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Diffuse Intrinsic Pontine Glioma (DIPG)

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive brain tumour and is difficult to treat. It occurs in an area of the brainstem (the lowest, stem-like part of the brain) called the pons, which controls many of the body's most vital functions, such as breathing, blood pressure, and heart rate. Because of its location in the brain and how rapidly it progresses, DIPG is a high grade malignant brain tumour.

DIPG is a glial tumour, which arises from the brain's glial tissue that supports and protects the brain's neurons. It makes up 10-15 per cent of all brain tumours in children.

Unfortunately, fewer than 10 per cent of children survive two years from diagnosis.

Treatment

There are limited, effective treatment options for DIPG. Surgery isn't an option because of the tumour's location in the brain stem and the nature of the diffuse and intrinsic tumour.  DIPG cells don't grow as large masses that push normal brain tissue aside. Instead, they are lumps of cells that grow into surrounding healthy tissue, mixing cancer cells with healthy cells. As a result, a surgeon can't separate normal from abnormal tissue.  

Steroids

Steroids are often used in the management of DIPGs.  At the time of diagnosis, steroids, mainly dexamethasone, are the first treatment offered to patients with DIPG. Steroid treatment aims to improve neurological symptoms, reduce the edema (swelling) surrounding the tumour that may sometimes impact the flow of the cerebrospinal fluid (CSF), and prevent or minimise the edema induced by the initiation of the radiation treatment. 

Radiation therapy

Radiation therapy uses high-energy waves from a specialised machine to damage or shrink tumours. Radiation produces responses in more than 90 per cent of children with DIPG. Unfortunately, the shrinkage is short-lived. After about six to 12 months after radiation, the DIPG tumour starts to grow again in almost all cases. Once the tumour has begun to grow again, no further treatment has been shown to improve survival. When children start to have neurologic symptoms, they are often restarted on steroids.

Experimental chemotherapy

Researchers are actively investigating chemotherapy and biologic therapy as a DIPG treatment. With a biopsy of the tumour at diagnosis, doctors may determine the selection of drugs targeted to the tumour. Multiple clinical trials have demonstrated that routine chemotherapy does not increase survival rates for this condition.

Clinical trials

Clinical trials may provide new options for children with DIPG. If you have any questions about potential clinical trials, your child's medical team is there to offer you additional eligibility information.

Risk factors

While DIPG is usually diagnosed when children are between the ages of five and nine, it can occur at any age in childhood. It occurs in boys and girls equally and only occasionally in adults.

It is unknown what causes DIPG. There are no known associations of DIPG with any environmental or infectious agents. Most researchers who study DIPG believe these brain tumours, similar to other tumours affecting children, arise when normal developmental and maturational processes go awry.

Early symptoms

The symptoms of DIPG usually develop very rapidly before diagnosis, reflecting the fast growth of these tumours. Most patients start experiencing symptoms very shortly before diagnosis. Because of the aggressive nature of DIPGs and the rate at which they grow, symptoms usually get worse quickly.

The most common symptoms at diagnosis include:

  • Double vision and/or one or two eyes turned in.
  • Difficulty in controlling eye and eyelid movement.
  • Facial paralysis, weakness, or drooping (usually one side).
  • Difficulty chewing and swallowing.
  • Difficulty speaking or slurred speech.
  • Difficulty with walking, balance and coordination due to weakness in the arms and legs.
  • Headaches (especially in the morning).
  • Nausea and vomiting.
  • Fatigue.
  • Problems urinating.

Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.

Diagnosis/diagnosing

Tests and procedures used to diagnose DIPG include a neurological exam and imaging tests. A biopsy may help confirm a diagnosis. Tests will vary depending on:

  • The type of tumour suspected.
  • Your child's signs and symptoms.
  • Your child's age and general health.

Neurological exam

During a neurological exam, your doctor will ask you about your signs and symptoms. They may check your vision, hearing, balance, coordination, strength and reflexes. Problems in one or more of these areas may provide clues about the part of your brain that could be affected by a brain tumour.

Imaging tests

Imaging tests and the location of the tumour in the pons will help your doctor diagnose. MRI is often used to diagnose brain tumours, and it may be used along with specialised MRI imaging, such as functional MRI, perfusion MRI and magnetic resonance spectroscopy. Other imaging tests may include a CT. 

Biopsy

Historically, biopsies were not able to be done on DIPGs. In recent years, studies have reported that biopsies can be safely done. Material from diagnosis may provide important biological information that may determine prognosis or help with the use of experimental chemotherapy.

Prognosis (Certain factors affect the prognosis and treatment options)

Unfortunately, the prognosis for DIPG remains very poor, although a small percentage of patients survive this disease. Brain tumours remain the most common cause of cancer-related death in children, and DIPG is the leading cause of death from pediatric brain tumours. 

A child diagnosed with DIPG today faces the same prognosis as a child diagnosed 40 years ago. There is still no effective treatment and no chance of survival. Only 10 per cent of children with DIPG survive for two years following their diagnosis, and less than one per cent survive for five years. The median survival time is nine months from diagnosis.

References

Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.