Stem cells are cells found in the bone marrow and are collected from the donor or the patient before they receive high dose chemotherapy. The cells are then returned to help the marrow to become repopulated.
There are potentially serious side effects associated with these treatments. They are not suitable for everyone and are not done routinely. Doctors will consider the patient’s general health and fitness before recommending this course of treatment. This often means the risks of carrying out stem cell transplants in older people who have other health problems are too high to recommend this approach.
Stem cell transplants are only performed after chemotherapy has been given to reduce the burden of the disease, put it into future remission and to consolidate (build on) that remission. It is recommended that stem cell transplants are carried out after a maximum of two lines of previous treatment, as this is when the results are best.
Autologous stem cell transplant (ASCT)
Patients undergoing ASCT have some of their own stem cells collected and stored in advance of receiving a course of high-dose chemotherapy to kill any remaining lymphoma cells. A combination known as LEAM is often used (this stands for Lomustine, Etoposide, Ara-C and Melphalan), administered over a five day period intravenously.
Once returned to the body (dripped in to the vein like a blood transfusion), the stem cells make their way to the bone marrow, where they form new blood cells to restore the bone marrow to normal function. This takes seven to ten days. While the stem cells are making their way to the bone marrow and becoming re-established, the patient is particularly vulnerable to infection and requires a period of inpatient treatment and monitoring.
This form of stem cell transplant is not curative, but it can lead to a long-lasting remission; in other words, the disease can stay at a very low level for quite a long time (typically a number of years) before further treatment is needed.
Allogeneic stem cell transplant (allo-SCT)
In this kind of transplant the stem cells come from another person. The donor might be a close relative, such as a brother or sister, or may be someone unrelated who has a matching tissue type. After the patient receives high dose chemotherapy, the donor’s stem cells are infused into the bloodstream via a cannula and within two or three weeks, produce donor blood cells in the patient’s bone marrow. These new cells resupply the patient with blood cells which can also directly fight against any leftover lymphoma cells. In this kind of stem cell transplant, the donor’s immune system is used as the weapon within the patient.
There is an ongoing risk that the donor immune system may react against the patient’s healthy tissues, causing a variety of complications after the transplant. Special treatment is needed to suppress the patient’s immune system for a period of time to allow it to accept the donor’s cells (even though they are a tissue match), and this inevitably leads to the risk of unusual and dangerous infections. As with ASCT, a period of hospitalisation is required.
While this form of transplant can offer the possibility of cure for some people with WM, it is a more hazardous procedure than an autologous transplant and the patient’s general health needs to be good before being considered for it. Currently, it is only considered if a range of other treatments have failed.