Stem cell transplant
A stem cell transplant is also known as a bone marrow transplant. Your child's doctor may recommend this treatment if your child has a blood cancer, such as leukaemia, lymphoma, or high-risk neuroblastoma.
Stem cell transplants involve completely destroying all the blood-forming cells in your child's bone marrow. This includes cancer cells. High-dose chemotherapy or radiation therapy is used for this. Then, all the blood-forming cells are replaced with healthy stem cells. These stem cells will develop into new, healthy bone marrow and produce healthy blood cells.
Stem cell transplants have 4 main phases:
- stem cell collection from your child or a donor, which can take 1–2 weeks
- chemotherapy and/or radiation therapy, to destroy all the cells in your child's bone marrow, which can take about 1 week
- stem cell infusion, which happens in 1 day
- recovery, which can take 2–12 weeks, depending on the type of treatment.
A stem cell transplant takes about 4–14 weeks.
Types of stem cell transplant
A stem cell transplant can use either your child’s own stem cells or stem cells from a donor. The choice of whether to use your child’s own cells or stem cells from a donor depends on the type of cancer being treated.
In both types of transplant, the stem cells are given through a vein (intravenously). They will circulate in the body for about 1 day. They will then settle in the bone marrow space and become new bone marrow.
Your child's stem cells
Transplants that use your child's own stem cells are called autologous transplants.
This involves 3 main steps:
- Some of your child's stem cells are collected from their blood or bone marrow and frozen for later.
- Your child is then given high-dose chemotherapy to destroy their blood-forming cells and any remaining cancer cells.
- The frozen stem cells are then returned to their blood to make healthy new stem cells.
Stem cells from a donor
Transplants that use stem cells from a donor are called allogeneic transplants.
This involves 3 main steps:
- Another person donates their stem cells to your child. The donor is usually a sibling or other close family member whose tissue type is nearly identical to your child's. Sometimes, an unrelated volunteer donor will match your child's tissue type. In some cases, the stem cells can come from umbilical cord blood collected from unrelated healthy newborn babies.
- Your child will have high-dose chemotherapy or radiation therapy to destroy their blood-forming cells.
- The donor's stem cells will be given to your child and make healthy stem cells.
A transplant from a donor has 2 main advantages:
- The doctors are more sure that the new stem cells are all healthy.
- A transplant from a donor also creates a ‘new' immune system. This is because the new white blood cells that the transplanted stem cells are making are different from your child's original white blood cells. The ‘new' immune system can continue fighting the cancer even after the radiation therapy and chemotherapy finish. This is called a ‘graft-versus-tumour effect' and works very well with some types of cancer.
The disadvantage of a transplant from a donor is the risk that the new stem cells will react against your child's body. This is called ‘graft-versus-host disease' (GVHD) and can be very serious. Your child might be given anti-rejection medication for the first few months after the transplant to reduce the risk of GVHD.
The recovery period for a transplant from a donor is usually longer than for a transplant using your child's own stem cells.
Side effects of stem cell transplants
Side effects of stem cell transplants can include:
- increased risk of infection – your child will be very prone to infections because the transplant treatment completely destroys their blood-forming cells, and therefore destroys their immune system. The risk of infection is mainly during the first month after the transplant. The infection risk decreases when the new marrow starts making normal numbers of infection-fighting white blood cells.
- graft-versus-host disease (GVHD) – this can only happen for children who have received stem cells from a donor. Because the stem cells are from another person, the stem cells may recognise your child's body as ‘foreign' and attack your child's cells. In severe cases, this can be life-threatening. However, in a mild or moderate form, it actually helps to fight the cancer. If necessary, GVHD can be treated with anti-rejection medicines
- other side effects as a result of the transplant treatment (see Side effects of chemotherapy and Side effects of radiation therapy).
Cancer treatments affect each person differently – your child may experience none, some or many of these problems.
Medicines and other treatments are available to help deal with many of these side effects. Your child's doctor will discuss these with you.
Some of these side effects seem severe and can be very distressing for you and your child. However, the benefits of stem cell transplants usually outweigh the risks. Your child's doctor will discuss the risks and benefits with you.