When is a stem cell transplant indicated?

Author:  Dr. med. Gesche Riabowol née Tallen, Dr. med. Jörn Kühl, Editor:  Maria Yiallouros, Reviewer:  PD Dr. med. S. Voigt, English Translation:  Dr. med. Gesche Riabowol (nee Tallen), Last modification: 2024/05/04 https://kinderkrebsinfo.de/doi/e4965

There are two different reasons (indications) to perform a blood stem cell transplant (= haematopoietic stem cell transplantation‎, HSCT, SCT): on the one hand, you can replace diseased or malfunctioning bone marrow with healthy one, i.e. perform an organ transplant in the true sense of the word. On the other hand, bone marrow that has been destroyed as a result of treatment such as chemotherapy or radiotherapy can be replaced.

Since a blood stem cell transplant is still associated with considerable risks and long-term effects despite the great progress that has been made in recent years, the treating physicians and the transplant team will only opt for this treatment option under very specific conditions:

• In the case of cancer, a stem cell transplant is usually performed only if the probability of dying from the disease is greater than the risks of a transplant.
• In the case of non-fatal diseases (e.g. non-malignant congenital or acquired blood diseases), a stem cell transplant may be considered if, without this treatment, the disease leads to increasingly severe suffering with life-threatening consequences.

A stem cell transplant is a difficult path for the children and their relatives. However, therapy can be a chance to be cured of the life-threatening disease, thereby providing a chance to start a new life without disease.

Treatment of the underlying disease

Blood stem cells are often "sick". This means that one or more blood cell lines are not formed correctly or that the bone marrow‎ is so strongly interspersed with malignant cells that it is no longer possible to distinguish between "healthy" and "diseased" blood stem cells‎ or their derivatives.

In such cases, stem cells from another, healthy person (related or unrelated donor) must be transplanted (so-called allogeneic stem cell transplantation‎). Blood stem cell transplantation serves to treat the underlying disease, because the donor‘s blood stem cells are intended to replace one's own "diseased" or missing ones. This can be compared to an organ transplant such as a kidney or liver transplant.

A disease of the blood stem cells or the haematopoietic system in the bone marrow, as described here, is present, for example, in acute leukaemia‎s and certain Non-Hodgkin lymphoma‎s, but also in many – congenital and acquired – non-malignant blood diseases (such as sickle cell disease‎, beta-thalassaemia‎ or severe aplastic anaemia‎, SAA) as well as disorders of the immune or coagulation system.

Replacement of destroyed bone marrow

In children and adolescents with certain types of cancer (that do not affect the bone marrow), the success of treatment often requires substantial intensification of chemotherapy‎ (also referred to as high-dose chemotherapy‎) and, in some cases, total body irradiation [see radiation‎]. However, these intense treatments also lead to the destruction of the patient’s haematopoietic system in the bone marrow, so that vital blood cells can no longer be formed. Hence, haematopoietic stem cell transplantation is also indicated in these cases.

Since, however, the patient's bone marrow is healthy, his/her own stem cells can be used. For this purpose, blood stem cells‎ are collected from the patient prior to the start of high-dose therapy, stored in between and returned to him/her after completion of this treatment (so-called autologous stem cell transplantation‎). This is not a transplant in the true sense of the word, but a reinjection of one's own cells.

In this case, stem cell transplantation is not the therapy for the underlying disease, but rather a procedure to replace bone marrow and thus enable a more intensive approach with chemotherapy and/or radiotherapy.

The autologous stem cell transplantation described here is used, for example, in patients with high-risk Hodgkin lymphoma‎ or certain solid tumour‎s, which did not respond sufficiently to standard conventional therapies.

Indications

Before a haematopoietic stem cell transplant (HSCT) is performed, the treatment team assesses throroughly, whether it is indicated at all and also, which form of stem cell transplantation is most feasible for the patient (autologous‎ versus allogeneic‎, only HLA‎-identical versus not HLA-identical).

Advances in both conventional treatment options and transplant medicine will continue to influence these important issues. Since a stem cell transplant is very complex and can also be associated with complications, decision-making is based on whether the benefits of HSCT outweigh the downsides and whether its probability of survival is higher than after conventional therapy.

In order to continuously improve this decision-making process, the task forces designing the standardised treatment protocols constantly evaluate the results of the current and previous therapy studies and compare the outcomes after HSCT with those of other treatment strategies. The results of these analyses are used to optimise current treatment protocols.

Guidelines of the therapy plan

Recommendations on whether HSCT is an option for treatment of a certain disease or during a certain stage of disease are included in the therapy plan (therapy protocol) according to which your child will be treated.

Whether HSCT is actually performed depends on various factors, including the availability of a suitable donor and the patient's general condition. The treating physicians will take these and other factors into account for decision-making. Also, informed consent by the patient and, if they are a minor, their relatives is required before proceeding with this form of treatment.

For patients with certain cancers such as leukaemias, HSCT is usually carried out according to standardised therapy plans (therapy protocols). This can, but does not have to, be done as part of a therapy optimising trial‎. Despite all the "standardisation", each decision is individually tailored to the respective situation and medical history of the patient.

Good to know: before performing a stem cell transplant, the transplant facility always checks whether there is actually an indication‎ for this treatment. It also coordinates the preliminary examinations as well as the preparative treatment (conditioning‎), stem cell collection and follow-up regimen after the procedure.