Stem cells are the blood making factories found within the bone marrow (contained in the soft cavities inside the bones). Stem cell transplants are used in the treatment of some cancers. Sometimes, they act as a rescue where high doses of chemotherapy have damaged the body’s own ability to generate blood-making cells. In other circumstances, they can help to trigger an immune response against cancer cells.
What are the types of stem cell transplants?
There are two types of transplants: autologous (using a patient's own cells) and allogeneic (using donor cells). In autologous transplants, the cells are harvested from the patient’s own blood. In allogenic transplants, donors' cells are taken from either bone marrow, umbilical cord blood, or circulating blood.
Why may a child or young person need one?
Stem cell transplants are used either as part of the treatment pathway depending on cancer type, where the patient has had a poor response to initial treatments, or in most cases, where there has been a relapse. Transplants are also used as the treatment where there are certain genetic markers that indicate this is appropriate.
Who can have one?
Having a stem cell transplant is influenced by a wide range of factors. There are some types of cancer where transplant will definitely be part of the treatment plan, and there are others where transplant is required because of a poor response to initial treatment or relapse. In the cases of allogenic transplants, there must be suitable donor options.
How are donors selected (allogenic only)?
We’re looking for a match based on human leukocyte antigens (HLA), a protein marker in our immune system. The best matches are siblings if available, followed by HLA-matched unrelated donors.
What are the different sources?
- Bone marrow: Where cells are taken directly from the bone marrow of the donor. This is done as a surgical procedure.
- Cord blood: Where a match has been found to donor cells in a cord blood bank where cells were taken at birth from an umbilical cord.
- Peripheral blood stem cells: The donor is given a drug to stimulate high volume of blood making cells to enter the peripheral blood. The blood is then harvested.
What does the process look like?
We check and record all organ functions and infection markers. These tests give us a good understanding of how everything is working ‘pre-transplant’ so that if anything changes, we can quickly detect and treat it.
We admit the child or young person to hospital and start isolation protocols. This is because they’ll be vulnerable to infection, and we treat in protected isolation. We need to make room in the bone marrow for the new cells, and this is done using chemotherapy and (or) radiation. This process effectively breaks down the patient’s own immune system – hence the need for isolation protocols. The exact conditioning process will be tailored to the patient with factors like age and cancer considered. Patients can expect to be prescribed many medications at this stage.
We infuse the stem cells around seven to 10 days after the conditioning treatment has started. The cells are infused through the central line, and the process is typically completed within a couple of hours.
This is when we can see that the new cells are beginning to function. This means the immune system is beginning to work and the blood making cells are active. We expect this will happen between two- and four-weeks post infusion. After this, it’s normal for isolation protocols to be relaxed.
By now, the patient has a new – but fragile – immune system. Patients should expect to be taking medications for a long period of time and will have frequent visits to the hospital. They won’t be able to get straight back to their old lives – there’ll be necessary restrictions and precautions until the new cells are at fully functional levels.
From Contact magazine issue 109 | Winter 2025
