Pediatric Low-Grade Gliomas: An Overview

pLGG Symptoms

Although pLGGs don't often spread, as they grow they can press on the brain and spinal cord and cause problems. Which symptoms a pLGG causes depends on how large it is and where in the brain it is growing. 

Children, teens, or young adults with pLGG can have symptoms like these:

• Double vision, blurry vision, or vision loss
• Headache, often in the morning
• Throwing up often
• Problems with balance and walking
• Seizures
• Weight gain or loss

pLGG Causes

Children are more likely to get pLGG if they have one of these genetic diseases:

Neurofibromatosis type 1. It causes noncancerous tumors to grow along nerves in the brain, skin, and other parts of a child's body.

Tuberous sclerosis complex. In this disease, tumors that look like potatoes grow in the spinal cord, eyes, lungs, kidneys, and other places. These tumors are not cancer.

Noonan syndrome. This condition affects many parts of the body. Children with Noonan syndrome may be short and have wide-set eyes, heart defects, and bleeding problems. 

Children with these conditions need regular checkups and imaging tests to look for signs of tumors.

Gene Mutations

pLGG affects a pathway in the cell called mitogen-activated protein kinase (MAPK). MAPK controls the growth of cells. Problems with this pathway can make cells divide too quickly.

A few gene changes, or mutations, affect the MAPK pathway. The most common genetic change seen in pLGG is when the genes BRAF and KIAA1549 fuse together. These are called BRAF fusions. A few other genes in the MAPK pathway can have mutations in pLGG, including:

• BRAF V600E 
• FGFR1/2
• NF1
• RAF1
• NTRK

Who Treats pLGG?

A few doctors and specialists may be involved in your child's care, including a:

• Neurologist. They diagnose and treat problems with the brain and spinal cord.
• Neuro-oncologist. They treat tumors of the brain and spinal cord.
• Neurosurgeon. This doctor performs surgery to treat brain and spinal cord tumors. Your child may also need surgery for obstructive hydrocephalus, which can happen when the tumor blocks the flow of cerebrospinal fluid (CSF) in the narrow passages that connect the brain's ventricles.

To diagnose pLGG, your child's doctor will start by asking about their symptoms and medical history. The doctor will also do a physical exam and a check of your child's nervous system. 

The doctor may order tests, including:

Imaging tests. Magnetic resonance imaging (MRI) and other imaging tests take pictures of the inside of your child's body. These tests can show where a tumor is located.

Biopsy. The doctor removes a small piece of the tumor. Then a lab tests the cells.

Lumbar puncture. The doctor places a needle into your child's spine and removes a small amount of fluid. Spinal tap is another name for this test.

Electroencephalogram (EEG). Although it isn't used to diagnose pLGG, your doctor might use it if your child is having seizures. About 13% of kids with pLGG had seizures at diagnosis. 

Treatment Types

Because pLGGs grow so slowly and your child may not have symptoms, some pLGGs may not need treatment. Instead, the doctor will check your child often with imaging scans. If the tumor does grow and have symptoms, the main treatment is surgery to safely remove as much of it as possible. The tumor must be in a part of the brain or spinal cord where a surgeon can remove it. 

Chemotherapy uses strong medicines to kill or shrink tumor cells. Chemotherapy is also an option when the tumor is in a part of the brain where it's not safe to do surgery. Combining two or more of these medicines may help them work better. The carboplatin and vincristine (CV) combination stands as a standard systemic therapy for pLGG.

Radiation is an option for older children who have no other surgical or other treatments (such as chemotherapy or targeted therapies) available.  While newer techniques like proton beam or guided intensity photon therapy are effective, they may have long-term side effects such as secondary cancers. 

Targeted therapies can be used to treat pediatric low-grade gliomas (pLGGs). These therapies may be used as single agents or in combination. Some targeted therapies for pLGGs include dabrafenib (Tafinlar), tovorafenib (Ojemda), and trametinib (Mekinist). Your health care team will work with you to help figure out the best options for your child.
 

Pediatric LGG vs. Adult LGG

In adults, gliomas are also the most common type of tumor that starts in the brain. Most adult low-grade gliomas can turn into malignant, high-grade gliomas and can spread. This rarely happens in pLGG.

Doctors treat gliomas in adults with surgery, radiation, or chemotherapy. The outlook for adults with these cancers isn't as good as the outlook for children.

Outlook With pLGG

The outlook for a child or young adult with pLGG depends on a few factors, including: 

• The type of tumor
• Where it is
• Its size
• How well it responds to treatment
• The child's age and general health

The most common type of pLGG, pilocytic astrocytoma, has a cure rate of more than 90%. Kids are at a lower risk of the tumor coming back when surgery can remove the whole tumor. But even if tumors grow, they are rarely life-threatening. Infants may have a worse outlook because their tumors are more likely to spread throughout the nervous system.

Outcomes are different for each person. The doctor can give you a better idea of your child’s possible outlook and what to expect from treatment.