When stem cell transplant is done
People with cancer may have a stem cell transplant for 2 main reasons:
- Stem cell transplant gives the body healthy stem cells when the bone marrow has been damaged by disease or cancer treatments.
- Very high doses of chemotherapy and radiation may be needed to treat certain types of cancer.
- These treatments can severely damage or destroy a person’s bone marrow.
- Stem cell transplant gives someone with cancer (the recipient or host) a new immune system, which attacks remaining cancer cells.
- After an allogeneic transplant, stem cells transplanted from the donor (the graft) identify and destroy any cancer cells that weren’t killed by chemotherapy or radiation therapy.
- The new stem cells’ ability to destroy cancer cells is called graft-versus-tumour or graft-versus-leukemia effect.
- Recipients may have donor T cells infused into their blood (donor leukocyte infusion) to improve this effect.
Deciding to do a stem cell transplant
Doctors consider a number of important factors before deciding to treat cancer with a stem cell transplant.
Younger people often tolerate stem cell transplants better and have fewer complications. Some transplant centres set upper age limits. Age limits may be flexible depending on the person’s general health and other factors.
Overall health and other medical conditions
People who have major health problems, such as heart, lung or kidney disease, may not be suitable candidates for a stem cell transplant.
Doctors consider different aspects of the cancer when deciding to use stem cell transplant, including:
- the type or stage of the cancer
- whether the person is in remission (there are no signs or symptoms of disease) or has had a relapse
- the chance of relapse after transplant
- how sensitive the cancer is to chemotherapy
- Some cancers (such as leukemia, lymphoma and multiple myeloma) respond very well to chemotherapy, but they may not be cured with a standard dose. High-dose therapy may be needed.
- Other cancers do not respond well to high-dose chemotherapy, so this approach is not used.
A stem cell transplant may be used if research shows that this treatment is more likely to cure the cancer than other treatments.
Choosing the type of stem cell transplant
Many factors influence which type of stem cell transplant a person has. Doctors decide to use the person’s own stem cells (autologous transplant) or donor stem cells (allogeneic transplant) based on each person’s needs.
- The person must be able to donate their own stem cells for an autologous transplant.
- A compatible donor must be available for an allogeneic transplant.
To increase the chance of a successful allogeneic transplant and reduce potential complications, doctors use human leukocyte antigen (HLA) typing to match donors and recipients.
- Doctors try to find the closest possible match. They use 6–10 specific antigens in the matching process.
- If the match is not close, donor and recipient stem cells may attack each other.
- The recipient’s immune system may see the donor’s stem cells as foreign and attack them. This is called graft rejection.
- The donor’s stem cells may see the recipient’s cells as foreign and attack them. This is called graft-versus-host disease (GVHD).
- Some people may have uncommon antigens that make it difficult to find a good match.
Doctors carefully consider the benefits and risks before offering a stem cell transplant. Sometimes a stem cell transplant is offered for a disease (such as multiple myeloma) that cannot be cured. In this case, the stem cell transplant can lengthen the period of remission.
A protein found on the surface of all cells, including white blood cells (leukocytes) and platelets, that plays a role in the immune system’s response to foreign substances.
HLAs are typed in a similar way to red blood cells (A, B, O or AB). HLA typing is done before stem cell or organ transplant to make sure that the donor’s tissues match the recipient’s.
Also called human leukocyte-associated antigen or human lymphocyte antigen.
Great progress has been made
Some cancers, such as thyroid and testicular, have survival rates of over 90%. Other cancers, such as pancreatic, brain and esophageal, continue to have very low survival rates.