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Atypical Teratoid / Rhabdoid Tumor (AT/RT)

What is AT/RT?

Atypical teratoid/rhabdoid tumor (AT/RT) is a fast-growing embryonal tumor of the brain and spinal cord. AT/RT is very rare, accounting for about 1-2% of central nervous system (CNS) tumors in children. AT/RT most often occurs in young children under 3 years of age. Approximately 50% of embryonal tumors in infants under 1 year of age are AT/RTs. There are about 75 new cases of AT/RT each year in the United States.

The most common places for AT/RT to develop are the cerebellum and brain stem. AT/RT is an aggressive and fast-growing cancer. Treatment usually involves a combination of therapies which may include surgery, chemotherapy, and radiation therapy. Even with current treatments, this is a very difficult cancer to cure.

Atypical Teratoid/Rhabdoid Tumor (AT/RT) is an aggressive and fast-growing tumor. Using magnetic resonance imaging (MRI), doctors can see the size and location of the tumor.

Atypical Teratoid/Rhabdoid Tumor (AT/RT) is an aggressive and fast-growing tumor. Using magnetic resonance imaging (MRI), doctors can see the size and location of the tumor.

Risk Factors and Causes of AT/RT

Most AT/RTs occur in children ages 3 and younger. But these tumors may also occur in older children and adults. Malignant rhabdoid tumors are closely related to tumors that occur in other locations in the body such as the kidney (rhabdoid tumor of the kidney).

About 95% of AT/RT cases are related to a gene that does not function properly. This gene, called SMARCB1, is a tumor suppressor gene. In less than 5% of cases, AT/RTs are due to a defect in another tumor suppressor gene called SMARCA4. These tumor suppressor genes normally make a protein to stop tumor growth. When the gene does not work, the protein is not made, and tumor growth is not controlled. This gene change may be inherited (germline mutation), or it may only occur in the cells of the tumor. Most of the time, the gene mutation is only in the cells of the tumor. However, all patients with rhabdoid tumors should have testing for gene mutations and receive genetic counseling.

Malignant rhabdoid tumors have a common abnormal gene: a change in the SMARCB1 gene (also known as INI1, SNF5, and BAF47 gene). Sometimes, malignant rhabdoid tumor is caused by a mutation in the SMARCA4 gene. 15-30% of children have this mutation in every cell in their body (germline mutation). In most cases, the gene mutation occurs only in the tumor. Genetic testing and counseling is important for families of patients with rhabdoid tumor. Children with the germline mutation have a higher risk of developing second tumors.

Signs and Symptoms of AT/RT

Symptoms of AT/RT vary widely based on the child’s age and tumor location. These tumors grow quickly, and symptoms may worsen in a very short period of time. AT/RT symptoms may include:

  • Headache, often worse in the morning and/or improves after vomiting
  • Nausea and vomiting
  • Changes in activity levels, lethargy
  • Fatigue or sleepiness
  • Loss of balance, coordination or problems walking
  • Asymmetric eye or face movements 
  • Change in behavior, irritability
  • Increased head size in infants
  • Increased fullness of the fontanel ("soft spot" at the top of the skull)

Diagnosis of AT/RT

Doctors test for AT/RT in several ways. 

  • A health history and physical exam helps doctors learn about symptoms, general health, past illness, and risk factors.
  • Genetic testing and counseling is also recommend for patients with AT/RT. Patients are tested for the SMARCB1 and SMARCA4 genes.
  • A neurological exam examines the function of the brain, spinal cord, and nerves. These tests measure different aspects of functioning including memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
  • Imaging tests such as magnetic resonance imaging (MRI) create detailed pictures of the brain and spinal cord. Doctors can see the size and location of the tumor and better understand what areas of the brain might be affected. AT/RTs can look similar to other tumors on imaging, so further testing is needed for a diagnosis. An ultrasound of the kidney may be performed to check for rhabdoid tumor of the kidney.
  • A lumbar puncture may be performed to look for cancer cells in the cerebrospinal fluid.
  • A biopsy is performed to diagnose AT/RT. In a biopsy, a small sample of the tumor is removed during surgery using a needle. A pathologist looks at the tissue sample under a microscope to identify the specific type of tumor. The cells of AT/RT look different from healthy cells. Cellular markers in the tissue are used to examine specific proteins in the cells. A specific antibody stain is used to check for the SMARCB1 or SMARCA4 protein in the cancer cells. AT/RT cells lack this protein, which confirms the diagnosis of the tumor.
An ultrasound may be performed to check for rhabdoid tumor of the kidney.

An ultrasound may be performed to check for rhabdoid tumor of the kidney.

Staging of AT/RT

There is no standard staging system for AT/RT. Tumors are classified as newly diagnosed or recurrent. AT/RT is an aggressive cancer. Approximately 15-30% of patients have spread of disease to the meninges or cerebrospinal fluid (CSF) at diagnosis. This spread of disease to the meninges is called leptomeningeal metastases.

Prognosis for Children with AT/RT

AT/RTs are fast-growing and difficult to treat. Prognosis is usually poor, but advances in therapy have helped some children.

Factors that influence prognosis include:

  • Age of the child. Children under 3 years old have a poorer prognosis.
  • Whether the cancer has spread to other areas of the brain and spinal cord or to the kidney at the time of diagnosis.
  • How much of the tumor remains after surgery. Complete resection of the tumor improves chance of survival.

The 5-year survival rate for children with AT/RT is approximately 50%. However, this varies widely depending upon the age at diagnosis and the presence of metastases. Children less than 3-years of age with metastatic disease have the worst prognosis with less than 10% chance of long term cure.

Treatment of AT/RT

Treatment depends on several factors including the size and location of the tumor and the child’s age. AT/RT is a very aggressive cancer, and most patients will receive multiple types of treatments. AT/RT treatment may include surgery, chemotherapy, and radiation. Treatment for this disease is often through a clinical trial.

  1. Surgery is used to both diagnose and treat AT/RT. If AT/RT is confirmed with a biopsy, the surgeon will remove as much of the tumor as possible. These tumors are often difficult to remove completely because of their location in the brain and how quickly they spread.

  2. Chemotherapy is often used along with surgery and/or radiation to treat AT/RT. Chemotherapy may systemic, regional or intrathecal. High dose chemotherapy is also used to treat this cancer.

  3. Radiation therapy is sometimes used in addition to other treatments. The type of radiation therapy used depends on the location of the tumor and if it has spread.

    Radiation therapy uses beams of radiation, X-rays or protons, to shrink tumors and kill cancer cells. Radiation works by damaging the DNA inside cancer cells.

    Radiation therapy uses beams of radiation, X-rays or protons, to shrink tumors and kill cancer cells. Radiation works by damaging the DNA inside cancer cells.

  4. Children with AT/RT are eligible for ongoing clinical trials using targeted therapy. These therapies are used at the time of diagnosis or at recurrence. Targeted therapies include the aurora kinase A inhibitor, alisertib, and the EZH2 inhibitor, tazemetostat. Immunotherapy is also being studied in the treatment of AT/RT.

  5. Supportive care for ATRT patients includes appropriate rehabilitation and neurological consultation. Steroid and anti-seizure medications may be needed. Additional support may be needed to address issues in learning, developmental milestones, and coping with cancer.

Life after AT/RT 

Children with AT/RT and germline SMARCB1 or SMARCA4 alterations have rhabdoid tumor predisposition syndrome. They and other family members should receive genetic testing and counseling since they are at an increased risk of developing other tumors. These children need additional monitoring including periodic ultrasound exams of the kidney to monitor for the development of kidney tumors.

Children treated for AT/RT should be monitored for adverse effects of treatment. Late effects may include neurocognitive and endocrine problems due to radiation. Chemotherapy and radiation therapy also increase risk for second cancers. Families should talk to their doctors about risks related to the specific treatments children received.

Supportive Care for Children with AT/RT 

Especially for younger children, the prognosis for AT/RT is poor. Balancing quality of life with cancer-directed therapy is important. Families should talk to their care team about what problems to expect and ways to help manage them. Including palliative care or quality of life services can help families manage symptoms, navigate difficult conversations, and make decisions that align family wishes with goals of care.

More: Life After Brain Tumors

Reviewed: June 2018