initial retrospective studies reported an average survival from diagnosis of only about 12 months.[4,8,14-16] In a retrospective report, 2-year overall survival was better for patients who underwent a gross-total resection than for those who had a subtotal resection. However, in this study the effect of radiation therapy on survival was less clear.
There are reports of long-term survivors. Notably, improved survival has been reported for those receiving intensive multimodal therapy.
- Children aged 3 years and older who received postoperative craniospinal irradiation and high-dose, alkylator-based chemotherapy had improved survival compared with those younger than 3 years with AT/RT. In this report, the incidence of leptomeningeal metastases was also higher in the infant group of patients.
- In one prospective study of 25 children with AT/RT receiving intensive multimodal therapy, including radiation and intrathecal chemotherapy, the reported 2-year progression-free survival rate was 53%, and the overall survival rate was 70%.
- Smith MA, Altekruse SF, Adamson PC, et al.: Declining childhood and adolescent cancer mortality. Cancer 120 (16): 2497-506, 2014. [PUBMED Abstract]
- Louis DN, Ohgaki H, Wiestler OD, et al., eds.: WHO Classification of Tumours of the Central Nervous System. 4th ed. Lyon, France: IARC Press, 2007.
- Louis DN, Ohgaki H, Wiestler OD, et al.: The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 114 (2): 97-109, 2007. [PUBMED Abstract]
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- Biegel JA, Fogelgren B, Wainwright LM, et al.: Germline INI1 mutation in a patient with a central nervous system atypical teratoid tumor and renal rhabdoid tumor. Genes Chromosomes Cancer 28 (1): 31-7, 2000. [PUBMED Abstract]
- Bruggers CS, Bleyl SB, Pysher T, et al.: Clinicopathologic comparison of familial versus sporadic atypical teratoid/rhabdoid tumors (AT/RT) of the central nervous system. Pediatr Blood Cancer 56 (7): 1026-31, 2011. [PUBMED Abstract]
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- Chi SN, Zimmerman MA, Yao X, et al.: Intensive multimodality treatment for children with newly diagnosed CNS atypical teratoid rhabdoid tumor. J Clin Oncol 27 (3): 385-9, 2009. [PUBMED Abstract]