What is an allogeneic stem cell transplant?
Allogeneic stem cell transplant is a procedure that transfers healthy donated stem cells to a patient whose own cells have been destroyed by radiation or chemotherapy.
'Allo' in allogeneic means the stem cells come from an 'other' person. The donor stem cells must have a genetic typing that matches the recipient's. Usually, donors come from a direct relation (such as a sibling).
If there is no familial match, compatible donors may be found through international bone marrow registries. Special blood tests are done to check for donor-recipient compatibility.
Stem cells can also come from the blood from the umbilical cords of newborns (cord blood) that has been stored. This type of treatment is mainly used for children as the number of stem cells in cord blood is not enough to treat adults.
Allogeneic vs autologous stem cell transplant
In an allogeneic stem cell transplant, you receive stem cells donated by someone else. In contrast, an autologous stem cell transplant uses our own cells, which means you are your own donor.
In this type of transplant, your stem cells are harvested (removed), frozen and stored before you receive your high-dose chemotherapy or radiation therapy treatment. After your treatment, your stem cells are thawed and returned back into you.
Why do you need an allogeneic stem cell transplant?
Allogeneic stem cell transplants are used to treat conditions such as:
- Hodgkin lymphoma
- Multiple myeloma
- Myelodysplastic syndrome
- Non-Hodgkin lymphoma
- Severe aplastic anaemia
- Testicular cancer
The advantages include the following:
- The donor stem cells produce their own immune cells, which may help destroy the cancer cells that remain after high-dose treatment.
- The donor can be recalled to donate more stem cells if needed.
The disadvantages include the following:
- The donor cells may be more likely to die or be destroyed by the recipient’s immune system before settling in the bone marrow.
- The donor cells may create new immune cells that attack the recipient’s body, a condition known as graft-versus-host disease (GvHD).
- A small risk of infections from the donor cells (although donors are tested beforehand to minimise this risk).
What are the risks and complications of an allogeneic stem cell transplant?
The side effects of a stem cell transplant may vary from person to person. Some individuals experience multiple side effects, while others may have fewer. Some side effects are short-term (acute), while others are long-term (chronic).
Many of the side effects result from the chemotherapy or radiation therapy given before the transplant. Others are related to the stem cell transplant.
Initial side effects can include:
- Mouth and throat pain
- Nausea and vomiting
- Bacterial, viral or fungal infections
- Bleeding and anaemia (low red blood cell count)
- Graft-versus-host disease (GVHD), which happens when the donor immune cells see your body as foreign and the cells attack certain organs
- Lung problems such as pneumonitis, an inflammation of lung tissue
- Veno-occlusive disease (VOD), when small blood vessels that lead to the liver become blocked
Longer-term side effects can include:
- Eye problems such as cataracts
- Organ damage
- Return of the cancer
- Secondary cancers
- Lymph tissue problems
- Thyroid problems caused by hormone changes
After your stem cell transplant, your doctor will monitor you closely. They will take measures to prevent side effects and to quickly deal with any that develop.
What can you expect in anallogeneic stem cell transplant?
You will need to undergo conditioning therapy in preparation for the stem cell transplant.
Conditioning therapy is used to:
- Remove any remaining cancer cells left in the body
- Prepare your bone marrow to receive the donor stem cells
- Suppress your immune system to lower the chance of rejecting the donor stem cells
Conditioning includes myeloablative therapy, where you will be given high doses of chemotherapy through a central venous catheter (tube). You may also require total body irradiation (TBI), a form of radiation therapy in which the whole body is treated with radiation. The treatment plan will vary depending on the disease being treated.
The treatment is usually given over a few days.
Stem cells transplant
The transplant is usually done 1 – 3 days after the end of conditioning therapy. The day of the transplant is usually referred to as day 0.
You will be given the stem cells through a central venous catheter. The number of stem cells you receive is calculated based on your weight.
The duration of the transplant depends on the number of stem cells given. It usually takes about 1 – 2 hours.
You will be monitored closely for any side effects while you are receiving the stem cells. Side effects could include chills, fever, chest pain, headache, nausea, shortness of breath and hives.
After the procedure
After the procedure, the transplanted stem cells enter the blood and make their way to the bone marrow to start making new blood cells. This process is known as engraftment.
It may take 2 – 6 weeks before your blood cell counts return to normal.
During this time, you may need to stay in an isolated room in the hospital due to the increased risk of infection. You may:
- Feel tired and generally unwell
- Have to take daily blood tests and regular temperature checks
- Be watched closely for bleeding, nausea, vomiting, diarrhoea and any other reactions
- Be given medicine including antibiotics, antifungals and antivirals to prevent and treat infections
- Be given nutrition and supplements through a central venous catheter until you are ready to eat by mouth
- Be given colony-stimulating factors (CSF) to speed up the healing
- Need blood transfusions and platelet transfusions
You will only be discharged from the hospital if you:
- Have not had a fever for 24 – 48 hours
- Have been able to take medication and keep it down for 48 hours
- Are able to control your symptoms such as nausea, vomiting and diarrhoea with medication
- Are able to eat food and drink enough fluids
- Have safe levels of blood cell counts
- Have a caregiver at home to assist you during your recovery
Care and recovery after an allogeneic stem cell transplant
Your recovery process may take several months or longer. During this period you may not be able to return to work or resume your previous lifestyle.
You will be at risk of infections for the next 1 - 2 years as it takes a while for your immune system to return to full strength.
During the recovery period, you will have to attend follow-up appointments with your doctor to check on your health and progress.