As noted earlier, chemo can harm normal cells as well as cancer cells. A stem cell transplant (SCT) offers a way for doctors to use the very high doses of chemo needed for effective treatment. Although the drugs destroy the patient's bone marrow, transplanted stem cells can restore the blood-producing bone marrow stem cells.
Stem cells for transplantation are collected from the bone marrow or from the bloodstream (in a process called apheresis). Bone marrow transplant was more common in the past. Now it has been largely replaced by cells taken from the bloodstream.
These blood-forming stem cells can come from either the patient or from a donor whose tissue type closely matches that of the patient. The donor may be a brother or sister or, less often, a person not related to the patient.
It's not yet clear how helpful stem cell transplants are in patients with chronic lymphocytic leukemia (CLL). When these treatments are used, it is most often in clinical trials looking to test how well they work.
The transplant process
First, blood-forming stem cells are collected from either the patient or a matched donor. The cells are frozen and stored. Patients are then given very high doses of chemo to kill the cancer cells. They may also get total body radiation to kill any remaining cancer cells. After treatment, the stored stem cells are given to the patient as a blood transfusion. Then the waiting period begins as the stem cells settle in the patient's bone marrow and start to grow and produce blood cells.
People who receive a donor's stem cells are given drugs to prevent rejection as well as other medicines as needed to prevent infections. Usually within a couple of weeks after the stem cells are infused they begin making new white blood cells. Then they begin making platelets, and finally, red blood cells.
Patients having SCT have to be kept away from germs (in protective isolation) as much as possible until their white blood cell count is at a safe level. They may be kept in the hospital until the white cell count reaches a certain number, usually around 1,000. Even after they go home, they will be seen in the outpatient clinic almost every day for many months.
"Mini-transplants"
Many patients over the age of 55 can't have a regular transplant that uses high doses of chemo. Some may be able to have what is called a "mini-transplant" (non-myeloablative transplant or reduced-intensity transplant), where they get lower doses of chemo and radiation that do not destroy the all cells in their bone marrow. They then get the donor stem cells. These cells enter the body and form a new immune system, which sees the leukemia cells as foreign and attacks them (a "graft-versus-leukemia" effect). Many doctors still consider this an experimental treatment in the treatment of CLL, and clinical trials are being done to find out how useful it may.
To learn more about stem cell transplants, please see the American Cancer Society document, Bone Marrow and Peripheral Blood Stem Cell Transplant.
Some things to keep in mind
Stem cell transplantation is a complex treatment. If the doctors think that a person with leukemia might be helped by this treatment, it is important that it be done at a hospital where the staff is experienced with the procedure. Some transplant programs may not have experience in certain transplants, especially those from unrelated donors.
Stem cell transplantation costs a lot -- more than $100,000. It often requires a long hospital stay. Because some insurance companies see it as an experimental treatment, they might not pay for it. You should find out what your insurer will cover and what you might have to pay before choosing to have a transplant.
Side effects of SCT
Side effects from a stem cell transplant can be divided into early and long-term effects.
Early side effects: Early side effects are basically the same as those of any other type of high-dose chemo (low blood cell counts, nausea, vomiting, hair loss, etc.). They are caused by damage to the bone marrow and other fast growing tissues of the body.
Long-term side effects: Some side effects can go on for a long time. And sometimes they don't show up until years after the transplant. Long-term side effects could include the following:
- Graft-versus-host disease (see below)
- Radiation damage to the lungs, causing shortness of breath
- Damage to the ovaries causing infertility and loss of menstrual periods
- Damage to the thyroid gland that causes problems with the way the body uses food for energy (metabolism)
- Damage to the lens of the eye (cataracts)
- Bone damage; if damage is severe, the patient may need to have part of the bone and joint replaced
Graft-versus-host disease is the main problem of a donor stem cell transplant. It happens when the immune system of the patient is taken over by that of the donor. The donor immune system then begins reacting against the patient's other tissues and organs.
Symptoms can include severe skin rashes with itching and severe diarrhea. The liver and lungs may also be damaged. The patient may also become tired and have aching muscles. If bad enough, the disease can be fatal. Drugs that weaken the immune system are often given to try to keep GVHD under control.
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