Pediatric brain tumors (PBTs), are the second most common childhood cancer.
Typical signs of of brain tumors in children are:
- Headaches that may be worse in the morning and get better during the day.
- Nausea or vomiting in the morning.
- Problems with motor skills, such as clumsiness or poor handwriting.
- Tilting of the head to one side.
- Walking difficulty and balance problems.
In general, pediatric brain tumors are treated with either surgery, chemotherapy for brain tumors in children or radiation therapy, or through or a combination of the three.
Generally, there is a specific type of oncologist, known as a radiation oncologist, that carries out this therapy. Radiation is administered at various times, which is left up to the discretion of the doctor. For pediatric brain tumors, it can be used in three scenarios:
- First, it can be used to destroy the remaining cells that exist after the resection or the removal of the tumor.
- Secondly, surgery is often not the ideal option if the tumor is located in a part of the brain that is too sensitive to be touched and therefore, radiation therapy can then be administered.
- Lastly, it can be used to help prevent symptoms that would result from a tumor .
Radiation therapy can have aggressive long-term side effects, particularly on the developing brains of little children. Radiation can lead to long-term neurocognitive deficits, even in older children. While the doctor will try to administer just enough radiation to affect the tumor and not the rest of the brain, that can be difficult and there is often spillover into normal areas of the brain.
Before the start of any radiation therapy treatment regimen, the radiation team convenes to measure the appropriate angles that are necessary for the perfect aim of the beam as well as the correct dose. Often, children may be fitted for a body cast in order to keep them still during the procedure so that there are no accidents in the radiation beam angle. Usually, the radiation therapy sessions only last 15-30 minutes, but much of that time may be spent adjusting the children into their position and the actual radiation takes much less time. Radiation is conducted as the child lies on a table with a machine aimed at the head. Radiation therapy is administered on a weekly schedule, generally from Monday to Friday.
There are a few different types of radiation therapy with their own advantages and disadvantages. It is up to the discretion of the oncologist for which radiation is appropriate .
One of the more common types of radiation therapy is 3D-CRT, or three-dimensional conformal radiation therapy. This technique uses imaging tests such as MRIs to determine the correct location of the tumor. Upon recognizing the location, many x-ray beams are aimed at the tumor from various directions, with each beam being relatively weak. This technique has the advantage of causing less damage to normal tissue but since the individual beams converge onto the tumor, they are able to deliver intense radiation at the spot .
Another type of radiation therapy is IMRT, or intensity modulated radiation therapy, which is a more innovative form of the prior mentioned 3D-CRT. While the basic technique remains the same with multiple weak beams converging onto the tumor, their individual intensities can be adjusted so that there is less radiation affecting the most sensitive brain tissue. This technique has become increasingly popular and is now used in most hospitals .
Another method of radiation therapy is called conformal proton beam radiation therapy. This technique is similar to 3D-CRT, however, instead of the use of x-rays, this technique uses proton beams on the tumor. The advantage of this therapy, as opposed to 3D-CRT, is that the x-rays release energy before and after they hit their target, which causes damage of normal brain tissue along the way. However, protons only release their energy after they have traveled a specified distance, and therefore cause little damage to normal tissue. This allows oncologists to send more radiation directly to the tumor with less damage along the way.
However, while in theory it is more advantageous, a lot of tumors don’t have distinct edges and can blend in with normal tissue, which makes it difficult to estimate the correct distance to deliver the proton therapy to. Thus, it useful for tumors such as chordomas but not for tumors like glioblastomas. There are only a few centers in the US that use proton beams .
Sterotactic radiotherapy is a technique which uses a large dose of radiation and delivers it to the tumor in just a few radiotherapy sessions. This is used in only in few specific scenarios such as if a child is too weak to undergo surgery .
Another method is brachytherapy, which is different from others as it puts the radiation source directly into the tumor or near it, and therefore the radiation only goes a small distance. This is often used along with a low dose of external radiation .
Finally, there is whole brain and spinal cord radiation therapy, which is conducted if MRIs show that the tumor has spread to the covering of the spinal cord or to the CSF, and therefore the radiation has to be spread out enough to cover those areas .
Radiation therapy is an aggressive way of treating patients with pediatric brain tumors but sometimes an unavoidable method. There has been innovation over the past few years in this area and radiation has become less damaging to surrounding tissues but unfortunately, it still remains dangerous to the developing brain and should be avoided in children less than three years of age.