Allogeneic stem cell transplantation

More than 90% of the patients who need an allogeneic stem cell transplant will have a donor that fulfils the criteria for donating a stem cell transplant. The optimal donor is a sibling of the patient with an appropriate tissue type (HLA-identical match). It is also possible to have a child, either of the parents of the patient as stem cell donors or donor can also be from extended family members such as aunts, uncles or even cousins; such a donor is called a haploidentical donor.

Since not all who need an allogeneic stem cell transplant have a matching donor in the family, most patients will have a matching donor in the domestic Red Cross registry of stem cell donors and in international donor registries. Once a suitable donor has been identified, the donor and the patient will undergo the necessary preparatory steps before the actual procedure. Today, the donors of allogeneic stem cell transplants undergo collection of stem cells from the circulating blood more often than from the bone marrow.

The timing of the allogeneic stem cell transplantation is always managed so that it is optimal from the point of view of the phase of the patient’s disease. The time the patient spends in the hospital is usually 4–6 weeks; of these, the conditioning regimen requires 1–2 weeks. The conditioning regimen depends on the disease being treated, the patient’s age and concomitant illnesses and on previous treatments. The conditioning regimen includes chemotherapy and, possibly, radiation treatment to reduce the tumour burden. The conditioning regiment will also stun the patient’s immune system for a time. This guarantees the undisturbed function of the transplanted cells and the production of new, healthy blood cells. During the conditioning regimen the patient may experience nausea and mucous membrane problems. After completion of the conditioning regimen, the collected stem cells are infused (transplanted) to the patient in a procedure that is like a blood transfusion.

A central problem for patients who have received an allogeneic stem cell transplant is the risk of infections. This risk prevails as long as the blood count is low. An allogeneic stem cell transplantation is an advanced and demanding medical procedure associated also with other risks. The most common treatment-related complications are severe graft-versus-host rejection reactions and posttransplant virus infections. Also, the blood disease may recur. The patient needs meticulous follow-up within the open care and often follow-up of a very long duration. Most problems post transplantation emerge only after the transplantation period in the hospital is over. New treatments and cell therapies are constantly being developed to prevent and combat the complications of allogeneic stem cell transplantation.