Bone Marrow Stem Cells and Other Sources for Leukemia Treatment

Bone marrow transplants for leukaemia have been carried out for decades, although peripheral blood stem cell transplants are being increasingly used. With leukaemia, a patient cannot have their own stem cells harvested prior to chemotherapy as these would simply reintroduce the cancerous leukocytes back into their system, making donor stem cells necessary for treatment. Deriving stem cells from a donor’s bone marrow involves an invasive procedure where needles are inserted into the hip bone (or very occasionally the sternum) in order to aspirate the liquid (marrow) in the center of the bone. This procedure takes approximately an hour and is carried out under either a general anaesthetic or a regional anaesthetic where the patient has no sensation from the waist downward during the procedure. The amount of marrow extracted is usually small enough to not pose any risk to the donor in terms of compromising their immunity but the donor is still at risk of complications from the anaesthesia and the usual surgical risks. The bone marrow is processed to remove blood and bone fragments and the remaining material is usually cryopreserved allowing the stem cells to be stored for many years until needed.

Peripheral Blood Stem Cells for Leukemia

Peripheral blood stem cells are becoming a preferred technique for many, as the procedure is less invasive, requires no anaesthesia, and can allow the collection of considerable numbers of stem cells. Donors of peripheral blood stem cells are likely to be given drugs for several days, or longer, prior to the stem cell harvesting that encourage the stem cells in the bone marrow to enter systemic circulation. These drugs may cause side-effects such as nausea, vomiting, headaches, and weakness, although these usually dissipate after the drugs are ceased at the time of collection. During the procedure a catheter is placed in each of the donor’s arms, or occasionally in the groin, and these are connected to a filtration device that allows the blood to exit one arm, be filtered, and then return to the donor via the other arm. This process is called apheresis, or leukapheresis and takes around 4-6hrs during which the donor may experience some light-headedness, cramping in the hands, chills, and a numbness of the lips; these side-effects of the harvesting can usually be addressed at the time as they are largely due to a depletion of calcium from the circulation. The harvested stem cells can then be frozen for storage and later use in stem cell therapy.

Cord Blood Stem Cells for Leukemia

Umbilical cord blood is also becoming more frequently used to treat cancers such as leukaemia as many parents donate the umbilical cord blood to the National Bone Marrow Donor programme. For many years this blood was only sufficient to treat a child or a small adult but advances in stem cell technology have allowed for a greater yield of stem cells from this source in order to treat fully grown adults. Some researchers are also investigating the possibility of using multiple umbilical cords as sources of stem cells for a single transplant although there are concerns that this may create immunological issues due to varied human-leukocyte-associated (HLA) antigens present from multiple donors. Human umbilical cord blood stem cells have largely been thought immunologically inert or less prone to rejection than adult stem cells taken from bone marrow or the peripheral circulation. In recent years however there have been a number of researchers calling this into question and suggesting that this should not be assumed by those devising stem cell therapies or clinical trials using any kind of stem cells.

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