In a stem cell transplant, stem cells are transferred to the patient to replace the damaged blood cells in the bone marrow and rebuild the immune system. Depending on the type of donor, doctors differentiate between autologous stem cell transplantation (treatment with the patient’s own blood stem cells) and allogeneic stem cell transplantation (treatment with foreign blood stem cells).
What is a stem cell transplant?
A stem cell transplant is the transfer of blood stem cells from a donor to a recipient. Experts also refer to this as “hematopoietic blood stem cell transplantation” (HSCT). “Hematopoietic” means “blood-forming”.
For the transplant, doctors take blood stem cells from the (peripheral) blood flowing in the veins or from the bone marrow. They then prepare it for the therapy.
The stem cells required can come from the patient themselves(autologous stem cell transplantation). However, they can also be donated by a suitable related or unrelated person(allogeneic stem cell transplantation).
The decision between autologous and allogeneic stem cell transplantation depends on the type of disease, the patient’s state of health and the availability of a suitable stem cell donor.
Autologous stem cell transplantation is used for various life-threatening diseases of the hematopoietic system. For example with:
An allogeneic stem cell transplant is an option for the following diseases, among others:
Definition: What are blood stem cells?
About half of human blood consists of a liquid component, the blood plasma, and the other half consists of blood cells. There are basically three main types of blood cells:
- Red blood cells (erythrocytes) transport oxygen and carbon dioxide.
- White blood cells (leukocytes) defend the body against pathogens.
- Blood platelets (thrombocytes) are important for blood clotting and wound healing.
Blood cells only live for a limited time and die after a few days or months, depending on the type. This is why our bone marrow has to produce billions of new blood cells every day, especially red blood cells. This task is performed by the blood stem cells, which are the “primordial cells” that produce all other blood cells.
Most stem cells are found in the bone marrow, a sponge-like tissue inside certain bones, such as the hip bone. A small proportion of the stem cells also circulate directly in the blood.
To ensure that there are always enough blood cells, the stem cells are constantly dividing. Each division produces two cells: a new stem cell and a precursor cell that develops into a red or white blood cell or a platelet. As soon as the blood cells are mature, they leave the bone marrow and enter the bloodstream.
What forms of stem cell transplantation are there?
There are two main types of stem cell transplantation, which differ according to the origin of the stem cells. Each type of stem cell transplant has its own areas of application and risks. The choice of the appropriate procedure depends on the disease.
Autologous stem cell transplantation
In autologous stem cell transplantation (autologous = from the same individual), the blood stem cells come from the patient themselves. The patient’s own blood stem cells are removed before high-dose chemotherapy, frozen and returned to the patient’s body via an infusion after treatment. These own, healthy stem cells are intended to renew the bone marrow and the immune system.
Allogeneic stem cell transplantation
In allogeneic stem cell transplantation (allogeneic = from genetically different individuals), the stem cells come from a healthy donor. The donor can be a suitable family member or a genetically suitable unrelated donor. On the one hand, allogeneic stem cell transplantation carries the risk that the new immune system will recognize the patient’s organs as foreign and attack them (graft-versus-host disease). There is also the possibility of a rejection reaction, as the recipient’s immune system identifies the foreign stem cells as “invaders”.
Special form: haploidentical stem cell transplantation
Haploidentical stem cell transplantation is a special form of allogeneic stem cell transplantation in which the genetic match between donor and recipient is 50%. A haploidentical donor is often a parent, a sibling or a child of the patient. This form is used if a completely suitable dispenser cannot be found. However, special medical measures have now greatly reduced the risk of a rejection reaction.
Procedure for a stem cell transplant for cancer
During a stem cell transplant, the treating physicians transfer the patient’s own or foreign blood stem cells into the bloodstream. The transplantation of healthy blood stem cells enables the bone marrow to produce new, healthy blood cells and strengthen the immune system.
Although the term “transplant” is reminiscent of an operation, the procedure is more like a blood transfusion. The healthy blood stem cells are infused into the patient’s vein. From there, the cells migrate independently into the bone marrow.
The stem cell transplant procedure step by step:
- Preparatory treatment (conditioning)
Before the actual transplant, the patient receives so-called conditioning treatment – usually chemotherapy and/or radiation. This treatment destroys the diseased or defective blood cells and suppresses the immune system to make room for the new stem cells. This reduces the risk of the body rejecting the new cells again.
- Transplantation of blood stem cells
The healthy stem cells flow into the patient’s blood via an infusion – similar to a blood transfusion. The stem cells then migrate via the bloodstream to the bone marrow, where they begin to multiply and form new blood cells.
- Growth and formation of new blood cells
In the bone marrow, the stem cells begin to transform into red and white blood cells and platelets. They are important for oxygen transport, immune defense and blood clotting. During this time, the patient’s immune system is still weakened. There is an increased risk of infections and other complications.
- Aftercare and monitoring
Intensive follow-up care is required after a stem cell transplant. The attending physicians monitor the blood values and general state of health to ensure that the new stem cells grow well and no rejection reactions occur. In order to avoid life-threatening rejection reactions, patients who have undergone an allogeneic stem cell transplant are usually given special medication to suppress the immune system (immunosuppressants) and medication to prevent infections for around six months. During this time, those affected should avoid crowds and public transportation as much as possible.
What complications and side effects can occur?
As with any medical procedure, complications can also occur during a stem cell transplant. The most common risks include
- Rejection reactions: The body recognizes the foreign stem cells as invaders and attacks them.
- Infections: As the immune system is weakened, there is an increased risk of infection.
- Organ damage: Conditioning treatment can have side effects that also affect other organs such as the liver or heart.
- Graft-versus-host disease (GvHD): A severe form of “reverse” rejection reaction in which the new, transplanted immune system attacks the recipient’s organs.
Stem cell transplantation: What happens during aftercare?
Long-term medical care is required after a blood stem cell transplant. In the first few weeks and months, the doctor monitors the patient’s state of health closely. Regular blood tests and check-ups ensure that complications can be detected and treated at an early stage. Regularly adjusting the dose of medication supports the immune system and reduces the risk of infection.
Who covers the costs of a stem cell transplant?
As a rule, health insurance companies in Switzerland cover the costs of a medically necessary stem cell transplant. A cost approval from the health insurance company can ensure that financing is arranged.
Prognosis: What are the chances of success after a stem cell transplant?
The prognosis after a stem cell transplant depends on several factors, including the underlying disease, the patient’s state of health, age, the availability of suitable donor cells and the ability of the donor cells to form new, healthy blood cells.
Experts for stem cell transplantation
There are several specialized clinics and transplant centers in Switzerland that carry out stem cell transplants in children and adults. The University Hospital Zurich is one of the leading institutions.
At the University Hospital Zurich (USZ), you will receive comprehensive care from our experienced interdisciplinary team throughout the entire treatment process. In addition to medical care, you will receive support from various areas such as nutritional counseling, social counseling, physiotherapy, psycho-oncology and other specialties.
The USZ is a center for stem and immune cell therapy recognized by the European Society for Blood and Marrow Transplantation (EBMT) and has JACIE accreditation.
