Stem cell transplants – the lowdown

Hematopoietic stem cells (often just called stem cells) are very early blood cells, which mature into full blood cells. They are found in bone marrow, the spongey material inside bones.¹

A stem cell transplant is a treatment where bone marrow containing CML cells is replaced by stem cells, which develop into healthy bone marrow and blood cells. This creates a new immune system, and the transplanted cells can also help attack any remaining CML cells.¹

The healthy stem cells are taken from a donor, whose cells are very similar to yours – often a close relative, although they may come from an unrelated donor from a register. This is known as an allogeneic stem cell transplant.¹

For many people, TKIs can control CML very well for a long time and so treatment with TKIs have largely replaced stem cell transplants. And taking a TKI is usually less stressful on your body than having a transplant. There are different TKIs, so your doctor will usually try you on another one if the medicine you’ve been taking stops working. But if that doesn’t work either, they may consider a stem cell transplant.²

Here we answer some FAQs:

• What is involved in an allogeneic stem cell transplant?
  Once your potential donor is found, your doctor will organise a special blood test called Human Leukocyte Antigen (HLA) typing to check the donor and tissue type are a match.¹ The donor’s stem cells are then collected from their blood, or sometimes from their bone marrow in a procedure at the hospital. Before the transplant, you will receive chemotherapy and sometimes whole-body radiotherapy to kill the CML cells in your blood and the stem cells in your bone marrow, making room for the healthy stem cells. It also weakens your immune system, so your body doesn’t attack the donor stem cells.¹ You’ll then have the new stem cells through a drip in your vein to replace your own stem cells. Eventually, your body takes over and continues to produce its own stem cells, bone marrow and blood cells. You may need to stay in hospital in isolation while your immune system recovers and be given antibiotics to prevent infection.¹ You may feel tired and weak while waiting for your body to make new blood cells – but you’ll feel better once this starts happening, after a few weeks.³
• Will I need to take any long-term treatments after the transplant?¹
  Your doctor will test your blood or bone marrow for the BCR-ABL1 protein transcript to check if the transplant worked. This test is called the qPCR. If the levels of this gene are low enough, the transplant is considered successful. They will continue to check your blood or bone marrow every few months for the next few years. Your doctor may put you on a TKI for 1 year after the transplant, as this may help to stop the CML coming back. If the transplant hasn’t worked, or your CML has worsened since the transplant, there are a few options your doctor may discuss with you. One option may be to take another TKI, sometimes as well as having a procedure called Donor Lymphocyte Infusion (DLI), where you receive lymphocytes from the same person who donated their stem cells to you. If two or more TKIs didn’t work – they may suggest another round of a different type of chemotherapy.
• What are the risks?
  Chemotherapy can have serious side effects such as sickness and a higher risk of infection. So your healthcare team will make sure you can cope emotionally and physically with a transplant. There can be a higher risk of a side effect called graft versus host disease (GvHD) with a stem cell transplant. This is where healthy donor cells attack your own body’s cells. If it’s mild, it can actually be helpful as it may kill off any remaining CML cells. But if severe, it can be dangerous. Stem cell transplants may cure CML or at least manage it for a long time. But a stem cell transplant is a demanding treatment that can be tough on your body, so your doctors will look at your overall health and your phase of CML before they decide to give you a transplant. For more about your CML treatment see Understanding treatments for CML.

1. NCCN Guidelines for Patients. Chronic Myeloid Leukemia, 2018.
2. Barrett, J and Sawa, I. 2015. Blood. 125(21): 3230–3235.

3. Cancer.net. What is a Stem Cell Transplant (Bone Marrow Transplant)?. Accessed May 2018.

4. CML Support. Stem Cell Transplantation. Accessed May 2018.

5. Cancer.net. Leukemia - Chronic Myeloid - CML: Treatment Options. Accessed May 2018.