A stem cell transplant is also known as a bone marrow transplant. This procedure may be recommended for children who have blood cancers, such as leukaemia, myeloma or lymphoma.
Stem cell transplants involve completely destroying all the blood-forming cells in your child’s bone marrow (including cancer cells) with high-dose chemotherapy or radiation therapy, and replacing them with healthy stem cells. These stem cells will develop into new, healthy bone marrow and produce healthy blood cells.
Stem cell transplants have four main phases:
- stem cell collection from your child or a donor, which can take 1–2 weeks
- transplant treatment (i.e. 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.
The total timeframe for a stem cell transplant is 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. Your child’s doctor will discuss with you the advantages and disadvantages of both types. It can be a complex decision that will depend on several factors, such as your child’s age and overall health, and any previous chemotherapy treatments.
In both types of transplant, the stem cells are given intravenously (i.e. through a vein). They will circulate in the body for about 1 day before settling in the bone marrow space and developing into new bone marrow.
Your child’s stem cells
Transplants that use your child’s own stem cells are called autologous transplants. In this process, 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 or radiation therapy to destroy their blood-forming cells. The frozen stem cells are then returned to their blood to make healthy new stem cells.
Although health professionals try to remove all the cancer cells from the stem cells before they are transplanted back, it is possible that the stem cells will still contain some cancer cells. This means that the cancer could come back after the transplant.
Stem cells from a donor
Transplants that use stem cells from a donor are called allogeneic transplants. In this process, 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.
Your child will have high-dose chemotherapy or radiation therapy to destroy their blood-forming cells, and then the donor’s stem cells will be given to your child.
The advantage of a transplant from a donor is that health professionals are more certain that the stem cells are all healthy. A transplant from a donor also creates a ‘new’ immune system (because the new white blood cells being made by the transplanted stem cells 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 your child’s body will ‘reject’ the new stem cells. This is known as ‘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
- 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 quite 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.