In an allogeneic transplant, stem cells are donated to the person from another person, a genetically matched stem cell donor. This is usually a family member, a brother or sister with the same tissue type. Where no sibling is available, a search is made to find the donors. Sometimes there is a slight mismatch between the tissue type of the donor (usually a family member) and the person, but they may still be the best possible match.
An allogeneic transplant offers the best chance of curing a number of blood cancers and other serious diseases. These include: leukaemia, some types of lymphoma, myeloma, myelodysplastic syndromes, aplastic anaemia and other rare bone marrow diseases.
Stem Cell Collection:
The donor has to undergo a series of injections called Granulocyte Colony Stimulating Factor (G-CSF) (usually four doses given over four days) to stimulate the stem cells to enter the blood stream. Once the Peripheral Blood Stem Cells (PBSC) are at a certain level in the blood stream, the donor is attached to a blood cell separator (apheresis machine) where the cells are withdrawn from the blood of the donor.
In the week leading up to your transplant, you are given a few days of very high doses of chemotherapy, and sometimes radiotherapy, to destroy your underlying disease, and suppress your immune system so that it will accept the donor stem cells. This is called conditioning therapy. After you have finished this part of your treatment, the donated stem cells are infused through a vein into your blood stream. This is similar to a blood transfusion. From here the stem cells make their way to your bone marrow where they become established and start making new blood cells.
Your blood counts drop dramatically in the week following conditioning therapy. During this time you will be more at risk of infections (due to the lack of infection-fighting white blood cells) and bleeding (due to a lack of platelets).
Antibiotics and other drugs are commonly prescribed to help prevent or treat infections during this time, and you are likely to need platelet transfusions to reduce the risk of bleeding. Red blood cell transfusions are given when haemoglobin levels are too low. During this time you are likely to be experiencing some of the common side effects of chemotherapy, and radiotherapy including nausea and vomiting, mucositis (sore mouth) and bowel problems (diarrhoea)
Most of the side effects of an allogeneic transplant are caused by the conditioning therapy used. While many of these side-effects last for a short time, some can last longer. Some side-effects persist for months and occasionally years after the transplant.
The donor’s stem cells can cause a common, sometimes serious complication of allogeneic transplants called graft-versus-host-disease (GVHD). This is an immune reaction whereby cells from the donor’s immune system recognize the patient’s body as foreign and attack it. GVHD can vary in severity and the extent to which it causes problems in the body.
When it develops soon after the transplant it is called acute GVHD. This is usually managed with drugs, including steroids to further suppress the new immune system and reduce the symptoms. It can also develop at a later stage, or persist for months and sometimes years after the transplant. If you are having an allogeneic transplant you will be given special drugs called immune-suppressants (anti-rejection drugs) before, during and for some time after the transplant. They also help to suppress the ‘new’ (donor’s) immune system to reduce GVHD and prevent it from causing serious problems in the body. These drugs also help to reduce the risk of the donor’s stem cells being rejected by your body.
It can take a year or even longer for the immune system to fully recover following an allogeneic transplant. As such there is a risk of infection for some time after your transplant. It is important to take some sensible precautions to prevent infections during this time (for example, avoid contact with people with an illness like flu or chicken pox).
High dose treatment can cause fertility problems, affecting your ability to have a baby in the future. In women these treatments can also cause an earlier than expected onset of menopause (change of life), even at a young age.
Your doctor will discuss with you all the expected side-effects of your treatment, and the steps that can be taken to help reduce or prevent them.