In 1956, the first successful bone marrow transplant was performed by Dr E. Donnall Thomas in Cooperstown, New York. This milestone involved identical twins, with bone marrow taken from the healthy twin, and given to the other, who had leukaemia.
This ground-breaking treatment paved the way for a life-saving therapy that is now standard for patients with blood cell disorders, such as leukaemia, sickle cell anaemia and inherited immune system disorders.
Bone marrow and cancer
Bone marrow is a spongy tissue found in the centre of bones. It contains cells called haematopoietic (or blood-making) stem cells. These stem cells produce millions of blood cells, such as red cells, white cells and platelets, every day. These blood cells are relatively transient; they are produced as required, and when no longer needed, they die.
Haematological (blood cell) cancers, such as leukaemia, usually arise in the bone marrow. A single blood cell that has been mutated (damaged) begins to divide uncontrollably, producing copies of itself that eventually fill the bone marrow and spread through the blood system. Chemotherapy (and sometimes radiotherapy) is used to kill these cancer cells.
Before the advent of bone marrow transplantation, high doses of chemotherapy, sufficient to kill all the cancer cells, could not be used, as they also killed the normal cells in the bone marrow. With the demonstration of successful bone marrow transplantation however, doctors were able to use higher, more effective doses of chemotherapy and radiation. These higher doses also kill normal bone marrow cells, but now these cells can be replaced with donor cells.
Where do donor cells come from?
The first bone marrow transplants were performed in identical twins, and then in siblings, because cells from unrelated donors were rejected by patients. Subsequent research revealed that bone marrow donors and recipients can be unrelated, however their blood cells must be sufficiently similar, or “matched” to avoid transplant rejection. Where possible, it is preferable for matched siblings or other close relatives to act as bone marrow donors. When a matched relative is unavailable, international Bone Marrow Donor Registries exist to match unrelated donors with patients.
Bone marrow is not the only source of haematological stem cells. Blood left behind in a newborn baby’s umbilical cord is also rich in these cells. Cord blood stem cells have some advantages, for example they can be stored when a baby is born, and quickly accessed when needed. There are more than 100 Cord Blood Banks worldwide.
Another source of stem cells is from a donor’s blood, or from the patient’s own blood. This is called a “peripheral blood stem cell transplant”. Collecting stem cells from blood is easier than collecting it from bone marrow, and large numbers of cells can be harvested. Peripheral blood stem cell transplants are increasingly replacing bone marrow transplants. However a doctor will take into account many factors when deciding which type of transplant is most appropriate for each patient.
Since the first bone marrow transplant in 1956, over one million stem cell transplants have been performed worldwide. Thousands of people with blood cell cancers now benefit from this treatment every year.