Stem Cell Transplantation

A stem cell transplantation (SCT) is a procedure in which a patient receives healthy stem cells to replace damaged stem cells. This procedure can cure certain blood diseases, or increase the chance for a durable remission. Stem cells are a special kind of cells that can multiply and transform into many different cell types. Hematopoietic stem cells are stem cells in the bone marrow that can give rise to different blood cells. Once these blood cells are mature, they leave the bone marrow and enter the bloodstream to fulfill their function.

In most stem cell transplantations, peripheral stem cells are used. This means that hematopoietic stem cells are stimulated by growth factors and pushed into the blood stream, after which they can be harvested, by a procedure called apheresis. In special cases, stem cells can also be obtained directly from the bone marrow of a donor by punctures in the iliac crest, under full anesthesia.

There are two types of stem cell transplantation: autologous, using the patient’s own stem cells, and allogeneic, using stem cells from a donor.

In an allogeneic SCT, stem cells from a donor are used to rebuild the bone marrow after chemotherapy, and to also install a new immune system to form a permanent gatekeeper against the malignant cells (graft versus leukemia effect). As a result, an allogeneic SCT gives a stronger protection against a disease relapse compared to an autologous SCT. At the same time, however, as the stem cells come from a donor, rejection can be a troublesome side effect. In this case, the donor cells attack the host’s body (graft versus host disease). In this light, conditioning therapy prior to an allogeneic SCT aims at destroying not only the patient’s bone marrow, but also reduce the chance for a graft rejection.

An allogeneic stem cell transplantation is a heavy treatment. Therefore, an age limit is often used, and the general condition of the patient plays an important role. For older patients, a lower dose conditioning chemotherapy is used, which does not completely destroy the bone marrow. After transplantation, the donor stem cells, and the patient’s own stem cells co-exist. Over the course of a few months, the donor stem cells will gradually take over the bone marrow and help to kill the remaining diseased stem cells.

Before an allogeneic SCT can be performed, a suitable donor has to be found, with a sufficient similarity to the patient’s tissue type. Medication will be administered to prevent (reverse) rejection after an allogeneic SCT. When looking for a donor, siblings are considered first. If there is no suitable sibling, an unrelated donor can be sought in national and international donor banks. These banks consist of anonymous volunteers from all over the world, who are willing to donate stem cells. Half-compatible siblings, parents or children can also be considered as a donor in a so-called haplo-identical stem cell transplantation.

The donor will receive growth factors to stimulate the hematopoietic stem cells in the bone marrow and push them into the blood stream where they can be harvested via a procedure called apheresis. Fresh donor stem cells are then transported and administered to the patient via an intravenous catheter. In special cases, stem cells can be obtained directly from the bone marrow by punctures in the iliac crest, under full anesthesia.

Prior to a SCT, the patient is admitted to the hospital to receive conditioning therapy. In most cases, this consists of chemotherapy, although radiotherapy may also be used in case of an allogeneic SCT. Following this conditioning therapy, the number of blood cells begins to decline. As a result, blood and platelet transfusions are often required, and the patient becomes very susceptible to infections. Therefore, patients are staying in a germ-free isolation room. In addition, preventive antimicrobial agents are administered and infections are treated promptly. After a patient has received their own thawed peripheral stem cells, it takes an average of 8-10 days for the stem cells to begin rebuilding the blood. In the case of an allogeneic SCT, fresh donor cells are transfused and start to rebuild the blood cells after an average of 10- 14 days.

Side effects of a SCT include a decreased appetite, nausea, vomiting, diarrhea, mouth pain (stomatitis or mucositis), (prolonged) fatigue and hair loss. Nutrition can be temporarily administered intravenously (TPN). Because chemotherapy, nutrition and antibiotics must all be given together, a central catheter with 3 access routes is often placed in a large blood vessel under the collarbone. To promote their recovery, patients are advised to exercise as much as possible.

Most patients can leave the hospital after about 3-4 weeks in case of an autologous SCT and after 4-6 weeks if they received an allogeneic SCT. During the first months following the transplantation, patients need to come to the hospital on a regular basis for control visits and to work on their recovery. In the first months, patients experience fatigue, loss of taste and appetite and an increased susceptibility to infections. Six months after an allogeneic SCT, the childhood vaccinations are re-administered.

On the long term, a SCT may increase the risk for a secondary cancer. Patients are therefore advised to avoid excessive sun exposure and to stop smoking. In addition, regular breast exams are recommended for women. Infertility and an early onset of the menopause are common following a SCT. Men with a desire to have children can have their sperm frozen before the treatment. Fertility prevention in women can be planned in close collaboration with a fertility center. A team of doctors, nurses, psychologists, dieticians, physiotherapists and social workers offer assistance during and after the procedure to help patients cope with all the aspects of this heavy but often curative treatment.