Diagnosing and Treating DIPG | Neurological Surgery

The brainstem consists of three parts: The midbrain, the pons, and the medulla oblongata. DIPG is a pontine glioma, meaning that it develops in the pons.

Unlike tumors at other locations, a tumor in the pontine segment of the brainstem is not often biopsied; however, with biopsies being safe, they can be performed in cases of diagnostic uncertainty. Diffuse intrinsic pontine glioma (DIPG) is usually diagnosed based on the patient’s symptoms and magnetic resonance imaging (MRI) studies. MRI scans produce detailed images of the brain and allow doctors to detect the presence of a tumor. Sometimes the patient is also given a contrast agent (a special dye) before the scan to help doctors better tell whether the abnormal tissue is a tumor and what type of tumor it is. The location in the pons, the way it infiltrates nearby tissue, and the lack of clear borders of the tumor all signify that a tumor is likely DIPG.

If the child’s symptoms and the MRI images are not typical, a stereotactic biopsy may be required to make a diagnosis. In this case, a small hole is drilled in the skull and a needle is passed through the hole to take a small piece of tissue for testing. A pathologist will examine the sample and make a diagnosis. Today, the presence of specific molecular markers is also investigated, as it can affect prognosis or enrollment in specific clinical trials.

Treatment for DIPG
Although surgical resection is the treatment of choice for many other types of brain tumors, it is not considered a treatment option for children with DIPG. The tumor infiltrates so extensively into normal brain tissue, and the brainstem carries out such critical functions (like controlling breathing), that surgical removal of the tumor is impossible. Chemotherapy has not been proven effective, at least in part because anti-cancer drugs cannot cross the blood-brain barrier and reach the tumor in sufficient amounts.

Radiation therapy is the primary treatment for DIPG. Radiation therapy helps shrink the tumor and reduces pressure on the brain. This is typically performed as five daily sessions per week for a total of 30 to 33 sessions. This treatment can alleviate symptoms quickly and hold the cancer at bay for about six months on average. When the tumor comes back, repeat radiation therapy is an option. Repeat radiation therapy is usually done with five daily sessions (but the dose per session is different from that of initial radiation therapy) per week for 10 sessions.

There are a number of clinical trials for DIPG. One potential new treatment that was tested at Weill Cornell Medicine Pediatric Neurosurgery and Memorial Sloan-Kettering involved the delivery of an anti-cancer agent directly to the tumor. Injecting this targeted radio-immunotherapeutic drug directly into the tumor avoids intruding on delicate brain stem tissue and eliminates the need for medicine to cross the blood-brain barrier. Dr. Souweidane published the results of this Phase 1 trial, and you can see his results here.

Find out more about the clinical trial.

Find out more about the Children’s Brain Tumor Project.

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