HAEMATOLOGY

The Transplant Process

Photo of Bone Marrow What is a Stem Cell or Bone Marrow Transplant?

Stem cells are the cells which build and repair tissue and blood systems throughout our body.
Stem cell transplants are a way of eradicating aggressive cancers, for example: leukaemias, lymphomas and some solid tumours, with large or high doses of chemotherapy and on occasion radiotherapy. These high dose therapies not only kill the abnormal cancer cells but also destroy bone marrow. Healthy marrow is taken prior to this and re-infused after the treatment.

Types of Transplants

There are two main types of transplant:
Autologous transplants are when the person's own stem cells are used for the transplant. These can be removed either from the blood or bone marrow, frozen, then returned after high dose chemotherapy. To be successful, it is important for the doctors to be sure that either the cancer has not spread to the bone marrow or that it has been successfully treated before the collection of the stem cells, to reduce the chances of the cancer returning after the transplant.

Allogeneic transplants are when the stem cells used for the transplant are from a matched donor. This is commonly a sibling but in some cases can be an unrelated donor. These transplants are more complicated and carry more transplant related risks.

There are 4 main steps in the transplant process.

Step 1 is to reduce the cancer to as low a level as possible by conventional chemotherapy and/or radiotherapy.
Step 2 is to collect or harvest the stem cells/bone marrow cells. These will then be processed,cryopreserved and stored.
Step 3 is the high dose chemotherapy and/or radiotherapy which is given in an attempt to remove any remaining cancer cells. This is often referred to as "conditioning."
Step 4 is to return the harvested stem/bone marrow cells. The giving back of the stem cells is sometimes called a "rescue". This is because the high dose chemotherapy and/or radiation will destroy most of the bone marrow where normal blood cells are produced. Without the rescue, bone marrow would not be able to produce healthy blood cells again.

Signs that the stem cells are growing in the bone marrow may not be seen for 2 to 3 weeks and it may take a few months before the new bone marrow is producing blood cells adequately.

The Harvest Procedure
Harvest is the term used to describe the collection of stem cells. A peripheral blood stem cell harvest aims to collect these stem cells from the blood. Stem cells will be removed from a person's blood by a special machine called a blood cell separator, or "apheresis" machine.

Occasionally a bone marrow harvest is done instead of a peripheral harvest. This may be a donor or a patient. Bone marrow can also be frozen or given to the patient, fresh.

The harvest usually occurs either after normal chemotherapy or in between chemotherapy courses, using a different chemotherapy drug.
Following chemotherapy, a course of injections is given under the skin called growth factor (G-CSF). Stem cells are collected over several mornings.
It will take between 9 and 13 days for adequate stem cells to appear in the blood to enable harvest.

The Transplant
"Conditioning" is the term used to describe the high dose treatment given to prepare the body to receive stem cells. This is usually chemotherapy and may involve radiotherapy. The previously harvested cells are re-infused back into the body. They are run in through the catheter like a blood transfusion. This is done by a nurse and will take approximately 10 minutes for each bag of thawed cells, although it may take longer if there is a large volume.

Side Effects
Chemotherapy is a toxic substance to the body so will cause side effects. The drugs mainly cause vomiting and effect any cells that divide and replace themselves quickly as cancer cells do. These cells include hair, blood, gut and reproductive cells. Therefore the most usual side effects are nausea and vomiting but some other effects can include:

Hair loss
Low blood counts, increasing your risk of infection and tendency to bleed
Sore mouth - ulcers
Diarrhoea
Organ dysfunction of failure
Infertility
Ovarian failure

This is not a complete list of possible side effects. Each patient responds differently to treatment and it is not possible to predict which problems may occur. Modern drugs enable good control of nausea and vomiting and strong painkillers are used, if necessary, to control symptoms during the transplant.

Length of Stay
The length of stay in hospital depends on the individual. The average stay is 3-4 weeks. Patients remain in isolation until their neutrophil (white cell) count rises. It may only be a week or two in isolation if there are no complications.
After discharge from hospital, patients require monitoring by a haematologist and patients may require blood and platelet transfusions for a few weeks. For several months after the transplant, medications will also be required.

Unfortunately, even with the availability of high dose treatment with transplants, some patients may experience a recurrence of their cancer. Yet, despite the risk of serious complications and relapse, transplantation does offer the hope of cure.