DIPG / DMG Biopsies

Diffuse intrinsic pontine glioma and diffuse midline glioma (DIPG/DMG) are highly aggressive forms of brain cancer that occur in children. They are located in the pons, a part of the brainstem that controls many vital functions such as breathing and heartbeat. Unfortunately, DIPG/DMG has a very poor prognosis, with a five-year survival rate of less than 10%. Despite advances in treatment, there is still no cure for this devastating disease. Biopsies are a critical component of DIPG/DMG diagnosis and management, providing valuable information that can help guide treatment decisions.

What is a DIPG / DMG biopsy?

A biopsy is a medical procedure that involves taking a small sample of tissue from the body for examination under a microscope. In the case of DIPG/DMG, a biopsy involves taking a sample of the tumor tissue from the pons. This procedure is typically performed using a stereotactic biopsy technique, which involves using imaging guidance to precisely target the tumor tissue.

Stereotactic Biopsy

A stereotactic biopsy is based on obtaining a computerized image on which a target (tumor) can be identified; that image can be an MRI or CT scan. Technology is then used to calculate the position of the target in relation to the scan. Several different technologies are available to do that, some using a rigid frame that is attached to the head before the scan, and others that can map the surface of the face and use that as the basis for determining the tumor’s position. With the head in a fixed position and the trajectory calculated, a very small hole is made in the skull to allow the needle to pass to the target and obtain the tissue. The tissue is then removed and prepared so as to identify the pathology; other studies may also be done. Stereotactic biopsy has the advantage of a very small incision, a small hole in the bone, and less risk than a larger open operation.

Most studies of stereotactic biopsy have shown relatively little damage as a result and a very low rate of death from the procedure (less than 1%).

Why are DIPG / DMG biopsies important?

DIPG/DMG is a highly heterogeneous disease, meaning that it can vary greatly from patient to patient. Biopsies provide critical information about the specific molecular and genetic characteristics of a patient's tumor, which can help guide treatment decisions. For example, some DIPG/DMG tumors may have mutations in certain genes that make them more responsive to particular types of drugs. By identifying these mutations, doctors can tailor treatment to the specific needs of each patient, potentially improving outcomes.

In addition to providing information about the molecular and genetic characteristics of the tumor, biopsies can also help rule out other types of brain tumors that may have similar symptoms to DIPG/DMG. This is important because some of these other tumors may be more responsive to treatment, and a misdiagnosis could result in the wrong treatment being given.

What are the risks of a DIPG / DMG biopsy?

As with any medical procedure, there are risks associated with a DIPG/DMG biopsy. The most significant risk is that the procedure can cause damage to the brainstem, which can result in neurological deficits such as weakness, paralysis, or speech problems. There is also a risk of bleeding, infection, and other complications.

Due to the potential risks, doctors must carefully consider whether a biopsy is appropriate for each patient. In some cases, a biopsy may not be recommended if the risks outweigh the potential benefits.

What happens after a DIPG / DMG biopsy?

The results of a DIPG/DMG biopsy can take several days or weeks to come back, depending on the complexity of the analysis. Once the results are available, doctors will use them to guide treatment decisions.

In some cases, the biopsy may reveal that the tumor is inoperable or that the risks of further treatment outweigh the potential benefits. In these cases, doctors may recommend palliative care to help manage symptoms and improve quality of life.

For patients with operable tumors, the biopsy results will guide the choice of treatment. This may involve radiation therapy, chemotherapy, or a combination of both. The specific treatment plan will depend on the molecular and genetic characteristics of the tumor and the patient's individual circumstances.

In some cases, clinical trials may also be available as a treatment option. These trials may involve testing new drugs or therapies that are not yet available to the general public. Patients who participate in clinical trials may have access to cutting-edge treatments that could potentially improve outcomes.

It is important to note that DIPG/DMG is a highly aggressive disease, and even with the best available treatments, outcomes can be poor. However, biopsies might provide critical information that can help doctors make more informed treatment decisions and potentially improve outcomes for patients.

In addition to guiding treatment decisions, biopsies also play an important role in research efforts aimed at developing new treatments for DIPG/DMG. By studying the molecular and genetic characteristics of DIPG/DMG tumors, researchers can identify new targets for drug development and test new therapies in preclinical and clinical trials.

What about liquid biopsies?

DIPG/DMG blood or cerebrospinal fluid biopsies involve taking a small sample of blood or a sample of spinal fluid (via a spinal tap) from a patient with DIPG/DMG and analyzing the DNA of the cancer cells that are shed into that fluid. These cancer cells are known as circulating tumor cells (CTCs) and can provide valuable information about the genetic makeup of the tumor.

The analysis of CTCs can reveal important information about the tumor's mutations, which can help doctors to choose the most effective treatment for the patient.

How do DIPG / DMG blood biopsies work?

DIPG/DMG biopsies from blood or spinal fluid are a relatively new technologies that are still being developed and refined.  The process involves extracting the DNA from a patient's blood sample and analyzing it for the presence of DIPG/DMG mutations. This technique can be used to detect genetic changes in the tumor.

Potential benefits of DIPG / DMG blood or spinal fluid biopsies

DIPG/DMG blood or spinal fluid biopsies have the potential to revolutionize the diagnosis and treatment of DIPG/DMG. Here are some potential benefits of this approach:

  1. Early detection: DIPG/DMG blood biopsies may allow for earlier detection of the disease, which can improve the chances of successful treatment.
  2. Personalized treatment: By analyzing the genetic mutations of the tumor, DIPG/DMG blood biopsies can help doctors to choose the most effective treatment for each patient.
  3. Non-invasive monitoring: DIPG/DMG blood biopsies can be used to monitor the tumor's response to treatment without the need for invasive procedures such as surgery.
  4. Better understanding of the disease: DIPG/DMG blood biopsies can provide valuable insights into the genetic makeup of DIPG/DMG, which can help researchers to develop new treatments and therapies.

Challenges and limitations of DIPG / DMG blood or spinal fluid biopsies

Despite their potential benefits, there are several challenges and limitations associated with DIPG/DMG blood biopsies. Here are some of the main issues:

  1. Accuracy: DIPG/DMG blood biopsies may not always provide accurate results due to the low levels of CTCs in the bloodstream.
  2. Availability: DIPG/DMG blood biopsies are not yet widely available and are currently only available through clinical trials or specialized research centers.
  3. Cost: The cost of DIPG/DMG blood or spinal fluid biopsies may be high, which could limit their accessibility for some patients.
  4. Technical challenges: The isolation and analysis of CTCs can be technically challenging, and there is a risk of contamination or loss of CTCs during the process.
  5. Ethical considerations: There are ethical considerations associated with the use of DIPG/DMG blood or spinal fluid biopsies, including concerns about privacy, consent, and the potential psychological impact on patients and families.

DIPG/DMG blood and spinal fluid biopsies and conventional biopsies have the potential to improve the diagnosis and treatment of DIPG/DMG. By analyzing the genetic makeup of DIPG/DMG tumors CTCs, doctors might be able to offer more personalized and effective treatment options for patients, as well as monitor their response to treatment.