A diffuse intrinsic pontine glioma (DIPG) is an aggressive type of childhood cancerous tumor that forms in the brain stem. That’s the area at the base of your brain that connects the brain to the spine. The brain stem controls most of your basic functions: vision, hearing, talking, walking, eating, breathing, heart rate, and more.
Gliomas are tumors that grow from glial cells, which are found throughout the nervous system. They surround and support nerve cells, called neurons.
DIPG is difficult to treat, and it most often develops in children between the ages of 5 and 9. However, DIPG can affect anyone at any age. The condition is rare. About 300 children a year are diagnosed with DIPG in the United States.
Like other cancers, DIPG is graded based on the nature of the tumors. Low-grade tumor cells (grade I or grade II) are the closest to normal cells. A grade I tumor is considered pilocytic, while a grade II tumor is called fibrillary. These are the least-aggressive stages of the tumors.
High-grade tumors (grade III or grade IV) are the most aggressive tumors. A grade III tumor is anaplastic, and a grade IV glioma is also known as a glioblastoma multiforme. DIPG tumors grow by invading healthy brain tissue.
Because DIPG tumors are located in such a sensitive area, it’s often not safe to take a small tissue sample for study — a procedure known as a biopsy. When they’ve grown larger and are easier to biopsy, they’re usually grade III or grade IV.
Because the tumor affects the cranial nerves, some of the earliest signs of DIPG can be seen in the face. There are 12 cranial nerves that control facial expressions, sight, smell, taste, tears, and many other functions related to the facial muscles and senses.
Initial symptoms of DIPG include changes in your child’s facial muscles, typically involving the eyes and eyelids. Your child may have trouble looking to one side. The eyelids may droop and your child may not be able to close both eyelids completely. Double vision can also be a problem. Typically, symptoms affect both eyes, not just one.
DIPG tumors can grow quickly, meaning new symptoms may appear without warning. One side of the face may droop. Your child may suddenly develop problems hearing, chewing, and swallowing. Symptoms can extend to the limbs, causing weakness in the arms and legs and making standing and walking more difficult.
If the tumor causes a disruption in the flow of spinal fluid around the brain, which then increases pressure inside the skull (hydrocephalus), symptoms can include a painful headache, as well as nausea and vomiting.
Researchers are still learning about the causes and risk factors for DIPG. They have identified a couple of genetic mutations that are associated with DIPG, but more research is needed to better understand the origins of this condition.
In addition to a physical examination, your doctor will likely run several tests to help confirm a diagnosis. Two imaging tests can identify tumors growing in the brain. One is a computerized tomography (CT) scan and the other is a magnetic resonance imaging (MRI) scan.
A CT scan uses a special kind of X-ray technology and computers to create cross-sectional images (also known as slices) of a particular body part. A CT scan is usually more detailed than an X-ray.
An MRI uses radio waves and a large magnetic field to create images of inside the body. An MRI is helpful in distinguishing between a tumor and normal tissue and swelling that might be related to the tumor.
A biopsy can also help determine if the tumor is cancerous, but surgeons can’t safely perform this procedure on many DIPG tumors.
Radiation therapy is the main therapy for children newly diagnosed with DIPG cancer. It’s usually reserved for children over the age of 3. The treatment involves high-energy X-rays that kill cancer cells and shrink tumors. Radiation is still just a temporary treatment and is not viewed as a cure for DIPG.
Chemotherapy, which uses powerful chemicals to destroy cancer cells, is sometimes used along with radiation therapy. But this combination treatment is also not a permanent cure.
Surgery is rarely used, because of the great risk of operating on tumors so close to the brain stem in a young child. In some cases, as much of the tumor as possible is surgically removed. But for many children, surgery is simply not a treatment option.
Two studies have shown some encouraging results in identifying a genetic mutation that could be treated with medications. Researchers with the St. Jude-Washington University Pediatric Cancer Genome Project have found that almost 80 percent of DIPG tumors contain a specific mutation in the gene for the protein histone H3. In animal experiments, drugs known as PRC2 and BET inhibitors helped block the activity of histone H3, preventing the growth of tumors and prolonging life.
A second study that examined the role of the enzyme PRC2 found that a drug called tazemetostat (a PRC2 inhibitor) reduced DIPG cell growth. More research is needed on these treatments, but scientists are enthusiastic about the potential for targeting histone H3 or PRC2 and prolonging the lives and improving the quality of life for young cancer patients.
To support promising research, the Michael Mosier Defeat DIPG Foundation and the ChadTough Foundation awarded research grants and fellowships worth more than $1 million in December 2017. Parents of children with this condition have reason to be hopeful.
A diagnosis of DIPG can be life-altering news. The condition is currently considered fatal. But searching for a cure is an active area of research around the world, and there are also clinical trials currently underway. To learn more about ongoing or upcoming clinic trials, visit https://clinicaltrials.gov/ct2/show/NCT03101813.
Researchers are trying to learn as much as they can about this disease in hopes of unlocking a lasting treatment or finding ways to prevent DIPG from developing in children who have the genetic mutations associated with it.