Stem Cell Transplantation
For patients with lymphoma, myeloma or leukaemia, stem cell transplantation is often used as part of the treatment. These procedures are generally reserved for patients under the age of 65, but older people who are particularly healthy may also be suitable.
Adult stem cells are found in many sites around the body, including the brain, bone marrow, blood, skeletal muscles, skin and liver, to name a few. They are capable of dividing or self-renewing indefinitely, although they remain in a non-dividing state for years until activated by disease or injury. Once activated, stem cells are vital for the repair and regeneration of damaged or ageing body tissues, such as the bone marrow.
Initially, stem cell transplants were developed to allow high doses of chemotherapy to be given. When the dose of chemotherapy needed to eradicate the leukaemia or lymphoma is very high, the bone marrow may be permanently destroyed. Without healthy bone marrow, the patient will die from bone marrow failure. Stem cell transplantation reintroduces the necessary cells to repair the damage from the chemotherapy by one of two methods: preserving the patient's own bone marrow out of the body whilst the chemotherapy is given (autologous stem cell transplantation), or transplanting new bone marrow into the patient from a normal donor (allogeneic bone marrow transplantation).
Autologous stem cell transplantation
The commonest form of stem cell transplantation is autologous stem cell transplantation. This involves collection and storage of your own bone marrow stem cells. The stem cells are collected from the blood stream after they have been triggered to leave the bone marrow and circulate in the blood for several days. Either soon after the collection or several years later, the stem cell transplant is undertaken, reintroducing the removed cells back into the bone marrow. This usually involves 2-3 weeks in hospital during which time high doses of chemotherapy are administered, and then the stored stem cells are infused back into the body. The duration of chemotherapy varies from 1 day to 6 days, depending on the particular diagnosis; however, most of the time in the hospital is spent recovering from the after effects of chemotherapy and waiting for the stem cells to find their place in the bone marrow and regrow. The stem cells are like seeds, once they have been returned to your blood stream they find a suitable space to grow in the bone marrow and over a period of about 10 days start to make new blood cells.
Allogeneic stem cell transplantation
An alternative to using stems cells from the patient is the use of stem cells from a brother, sister or an unrelated volunteer donor.
Advantages of allogeneic stem cell transplantation:
- Components of the donor's immune system, transplanted along with the stem cells, is often able to eradicate the disease being treated. A major reason for the success of treatment with allogeneic stem cells is not the high doses of chemotherapy that have been administered, but rather the effect of the donor's immune system attacking the leukaemia or lymphoma.
- Some patients can not produce enough stem cells to safely undergo stem cell harvesting and then transplantation with their own stem cells.
- In some cases stem cells can not be collected without collecting the abnormal leukaemia or lymphoma cells, which may then be returned to the patient when the stem cells are returned.
Disadvantages or problems with allogeneic bone marrow transplantation:
- Many patients do not have a suitable compatible donor.
- The side effects of an allogeneic transplantation, caused by measures to prevent rejection of the donated cells or by the donated cells attacking the host, are substantial and may be permanent or fatal.
- There are also advantages of an autologous transplant over an allogeneic stem cell transplant
For more information on stem cell transplantation please follow the links below.
'Stem Cell Transplants' provided by the Leukaemia Foundation
'Patient information: Bone marrow transplantation' provided by UpToDate