Types of Transplant

There are many terms that describe the transplant process: bone marrow transplant, stem cell transplant, peripheral blood transplant and umbilical cord blood transplant. These terms generally refer to the same type of transplant, using different sources of stem cells.

Patients requiring transplant have stem cells taken from one of these sources: bone marrow, peripheral blood or umbilical cord blood. The stem cells are primitive cells in the marrow that are important in making red blood cells, white blood cells and platelets. The stem cells are largely found in the marrow, but some leave the marrow and circulate in the peripheral blood.

The stem cells can be harvested or collected from the marrow, the peripheral blood or the cord blood of a newborn child. Regardless of the source from where the stem cells are collected, we refer to this process as a Blood and Marrow Transplant (BMT).

There are four types of transplants:

> Autologous Stem Cell Transplant
> Syngeneic Stem Cell Transplant
> Allogeneic Stem Cell Transplant
> Non-myeloablative Stem Cell Transplant

1. Autologous Stem Cell Transplant

In autologous transplant, the stem cells are collected from the patient and stored. An important component of transplant is that enough stem cells are collected to ensure engraftment. In some cases, peripheral blood stem cell collection and bone marrow harvest are necessary to obtain a satisfactory number of stem cells. This type of transplant can be used to treat many diseases such as multiple myeloma, non-Hodgkin’s lymphoma, Hodgkin’s disease, testicular cancer and occasionally leukemia.

After the stem cells are collected from you and stored, you are admitted to the hospital. High doses of chemotherapy are given through a central line directly into the venous (vein) system. The chemotherapy regimen will last over a period of days, depending on the specific treatment protocol.

This high dose therapy reduces the disease by attacking the cancer cells. As with all chemotherapy, health cells are also affected. It is common to have side effect such as nausea, vomiting, hair loss and mouth sores. Medications will be given to help control these symptoms.

The stem cells are reinfused through the central catheter and growth factors begin five days following the stem cell infusion, continuing daily until the white blood cell (WBC) count recovers.

The immune system will be affected by the chemotherapy, and there is a risk for developing serious infections. There is the need for antibiotics, blood and platelet transfusions and frequent blood test to monitor blood counts. Special precautions are followed in order to prevent infection and bleeding. Hospitalization is usually required for two to four weeks.

Following discharge from the hospital, there are frequent doctor visits, blood counts, blood and platelet transfusions and growth factor injections. Full recovery can take up to three to six months and in some cases longer.

2. Syngeneic Stem Cell Transplant

A syngeneic stem cell transplant is very similar to an autologous stem cell transplant. The biggest difference is that instead of collecting the stem cells from the patient, the patient’s identical twin will be the donor. A syngeneic transplant is similar to an autologous transplant because an identical twin’s genetic makeup in exactly the same, thereby greatly reducing the risk of graft-versus-host disease.

3. Allogeneic Stem Cell Transplant

An allogeneic stem cell transplant uses the stem cells collected from a donor. Allogeneic stem cell transplants are most frequently used to treat patients with leukemia, aplastic anemia and lymphomas, including Hodgkin’s disease and non-Hodgkin’s lymphoma. The types of diseases that are treated with allogeneic transplant are constantly expanding.

Allogeneic stem cell transplant differs from autologous transplant because the patient requires a donation of stem cells from a brother, sister or a person unrelated to the patient. These types of transplants can be referred to as a related allogeneic transplant or an unrelated allogeneic transplant. One source of allogeneic stem cells is the umbilical cord blood of a sibling or an unrelated donor.

Identifying a donor can take weeks or months. A well-matched donor is important to the success of the transplant and the time it takes to locate a match varies from patient to patient.

The patient and potential donors undergo a blood test, human leukocyte antigen or HLA testing, to determine if they have similar tissue types. HLA is a system used to identify the unique markers (antigens) recognized by the immune system. Antigens are the markers on a cell that give scientists the ability to differentiate each cell. These markers are found on most all cells including white blood cells (WBC).

The patient and donor’s WBCs are isolated from the blood sample and studied to determind which antigens are present. When determining a patient’s HLA type, there are eight antigens considered to be most important for matching. HLA typing is inherited through genes passed down from parents. Four of these antigens come from your mother and four come from your father.

Once a donor is identified and screened, the patient’s treatment is scheduled. The patient receives a central venous catheter upon admission. Before transplant, the patient will receive a high-dose chemotherapy regimen and in some cases total body irradiation. This can take up to a week depending on the treatment protocol.

The donor’s stem cells may be harvested before the patient starting high-dose chemotherapy, but frequently the donor’s bone marrow is harvested the day of infusion (transplant day 0).

Following completion of chemotherapy and/or radiation, there may or may not be a period of rest for one to two days. Then the donor stem cells or bone marrow is infused into the patient via the central venous catheter.

Over the next two weeks, the patient is at severe risk for developing infection and side effects related to chemotherapy. Antibiotics are given to try to prevent and treat infection. Blood and platelet transfusions are administered and frequent tests and monitoring will be done to try to prevent serious chemotherapy side effects. Medications will be given to help control nausea, diarrhea and pain. Pain is most commonly associated with mouth or throat sore (mucositis).

When the WBC counts start to recover, you are at risk for developing graft-versus-host disease. Graft-versus-host is a serious side effect caused when the donated stem cells (the graft) recognize specific cells and tissue in your body as foreign and launch an attack. Medications are given to prevent and treat graft-versus-host disease.

Patients receiving allogenic stem cell transplants are usually admitted to the hospital for three to four weeks. Following discharge from the hospital, daily outpatient visits are required for an extended period of time. Patients will be evaluated for graft-versus-host disease, infection and may require readmissions to the hospital for treatment of serious complications. Recovery is complex and varies from patient to patient.

4. Non-myeloablative Stem Cell Transplant

This is a type of allogeneic transplant similar to traditional allogeneic transplant. It gives patients who cannot tolerate rigorous pre-transplant chemotherapy because of age or poor overall health condition an option for allogeneic transplant.

Non-myeloablative transplant involves giving the patient less rigorous chemotherapy that does not completely destroy the existing bone marrow. The patient receives an infusion of related or unrelated donor bone marrow or stems cells to create a graft versus malignancy (GVM) effect, in which the patient’s new immune system destroys any cancer cells remaining in the patient.

The GVM phenomenon exists in traditional allogeneic transplant, where the new immune system kills few remaining cancer cells that have survived high-dose chemotherapy. After years of research, sufficient numbers of non-myeloablative transplants have been performed to conclude that it is a viable option for some patients who are otherwise not a candidate for full allogeneic transplant; however, not all risks and benefits have been clearly established. Patients experience less toxicity related to chemotherapy and the initial admission to the hospital is typically shorter.

The patient is expected to develop graft-versus-host disease and is at risk for severe complications. Readmissions to the hospital are common. The recovery from this type of transplant is similar to that of a full allogeneic transplant; it is complex and varies greatly from patient to patient.