Allogeneic Stem Cell Transplantation - Information & Specialists

Medical professionals associate two main goals with allogeneic stem cell transplantation:

1. First, it allows healthy blood-forming cells to be transplanted into a person with blood cancer (leukemia). These cells replace the damaged or dead bone marrow following aggressive chemotherapy or radiation therapy.
2. Second, the newly formed immune cells attack any remaining tumor cells in the patient.

In the context of allogeneic stem cell transplantation, doctors also refer to the graft-versus-leukemia (GVL) reaction.

Leukemia means “white blood” and refers to a variety of blood cancers that originate in the white blood cells (leukocytes) @ kalsoom /AdobeStock

For leukemia patients or people with rare brain tumors, doctors destroy cancer cells using chemotherapy or radiation therapy.

However, both the leukemia and the intensive treatment destroy the bone marrow. As a result, patients are no longer able to produce their own blood or maintain an immune system.

That is why the patient needs a stem cell transplant following cancer treatment. The new stem cells form new bone marrow and new blood cells.

Specialists refer to an autologous stem cell transplant when:

• The blood stem cells come from the patient themselves
• Doctors collect them before chemotherapy, purify them, and then reinfuse them

In this procedure, the donor and recipient are therefore one and the same person.

Allogeneic stem cell transplantation, on the other hand, refers to a situation where:

• The cancer patient (recipient) receives stem cells from another person (donor)

In most cases, the donor is a family member. However, unrelated individuals may also serve as donors.

Human bone marrow is the body’s most important blood-forming organ @ 7activestudio /AdobeStock

Since the donor and recipient are different individuals, the donor must have similar surface markers on their immune cells.

 These human leukocyte antigens (HLA) are present on all cells in the body. They signal to the immune system that everything is “at home” and in order.

Ultimately, this is also one of the reasons why our immune system does not turn against our own body. Foreign surface markers, on the other hand, are recognized as foreign, so our immune system usually attacks them.

In allogeneic stem cell transplantation, doctors transfer a “foreign” hematopoietic system into a recipient. The immune system that subsequently develops corresponds to that of the donor. It would therefore classify the recipient’s cells as foreign and attack them (graft-versus-host reaction).

To prevent this from happening, however, doctors must find a suitable donor before performing an allogeneic stem cell transplant. This is done based on the HLA pattern.

The goal is for the bone marrow to use the donor cells to produce blood and immune cells that are similar to those of the recipient. This significantly reduces the risk of a rejection reaction.

If an HLA-compatible donor is available (e.g., a relative), the donor’s blood or bone marrow stem cells can be harvested.

Doctors then prepare the recipient (usually a leukemia patient) for the transplant using high-dose chemotherapy or radiation therapy. 

The chemotherapy or radiation therapy destroys the body’s own bone marrow along with the cancer cells. As a result, after treatment, the patient has no ability to produce blood on their own and no immune system.

The recipient then receives the donor cells via a blood transfusion. The allogeneic stem cells migrate into the bone marrow cavities and form new bone marrow there.

After about three weeks, the new bone marrow has developed from the stem cells, and the recipient’s blood counts return to normal.

As blood production resumes, a new immune system develops. Once no tumor cells can be detected, the patient is cured.

About six months after the stem cell transplant, the patient has the same blood type as the stem cell donor @ Elnur /AdobeStock

For most patients, an allogeneic stem cell transplant is the only chance to regain their health. However, this treatment method is not entirely risk-free.

This is because there is a risk that the “donor bone marrow” will not engraft.

The much greater risk with an allogeneic stem cell transplant is that the newly formed immune system will attack the recipient’s body. Doctors refer to this as graft-versus-host disease. To prevent this, achieving the highest possible HLA match beforehand is particularly important. 

After the stem cell transplant, medications can suppress the immune response. However, this increases the risk of infection.

High-dose chemotherapy and total-body radiation therapy damage the germ cells in both men and women. As a result, the treatment can cause infertility.

You should therefore talk to your doctor about the possibility of cryopreservation (“freezing”) sperm and/or eggs before treatment. This may allow you to fulfill a desire to have children later in life, even if you are young now.

Another long-term effect can be secondary tumors caused by high-dose chemotherapy or radiation therapy. Nevertheless, allogeneic stem cell transplantation is often the only option for many patients.

Most patients who are candidates for an allogeneic stem cell transplant suffer from malignant blood disorders (leukemias). Leukemias should be treated by specialists in the fields of hematology and oncology. These fields are part of internal medicine.

You should be sure to seek advice from specialized cancer centers. These include, for example, centers for hemato-oncology or stem cell transplant centers. Today, these can be found at numerous university hospitals throughout Germany. You can find an overview of experienced specialists in allogeneic stem cell transplants as well as specialized cancer centers above.