Atypical teratoid rhabdoid tumor (ATRT)

Overview

Atypical teratoid rhabdoid tumor (ATRT) is a very rare, fast growing cancer that starts in the brain or spinal cord. It's a cancerous type of brain tumor. Cancerous tumors also are called malignant tumors.

The World Health Organization (WHO) classifies ATRT as a grade 4 tumor, which means it's aggressive and tends to grow and spread quickly. ATRT is grouped into three molecular types: ATRT-TYR, ATRT-SHH and ATRT-MYC.

ATRT happens mainly in very young children, usually under age 3. But it also can occur in older kids, teenagers and, very rarely, adults.

ATRT can form in different parts of the central nervous system. Common areas include the cerebellum and the brain stem. The cerebellum helps with balance. The brain stem controls breathing and heart rate. ATRT also can occur in the spinal cord.

Treatment usually includes surgery to take out as much of the tumor as is safely possible. Then medicine called chemotherapy is used. Depending on age and whether the tumor has spread, radiation therapy may be added.

Outcomes vary by age, stage and treatment plan. Survival tends to be better for children age 3 or older when the tumor has not spread and when aggressive therapy is possible. Survival is lower for babies and when there is spread at diagnosis.

Types

Researchers have found that ATRT is not a single disease. There are three main molecular ATRT types based on gene activity: ATRT-TYR, ATRT-SHH and ATRT-MYC.

• ATRT-TYR usually affects babies younger than 1 year of age. It tends to form in the back of the brain and may spread through the spinal fluid.
• ATRT-SHH tends to occur in toddlers around 2 years old. It can occur in the upper or lower part of the brain. It shows activity in a cell signaling pathway called the sonic hedgehog (SHH) pathway. The signals in this pathway control how brain cells grow and develop.
• ATRT-MYC is more common in older preschoolers and school-age children but sometimes happens in adults. It tends to form in the upper part of the brain and may grow more quickly than the other types. Median age at diagnosis is about 27 months, with many diagnoses made at age 3 or older.

These types of ATRT help researchers study which treatments work best for each type. In the future, this information may help guide care and improve survival.

Symptoms

Symptoms of atypical teratoid rhabdoid tumor (ATRT) depend on the tumor's size and where it forms in the brain or spinal cord. Because ATRT grows quickly, symptoms often appear suddenly and worsen over days or weeks.

Common signs of ATRT include:

• Headaches that are often worse in the morning.
• Nausea or vomiting.
• Trouble with balance, walking or coordination.
• Changes in behavior or activity level.
• Unusual sleepiness or irritability.
• Seizures.
• Weakness or loss of movement in part of the body.

When ATRT affects the spinal cord, it can cause back pain, weakness in the legs, or changes in bladder or bowel function.

Symptoms in babies

In babies, symptoms can be harder to see. Parents may notice rapid head growth or a bulging soft spot on top of the head. Babies may become unusually sleepy or fussy or not have much appetite. Vomiting, poor head control, or sudden eye or limb movements also can occur.

Because babies cannot describe pain or headaches, physical signs such as increased head size, slowed development or changes in alertness are important clues.

Symptoms in children

In older infants and young children, ATRT often causes changes in mood or coordination. A child may become clumsier, lose balance, or have new trouble walking or using one side of the body. Headaches, nausea and vomiting also are common.

Some children have vision changes, facial weakness or crossed eyes if the tumor presses on the nerves that control eye or face muscles. Others may develop seizures or loss of appetite.

Can ATRT be detected early?

ATRT is difficult to detect early because it grows fast and symptoms often resemble common childhood illnesses. There is no routine screening test for ATRT. Most tumors are found after children show signs of the condition and have imaging such as MRI.

Families with a known SMARCB1 or SMARCA4 gene change may have regular checkups or imaging as part of genetic counseling or surveillance plans.

When to seek care

Because ATRT grows quickly, contact your child's care team as soon as symptoms appear or change. Seek medical attention right away if a child has symptoms such as persistent headaches, vomiting, or trouble with balance, walking or coordination.

Reach out if a baby's head size increases faster than expected or the soft spot bulges. Other warning signs include new seizures, sleepiness that is not typical and weakness on one side of the body.

These symptoms can have many causes, but sudden or worsening changes need prompt exam. If ATRT or another serious condition is suspected, imaging such as an MRI can help find the cause and guide next steps.

Causes

ATRT is one of many types of pediatric brain tumors. It develops when certain genes that control how cells grow and divide stop working. When these control signals break down, cells in the brain or spinal cord can grow out of control and form a tumor.

The genes most often affected are SMARCB1 and SMARCA4. They help cells make a protein that keeps growth in check. When one of these genes is missing or damaged, the protein is not made correctly. Then cells divide too fast and become cancerous.

Most ATRTs are linked to changes in genes that control how cells grow. In most tumors, the SMARCB1 gene, also called INI1, stops working. A smaller number affect the SMARCA4 gene. Some people are born with a change in one of these genes in all their cells. This raises the chance of rhabdoid tumors and is called rhabdoid tumor predisposition syndrome.

Most of these gene changes happen by chance after birth and are not passed down from parents. But in some people, the change is inherited and present in every cell of the body. That inherited form increases the risk of ATRT and other rhabdoid tumors.

Experts do not know why these gene changes occur in most people with ATRT. The tumors are not caused by injury, diet or environmental factors. Nothing a parent did or did not do causes the tumor to form.

Risk factors

ATRT can affect anyone, but it happens most often in very young children. Most tumors occur before age 3. ATRT is rare in older children and extremely rare in adults.

The condition affects all genders in similar numbers. There is no known link to lifestyle, environment or family habits.

Some people are born with a change in one of two genes called SMARCB1 and SMARCA4. The change can increase the risk of developing ATRT or a related tumor. This increased risk is called rhabdoid tumor predisposition syndrome.

ATRT in adults

Adult cases are extremely rare and make up only a small fraction of all ATRT diagnoses. When ATRT appears in adults, it often develops in the upper part of the brain and causes headache, seizures or weakness. Treatment follows the same general approach as in children, with surgery, chemotherapy and radiation.

Complications

ATRT can cause serious complications because it grows quickly and can spread through the fluid that surrounds the brain and spinal cord. This spread, called metastasis, makes treatment more complex and can lower survival rates.

The tumor itself can increase pressure inside the skull, leading to headaches, vomiting or changes in alertness. If it blocks the typical flow of cerebrospinal fluid, hydrocephalus can occur and may require surgery to relieve pressure. Hydrocephalus is a buildup of fluid in the brain.

Treatment for ATRT also can lead to complications. Surgery, chemotherapy and radiation can affect thinking, growth or hormone function, especially in very young children. These side effects may appear months or years after treatment ends.

Even after successful treatment, ATRT can come back. This is called recurrence. It often happens within the first few years after diagnosis, so regular follow-up imaging is important.

Because the brains and bodies of very young children are still developing, treatment-related late effects, such as changes in learning, growth or hormone levels, may appear years later.

Prevention

There is no known way to prevent ATRT. Most tumors happen without any warning or family history.

Because ATRT is linked to changes in the SMARCB1 or SMARCA4 genes, some families may choose genetic counseling. This can help identify whether a child or relative carries a gene change that increases the chance of developing a rhabdoid tumor.

If a gene change is found, regular checkups and imaging may help detect any tumors early. These steps cannot prevent ATRT but can allow care teams to start treatment sooner.

ATRT is not caused by injury, diet or environmental exposures. Nothing a parent did or did not do causes this tumor to form.

Researchers continue to study the genetic and molecular causes of ATRT to better understand how to prevent it in the future.