How stem cell transplants can be used to treat leukaemia

Leukaemia is a cancer which causes large numbers of abnormal white blood cells to be made.

It can be cured or kept under control for many years using chemotherapy as the main treatment.

However for a small number of high-risk patients who are not cured by standard chemotherapy, a stem cell transplant may be required.


But what are stem cells and how can they be used to treat leukaemia?



What are stem cells?

Stem cells are immature cells that develop into specialised cells of the body including those of the blood, heart, liver and brain.



What happens in leukaemia?

Leukaemia is a cancer of the bone marrow.


In people with leukaemia, stem cells in the bone marrow fail to mature properly into white blood cells.

The resulting poor immune system means people with leukaemia suffer from frequent infections.


The abnormal white blood cells also crowd the bone marrow and disrupt the production of other types of blood cells causing anaemia, bruising and bleeding.



How can stem cells treat leukaemia?

A stem cell transplant involves administering high doses of chemotherapy (and sometimes radiotherapy) to destroy the cancerous cells in the bloodstream and bone marrow.


New stem cells infused via a drip eventually settle in the bone marrow and begin producing healthy blood cells.


A stem cell transplant is only considered for a small number of high-risk patients who are not cured by standard chemotherapy.


Stem cell transplants can also be used in many other medical conditions.



What are the risks of stem cell transplants?

A stem cell transplant is a serious medical procedure that takes weeks or months to complete.

Because the chemotherapy does not selectively kill cancerous cells, healthy blood cells of the bone marrow are also destroyed in the process.


Before healthy blood cells start being produced, infection, anaemia and bleeding can occur. Antibiotics and platelet transfusions are given to prevent such complications.


The new immune cells sometimes also see the body's own cells as foreign and attack them.


This complication, called Graft-versus-host disease, can seriously damage the organs and cause death.


Anti-rejection medications are given as preventative therapy.



How are stem cells collected and stored?

A successful stem cell transplant requires a good genetic match between the patient and the stem cell donor.


The best match is usually a sibling, but there is still only a 25 per cent chance of matching. If no sibling donor is available, doctors can search the public registry of stem cells.


Collecting stem cells involves either taking blood from the donor's vein or extracting bone marrow under a general anaesthetic.


Stem cells can also be taken from the placenta and umbilical cord of newborn babies and presents no risk to the mother or baby.


Cord stem cells can be stored in special freezers (cryo-preserved) and used many years later.

The exact expiry date of cryo-preserved stem cells is unknown, but is thought to be indefinite.



What are the latest advances in stem cell therapy?

According to Dr Francoise Mechinaud, director of the Children's Cancer Centre at the Royal Children's Hospital in Melbourne, cord stem cell transplants present some difficulties because the number of stem cells collected at birth is limited.


The fewer stem cells that are infused, the longer the period of recovery.

Doctors are working on techniques to increase the number of stem cells in the cord blood to increase transplant success rates.


New gene-modifying techniques developed within the last two years mean biological parents can now also donate stem cells to their children despite only being a "half match". 


LFLN REF: 15072016, p. 52-53