Radioation Therapy

From the Children's Neuroblastoma Cancer Foundation website

Neuroblastoma Radiation Therapy

Radiation therapy uses high-energy rays or particles to kill cancer cells. Radiation is sometimes a necessary part of treatment, but because of the possible long-term side effects in children, it is avoided when possible. Two types of radiation therapy can be used to treat children with neuroblastoma.

External Beam Radiation Therapy
This type of radiation therapy focuses radiation on the cancer from a source outside the body. There are several situations in which this type of radiation therapy might be used: 
  • To destroy neuroblastoma cells that remain behind after surgery and chemotherapy
  • To try to shrink tumors before surgery, making them easier to remove at the time of surgery
  • To treat larger tumors that are causing serious problems (such as trouble breathing) and do not respond quickly to chemotherapy
  • As part of the treatment regimen (along with high-dose chemotherapy) before a stem cell transplant in children with high-risk neuroblastoma
  • To help relieve pain caused by advanced neuroblastoma
The radiation is typically directed at the tumor itself, but in some cases it may also target other parts of the body to reduce the risk of cancer spread. When radiation is delivered throughout the body, it is known as total body irradiation (TBI). External radiation therapy is much like getting an x-ray, but the radiation is more intense. The procedure itself is painless. 

Before treatments start, the radiation team takes careful measurements with imaging tests such as MRI scans to determine the correct angles for aiming the radiation beams and the proper dose of radiation. Each actual treatment lasts only a few minutes, but the setup time – getting your child into place for treatment – usually takes longer. Young children may be given medication to make them fall asleep so they will not move during the treatment. Most often, radiation treatments are given 5 days a week for several weeks. 

Possible Side Effects Short-term side effects of external radiation therapy may include mild skin reactions, nausea, diarrhea, or fatigue. Often these go away after a short while. Talk with your child’s doctor about these side effects because there are ways to relieve some of them. Radiation may also make the side effects of chemotherapy worse. 
Radiation therapy can interfere with the growth of normal body tissues, and may increase the risk of developing other cancers later on. The actual effects depend on the part of the body getting radiation. 

MIBG radiotherapy

MIBG is a chemical similar to norepinephrine, which is made by sympathetic nerve cells. A slightly radioactive form of MIBG is sometimes injected into the bloodstream as part of an imaging test to look for neuroblastoma cells in the body. 

A more highly radioactive form of MIBG is also used to treat some patients with advanced neuroblastoma, often along with other treatments. Once injected into the bloodstream, the MIBG goes to the sites of tumors anywhere in the body, where it delivers its radiation. The child will need to stay in a special room for a few days after the injection until most of the radiation has left the body. 

Possible Side Effects
MIBG therapy can sometimes cause nausea and vomiting. It can also lower blood cell counts because of its effects on the bone marrow. In rare cases it may cause high blood pressure for a short period of time. MIBG may build up in the thyroid gland in the neck, which can sometimes result in low levels of thyroid hormone in the body.

Once the treatment fields are set, the radiation oncologist will mark the corners of the fields with small tattoos or a special pen (markings are usually no bigger than the head of a pin or a freckle). The marking is a guide to help the technician line up the radiation treatment fields the same way each time you receive treatment.

Most cancer centres today recommend that people have tattoo markings for radiation therapy rather than ink markings, because the ink can fade or wash off. While tattoos can be removed after treatment is over, they are also preferred over ink markings made with a pen because are that they permanently mark the area of the original treatment field in case radiation is needed in the future.

Tattoo markings are done with a very small needle and drop of ink. Some patients may feel a small pinch, like an insect bite, while the markings are being created. A tattoo marking will have the appearance of a dark freckle.

Neuroblastoma High-Dose Chemotherapy/Radiation Therapy and Stem Cell Transplant

This type of treatment is used in children with high-risk neuroblastoma who are unlikely to be cured with other treatments. It involves giving high doses of chemotherapy (higher than could safely given otherwise) and/or radiation therapy (total body irradiation or high-dose MIBG), and then replacing the body’s bone marrow cells, which were killed by the treatment. In the past, this type of treatment was commonly referred to as a bone marrow transplant. 

The bone marrow is the soft, inner part of some bones where new red blood cells, white blood cells, and platelets are formed. Red blood cells carry oxygen to all parts of the body. White blood cells are part of the immune system, which fights off infections. Platelets are needed to stop bleeding caused by cuts and scrapes. 

Both chemotherapy and some types of radiation can affect blood-forming stem cells in the bone marrow. (These are the cells that make the different types of blood cells.) Even though more intensive treatments might be more effective in treating tumors, they can’t be given because they would cause severe damage to the bone marrow, leading to life-threatening shortages of blood cells. 

Doctors try to get around this problem by giving the child an infusion of blood-forming stem cells after treatment. This is known as a peripheral blood stem cell transplant (PBSCT). 

What It Involves
The first step in a PBSCT is to collect, or “harvest,” the child’s own blood-producing stem cells to use later. In the past, the stem cells were often taken from the child’s bone marrow, which was done by drilling small holes in certain bones. But doctors have found that these cells can be taken from the bloodstream during a procedure known as apheresis. This is similar to donating blood, but instead of going into a collecting bag, the blood goes into a special machine that filters out the stem cells and returns the other parts of the blood back to the person’s body. The stem cells are then frozen until the transplant. 

After the harvest, the child gets high-dose chemotherapy and/or radiation. When treatment is complete, the patient’s stem cells are thawed and returned to the body in a process similar to a normal blood transfusion. The stem cells travel through the bloodstream and settle in the bone marrow. Over the next 3 or 4 weeks, the stem cells start to make new, healthy blood cells in the child’s bone marrow. 

Until this happens, the child is at high risk of infection because of a low white blood cell count, as well as bleeding because of a low platelet count. To avoid infection, protective measures are taken, such as using special air filters in the hospital room and having visitors wear protective clothing. Blood and platelet transfusions and treatment with IV antibiotics may also be used to prevent or treat infections or bleeding problems. 

A peripheral blood stem cell transplant is a complex treatment. If the doctors think your child may benefit from a transplant, the best place to have this done is at a nationally recognized cancer center where the staff has experience in performing the procedure and managing the recovery period. 

A stem cell transplant is also very expensive and often requires a lengthy hospital stay. Because the procedure is so expensive, you should have an idea of how the costs might be covered beforehand. Be sure to get a written approval from your insurer if the procedure is recommended for your child. 

Possible Side effects
Possible early complications and side effects are basically the same as those caused by any other type of high-dose chemotherapy or radiation therapy, and are due to damage to the bone marrow and other quickly dividing tissues of the body. They can include low blood cell counts (with increased risk of infection and bleeding), nausea, vomiting, loss of appetite, mouth sores, and hair loss. 

One of the most common and serious short-term effects is an increased risk for infection. Antibiotics are often given to try to prevent this from happening. Other side effects, like low red blood cell and platelet counts, may require blood product transfusions or other treatments. 

Some complications and side effects can persist for a long time or may not occur until years after the transplant. Be sure to talk to your child’s doctor before the transplant to learn about possible long-term effects your child may have. 

The most recent and exciting advancements in cancer treatment involve the use of Immunotherapies. Monoclonal antibodies are man-made versions of immune system proteins that can be programmed to attack a very specific target. These molecules can be injected into the body to seek out and attach to cancer cells. A monoclonal antibody called ch14.18 has been developed to attach to the ganglioside GD2, a substance found on the surface of many neuroblastoma cells. This antibody is often given together with cytokines (immune system hormones) such as GM-CSF and interleukin-2. This combination can help the child's immune system to recognize and destroy neuroblastoma cells. 
This antibody is now part of the routine treatment for many children with high-risk neuroblastoma, often after a stem cell transplant. 

Possible Side effects
Side effects from immunotherapy may include pain, buildup of fluid in the body and allergic reactions.