Immunotherapy for Brain Tumors in Children

Immunotherapy is the use of medicines to help a person’s own immune system recognize and destroy cancer cells. Immunotherapies are being used and studied to treat some types of brain tumors in children.

PD-1 inhibitors

PD-1 is a checkpoint protein on immune cells called T cells. PD-1 normally acts as an “off switch” to help keep T cells from attacking normal cells. Drugs that block this protein may allow the immune system to see the cancer cells and destroy them. Examples of PD-1 inhibitors include:

• Nivolumab
• Pembrolizumab

CTLA-4 inhibitors

CTLA-4 is another checkpoint protein on some T cells that acts as an “off switch” to keep the immune system from attacking normal cells. Some cancers use this protein to escape the immune system. When these drugs are used to block CTLA-4, they allow the immune system to see the cancer cells and destroy them. Ipilimumab is an example of a CTLA-4 inhibitor. It’s being studied in combination with nivolumab to treat INI-negative tumors, such as atypical teratoid rhabdoid tumors (ATRT), in clinical trials.

Side effects of checkpoint inhibitors

To learn more about the side effects of immune checkpoint inhibitors, see Immune Checkpoint Inhibitors and Their Side Effects.

Immunotherapies under investigation

While some immunotherapies may sometimes be used outside of a clinical trial, the treatments below are still considered experimental for brain tumors. At this time, they are available only through clinical trials.

Chimeric antigen receptor (CAR) T-cell therapy

For this treatment, immune cells called T cells are removed from the child’s blood through an IV line that goes into a machine during a process called leukapheresis. The remaining blood then goes back into the body. This typically takes a few hours, and it might need to be repeated.

The T cells are then genetically altered in the lab to have specific receptors, called chimeric antigen receptors (CARs), on their surface. These receptors can attach to proteins on cancer cells. The T cells are then multiplied in the lab and given back into the child’s blood where they can seek out the cancer cells and attack them. This process can take a few weeks.

For the treatment itself, the CAR T cells are infused either into a vein or into the cerebrospinal fluid (CSF) through a reservoir, such as an Ommaya. This may be done with or without chemotherapy, depending on the treatment plan.

This approach has been successful in treating childhood leukemias (blood cancers). Researchers are studying whether this type of treatment may be useful in children with other types of cancer, such as brain tumors, in clinical trials.

Cancer vaccines

Several types of vaccines are being developed against brain tumor cells. Unlike vaccines against infectious diseases, these vaccines are meant to help treat the disease instead of prevent it. The goal of these vaccines is to stimulate the body’s immune system to attack brain tumor cells.

Early study results for some of these vaccines have shown promise, but more research is needed to determine how effective they are. At this time, brain tumor vaccines are available only through clinical trials.

Therapeutic viruses

Researchers have done a great deal of lab work with viruses that reproduce only within brain tumor cells and then cause those cells to die, while leaving normal cells alone. Research using these viruses in humans with brain tumors is still in very early stages.