Low-Grade Glioma

What is low-grade glioma (LGG)?

Glioma is a type of tumor that starts in glial cells in the brain and spinal cord. Glial cells protect and support nerve cells (neurons). Gliomas can be low-grade or high-grade.

Low-grade gliomas are the most common central nervous system (CNS) tumors in children.

Low-grade glioma (LGG) tumors grow slowly. These tumors can happen anywhere in the brain or spinal cord. They are most common in the cerebellum, located at the back of the brain.

Pediatric low-grade gliomas rarely spread to other parts of the brain or spinal cord. They can often be cured if they can be removed. But the tumors may happen in areas of the brain where surgery is not recommended. In these cases, patients may be treated with chemotherapy, targeted therapy, or radiation.

The survival rate for pediatric low-grade glioma depends on its type, location, and whether it can be removed by surgery. Your child’s care team is the best source of information about your child’s case.

Symptoms of low-grade glioma

The symptoms of low-grade gliomas depend on:

• Size of the tumor
• Location of the tumor
• Child’s age
• How fast the tumor grows 

Symptoms of glioma may include:

• Headaches, especially in the early morning
• Nausea and vomiting
• Vision, hearing, or speech problems
• Loss of balance or problems walking
• Handwriting problems
• Speech that is slow
• Weakness, tingling, or changes in the way the body feels on 1 side
• Unusual sleepiness
• Changes in energy level
• Changes in mood, personality, behavior, memory, or thinking
• Seizures
• Weight gain or loss for unknown reason
• Increased head size (in infants)

Risk factors for low-grade glioma

Inherited conditions

In some cases, low-grade gliomas are linked with certain inherited conditions. These disorders include:

• Neurofibromatosis type 1 (NF1) is a genetic condition that can cause skin changes, tumors on nerves, and other health problems, but its effects can be different for each person. 
• Tuberous sclerosis is a genetic condition that can cause growths in the brain, skin, and other parts of the body. It may lead to seizures, developmental delays, and other health issues.

Past radiation therapy to the brain also increases risk.

Diagnosis of low-grade glioma

Tests to diagnose low-grade glioma include:

• A physical exam and health history to learn about symptoms, general health, past illness, and risk factors.
• A complete neurological exam. This includes memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
• An eye exam to look at eye health and vision.
• Imaging tests to help identify the tumor, its size, and location. Magnetic resonance imaging (MRI) is the main imaging test. An MRI is also done after surgery to see if any tumor remains.
• A biopsy, in which surgeons remove a small tumor sample. A pathologist looks at the sample under a microscope to identify the tumor type.
• Other genetic testing of the tumor to show possible targets for targeted therapy.

Types of low-grade gliomas

Types of low-grade gliomas include:

• Pilocytic astrocytoma (the most common type of glioma)
• Subependymal giant cell astrocytoma
• Diffuse astrocytoma
• Pleomorphic xanthoastrocytoma
• Oligodendroglioma
• Ganglioglioma
• Diffuse leptomeningeal glioneuronal tumor
• Desmoplastic infantile astrocytoma and ganglioglioma
• Dysembryoplastic neuroepithelial tumor
• Papillary glioneuronal tumor
• Rosette-forming glioneuronal tumor
• Angiocentric glioma
• Chordoid glioma of third ventricle
• Polymorphous low-grade neuroepithelial tumor of the young
• Multinodular and vacuolating neuronal tumor

Recurrent/progressive glioma

Recurrent/progressive low-grade glioma happens when a glioma returns after treatment. It can grow in the same spot or in other parts of the brain or spinal cord. Sometimes, low-grade glioma can come back as a high-grade tumor. Doctors use tests to find out if the cancer has returned and where it is. Treatment for recurrent glioma depends on where the tumor has come back.

Treatment of low-grade glioma

Treatment depends on the type of tumor, its location, and whether it has spread or has come back.

Surgery for low-grade glioma

Surgery to remove as much of the tumor as possible is the main treatment for low-grade glioma. For many patients, surgery alone may be an effective treatment.

The goal is complete removal of the tumor (total gross resection). But this may not always be possible. This is due to the risk of damage to nearby brain structures.

Chemotherapy for low-grade glioma

Chemotherapy may be the main treatment if surgery is not possible. Young children may get chemotherapy to delay radiation therapy until they are older.

The chemotherapy treatment plan depends on factors such as the spread of disease and features of the tumor.

Radiation therapy for low-grade glioma

Radiation therapy is an effective treatment for low-grade glioma. But it is usually avoided until patients are at least age 10 because of the short- and long-term side effects. Proton beam radiation may be an option. 

Targeted therapy for low-grade glioma

Targeted therapies work by acting on, or targeting, certain features of tumor cells. These drugs change signals and processes that cancer cells use to grow, divide, and send messages to other cells. Stopping these activities helps kill cancer cells. 

Recently, new medicines that target certain features of tumor cells have been effective. They have fewer side effects than traditional chemotherapy or radiation therapy. Many low-grade gliomas happen because of a change in the BRAF gene. The BRAF gene helps control a protein important for cell growth and function.

Targeted therapies used or under study for low-grade gliomas include:

• MEK inhibitors such as selumetinib, trametinib, and mirdametinib can be used in the case of BRAF fusion/duplication or low-grade glioma in patients with NF1. 
• mTOR inhibitors everolimus or sirolimus can be effective in low-grade astrocytoma, especially in patients with tuberous sclerosis complex.
• BRAF inhibitors such as dabrafenib may be used for tumors with a BRAF V600 gene mutation.
• The drug tovorafenib can target cancer cells with specific BRAF fusions and other changes in the gene.

Prognosis for low-grade glioma

Low-grade gliomas do not usually spread (metastasize). In high-income countries, such as the United States, the 10-year survival rate is more than 85%. But the prognosis may vary. It depends on:

• The tumor’s specific type, location, and genetic mutations
• If the tumor was totally removed (resected)
• If the tumor is just in 1 area or if it has spread
• The child’s age
• If the tumor was newly diagnosed or has returned (recurred)
• If there are changes in specific genes such as BRAF
• If your child has NF1 or tuberous sclerosis

Support for patients with low-grade glioma

Recovery and long-term effects of low-grade glioma in children depend on the type of tumor and treatment. Rehabilitation therapy may be needed. Your child should have regular follow-up care, lab tests, and imaging tests.

Pediatric low-grade glioma as a long-term disease

Low-grade glioma is often a chronic or long-term disease. Overall survival from low-grade glioma is high. But the tumor often comes back or gets worse over time. Your child may need more treatments.

Sometimes a tumor may show growth on a scan, but the care team advises observation (watchful waiting) instead of treatment. Good communication and trust among you, your child, and the care team help with decision-making and disease management.

Regular checkups and screenings are important to watch for health problems that can develop years after therapy.

Your child will have regular MRIs after treatment has ended. MRI scans show if there is a change in your child’s condition or if the tumor has come back. 

Children who had radiation therapy for an optic pathway glioma may be at risk of vision changes. These changes are most likely to happen within 2 years after radiation therapy. The care team will closely follow the tumor growth’s effect on your child’s vision during and after treatment.

Questions to ask your care team

• What are the treatment options for my child's specific type of glioma? What are the potential risks and benefits of each treatment option?
• What follow-up care will be needed after treatment?
• What are the possible side effects of treatment, and how can we manage them?
• Are there any clinical trials or new treatments that might be suitable for my child?
• How might treatment affect my child's thinking, learning, emotional, and physical development? 
• What support services are available for my child and family?

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