Stem cell transplantation is used to treat lymphoma patients when standard treatment has failed. Currently, this type of therapy is used only rarely in patients with skin lymphoma, although the procedure may be used more commonly in the future.
SCT allows doctors to use very high doses of chemotherapy to try to wipe out the lymphoma. Such high doses would normally permanently damage the normal cells in the bone marrow, which would halt the production of blood cells. This could be life threatening.
Stem cells (that form the blood cells) are the earliest form of bone marrow cells. Once they are produced in the bone marrow, they develop into normal blood cells such as red blood cells, white blood cells, and platelets. Stem cells can be collected from the blood of a donor or the patient prior to the use of high-dose chemotherapy. They are then given back to the patients after they have had the very high-dose chemotherapy. The stem cells can repopulate the bone marrow, allowing normal blood cell production to begin once again. This treatment can be used for some patients who are in remission or if they have a relapse during or after treatment.
Blood-forming stem cells can be taken either directly from the bone marrow or removed from the blood. When bone marrow stem cells are used, it is called a bone marrow transplant, or BMT. If the stem cells used have been removed from the blood, it is called a peripheral blood stem cell transplant, or PBCST. Using cells from the peripheral blood is much more common. Regardless of where the stem cells are taken from (blood or bone marrow), there are 2 main kinds of SCT -- allogeneic and autologous.
Allogeneic stem cell transplant
In an allogeneic stem cell transplant, the blood-forming stem cells come from a donor. The ideal donor is a relative (often a brother or sister) whose tissue type (HLA type) is matched to the patient. This lowers the chance of a certain serious side effect called graft vs. host disease (discussed later in this section). If the donor is someone who is a match to the patient but is not related, the transplant carries more risks. Allogeneic transplantation has limited usefulness, however, because of the need for a matched donor. Another drawback is that side effects of this treatment are too severe for most people over 55 years old. About one fourth of all transplants for lymphoma are this kind.
Non-myeloablative transplants: This is a special kind of allogeneic transplant that relies on the donor cells' immune response to kill the lymphoma cells. Most transplants use chemo to kill the cancer cells. In a non-myeloablative allogeneic transplant (also called a mini-allo), lower doses of chemo are given to prepare the patient for transplant. Then stem cells from a matched donor are given. The chemo is not enough to kill all the lymphoma cells but is enough to let the donor cells take hold in the marrow. Over time the donor cells take over the bone marrow and can then develop an immune response against the lymphoma cells, destroying them. This is called a graft vs. lymphoma effect.
The problem with these transplants is the high risk of graft-versus-host disease (discussed later in this section). Researchers are looking for ways to eliminate the graft-versus-host response while keeping the graft-versus-lymphoma effect. Because lower chemo doses are used, this type of transplant can be used to treat patients who would be considered too old for a regular allogeneic transplant.
Autologous stem cell transplant
An autologous stem cell transplant uses the patient's own blood-forming stem cells instead of cells from a donor. These stem cells are removed from the patient's bone marrow or bloodstream and stored before the transplant. Then, high doses of chemotherapy are given and the patient gets their own cells back. This type of transplant may not be a good option if the lymphoma has already spread to the bone marrow or blood. It is not often possible to get stem cells free of lymphoma cells. Even after purging (treating the stem cells in the lab to kill or remove lymphoma cells), returning some lymphoma cells with the stem cell transplantation is possible.
In either case, blood-forming stem cells collected from the donor or the patient are carefully frozen and stored. The patient then receives high-dose chemotherapy and sometimes whole body radiation treatment as well. This destroys remaining cancer cells, but it also kills all or most normal cells in the bone marrow. After therapy, the frozen stem cells are thawed and returned to the body, by infusing these stem cells directly into a vein, just like a blood transfusion.
Bone marrow or peripheral blood stem cell transplant is a complex treatment. If doctors think the patient may benefit from transplantation, the best place to have it done is at a nationally recognized cancer center where the staff has experience with the procedure and with managing the recovery period. Patients should not hesitate to ask the doctor about the number of times he or she has done this procedure, the number done at their facility, and their results with cases such as theirs. Experienced, knowledgeable support staff are key factors in providing the best care.
Side effects of transplant
Side effects from a stem cell transplant are generally divided into early and long-term effects. The early complications and side effects are basically the same as those caused by any other type of high-dose chemotherapy. They are caused by damage to the bone marrow and other rapidly growing tissues of the body and include:
- hair loss
- mouth sores
- loss of appetite
- nausea and vomiting
- low blood counts
Complications and side effects that can persist for a long time or that may occur many years after the transplant include:
- radiation damage to the lungs, causing shortness of breath
- graft-versus-host disease, which occurs only in allogeneic (donor) transplants (see below)
- damage to the ovaries in women, that can cause infertility and premature menopausal symptoms
- infertility in male patients
- damage to the thyroid gland that can cause problems with metabolism
- cataracts (damage to the lens of the eye that can affect vision)
- bone damage called aseptic necrosis. If damage is severe, the patient will need to have part of the affected bone and the joint replaced.
- development of leukemia years later
Graft-versus-host disease (GVHD): This is the major complication of allogeneic (donor) stem cell transplants. It occurs because the donor cells establish a new immune system in the patient. The new immune system then may "see" the patient's tissues as foreign and react against them. Some difficult symptoms are severe skin rashes with itching, severe diarrhea, and damage to the liver and lungs. The patient may also become easily fatigued and develop muscle aching. Sometimes the graft-versus-host disease becomes chronic and disabling and, if it is severe enough, can be fatal. Usually drugs can control graft-versus-host disease.
On the positive side, the graft-versus-host disease also leads to graft-versus-lymphoma activity. Lymphoma cells remaining after the chemotherapy and radiation therapy are often killed by immune reactions of the donor cells since the lymphoma cells are seen as foreign by the donor's immune system as well. For this reason, mild graft-versus-host disease can be a good thing.
For more information on the procedures, see our document, Bone Marrow and Peripheral Blood Stem Cell Transplants.
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