The life-saving potential of blood stem cells

A 72-year-old Thai patient with acute myeloid leukaemia – a type of blood cancer - had only three more months to live according to the doctor who treated him in Thailand. But, when he consulted Dr Patrick Tan in Singapore, he found a treatment that eventually saved his life.

Haemopoietic stem cell transplant (HSCT) is the procedure that beat his cancer giving him a new lease of life. Nine years after the operation, the patient is still clear of the malignancy.

“HSCT involves the transfer of the earliest source of blood elements known as haematopoietic stem cells to reestablish the body’s blood function,” said Dr Tan, a haematologist at Mount Elizabeth Hospital in Singapore.

He explained that haematopoietic stem cells are responsible for the formation of all types of blood components including red blood cells, white blood cells and platelets.

On top of that, its self-renewing and self-multiplying properties naturally replace damaged blood cells with new healthy ones, thus preserving the immune system.

When a patient is unable to effectively produce or maintain these stem cells on its own, a transplant is considered as a form of therapy.

In the case of the Thai patient, Dr Tan harvested stem cells from the patient’s peripheral blood and injected them back after administering high doses of chemotherapy, which severely affects the blood count - the concentration of blood elements in the body – as well as the immune system.

Thanks to this type of HSCT, also known as rescue therapy, patients are able to deal with high doses of chemotherapy to eradicate aggressive cancer cells because the blood count and the immune system are restored by the stem cells, added Dr Tan.

An additional advantage is that HSCT is not invasive at all. Despite its name, the procedure has more to do with a blood transfusion than an organ transplant. Stem cells are implanted through an intravenous injection on an outpatient basis.

The need for a donor

In many cases patients require a donor because their stem cells are too damaged to replenish blood elements.

For example, some non-malignant blood disorders like thalassaemia and sickle cell anaemia cause a genetic defect that makes patients produce abnormally shaped red cells.

“Once the donor’s stem cells are injected in the patient’s blood stream, they will produce new and healthy red cells,” explained Dr Tan.

This approach works as a gene therapy because it fixes a genetic abnormality.

Obstacles holding back HSCT

HSCTs “can cure more than 90 percent of patients with haematological disorders in the early stage of the disease if an optimal donor-recipient combination is available,” according to the World Health Organization (WHO).

A sibling is usually the most suitable donor to make sure the transplant is successful, according to Dr Tan.

But, patients without siblings have to face a grim reality as the dearth of donors means that they may not access this life-saving procedure.

Although donor registries offer hope to some patients, the chances of getting a genetic match are slim, about one out of 500,000 individuals, according to WHO.

“For those who are lucky enough to find a donor, it can take up to three months,” said Dr Tan.

On top of that, some donors may not be available or may not be willing to donate. From this point of view, cord blood banks are a quicker option because they store stem cells that can be available in a few weeks.  

But, the quantity of cord blood samples is usually too limited to be transplanted effectively in adults. This is why cord blood transplants are often performed in children.

New approach increases the pool of donors  

Haploidentical transplants are providing many patients in search of a donor with a viable alternative.

“Previously we could only find one in three patients with sibling donors,” said Dr Tan

“But haploidentical transplant is becoming an interesting option because it can provide more potential matches.”

This transplant involves using a donor with half-matched genes, which means that the patient’s parents or children could be suitable donors as well.

Dr Patrick Tan is a haematologist at Mount Elizabeth Hospital in Singapore, who is considered a pioneer in the field of haematopoietic stem cell transplant and recognised for performing the world's first successful cases of unrelated HSC transplant and unrelated cord blood transplant for thalassemia major.

Haematology & Stem Cell Transplant
3 Mount Elizabeth, level 7 Mount Elizabeth Hospital
Singapore 228510
Tel: (+65) 6731 2030