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Research in stem cell transplant

A stem cell transplant replaces a person’s blood-forming (hematopoietic) stem cells. It is used when bone marrow has been damaged by cancer or by the chemotherapy or radiation therapy used to treat the cancer. With a transplant, higher doses of chemotherapy can be used to kill the cancer cells. The new stem cells will go to the bone marrow and start making new blood cells. Researchers are studying ways to make stem cell transplants safer and more effective.

Most stem cell transplants use stem cells taken from the blood circulating in the body (called peripheral blood) instead of from the bone marrow. The reason is that more stem cells can be taken from peripheral blood than from bone marrow. Also, it’s easier for donors to give peripheral blood stem cells. And the recipient’s blood cell count usually recovers faster.

Reduced-intensity allogeneic transplants

An allogeneic stem cell transplant takes blood or bone marrow from a donor (usually a brother or sister) and gives it to a recipient. Researchers are studying the effectiveness of reduced-intensity allogeneic transplants. They use lower doses of chemotherapy or radiation therapy before the transplant so that these therapies don’t completely destroy the recipient’s bone marrow. In doing this, the blood cell counts may not drop as low as they do in standard stem cell transplants so there may be a lower risk of some complications.

Researchers are looking at ways to improve outcomes with this treatment because reduced-intensity allogeneic transplants are linked with a higher risk that the cancer will come back (recur) than standard stem cell transplants. They are also studying reduced-intensity allogeneic transplants for people who may not be able to handle a standard stem cell transplant, such as those with certain health conditions and older people.

Researchers are also looking at using a reduced-intensity allogeneic transplant after an autologous transplant, which uses a person’s own blood or bone marrow. Giving an autologous transplant before the reduced-intensity allogeneic transplant can help lower the amount of cancer in the body.

Cord blood transplants

Stem cells are collected from the umbilical cord shortly after a baby is born. This cord blood can be stored for the family’s own use later, or it can be donated to a blood bank. In Canada, there are a few cord blood banks that collect and store cord blood. Transplants using cord blood are linked with a lower risk of graft-versus-host disease (GVHD), but it takes longer to recover blood counts.

Cord blood transplants are mostly studied in children. This is because only a small amount of blood is taken from the umbilical cord (50 mL to 100 mL), so fewer stem cells are available for transplant.

Research using cord blood transplants includes:

  • studying who would be most suited for it
  • looking for ways to use cord blood in adults, such as by boosting the number of stem cells in cord blood before they are transplanted
  • looking at using cord blood from 2 newborns (double cord blood transplant)
  • using cord blood in reduced-intensity allogeneic transplants

Tandem transplants

A tandem transplant is also called a double autologous transplant. A tandem transplant means that a person gets 2 autologous transplants. Before each one, high-dose chemotherapy is given.

Tandem transplants are used to treat some types of cancer, but researchers are still trying to decide when it is best to give the transplant and who will benefit most from it. They are also studying tandem transplants to see if they can help lower the risk that the cancer will come back.

New ways of preparing for and managing transplants

Researchers are trying to find the best ways to prepare a person for conditioning treatment and transplant. Conditioning means giving high doses of chemotherapy before the transplant. Studies include looking at:

  • different growth factors or colony-stimulating factors to produce more stem cells and speed up bone marrow recovery
  • improved conditioning procedures, such as different chemotherapy drugs and targeted therapy drugs, or using radioimmunotherapy (a radioactive substance combined with monoclonal antibodies to deliver radiation directly to cancer cells)
  • better ways to prevent and treat side effects of stem cell transplants such as infection, sore mouth (mucositis) and GVHD
  • better ways to remove any remaining cancer cells before stem cells are given back to the recipient in an autologous stem cell transplant
  • how to improve treatments that are given after a stem cell transplant to prevent the cancer from coming back

Using mismatched and haploidentical donors

In an allogeneic stem cell transplant, a donor’s stem cells need to match the recipient’s as closely as possible to increase the chance of a successful transplant and to lower the risk of problems. The best chance of finding a match is from a blood relative, with the greatest likelihood for an identical match being a blood-related brother or sister.

To find out if a donor is a good match, human leukocyte antigen (HLA) testing is done to identify antigens on the surface of a person’s cells and tissues. The antigens on the donated stem cells need to be exactly the same as those on the recipient’s cells or very similar to them.

A haploidentical donor is a half-match family member and can be a mother or father, child, brother or sister, or sometimes a cousin. A biological child or parent is always a half-match to the recipient.

A mismatched donor has few matched antigens but may be an option for people when a good match is not found within the person’s family or in an unrelated donor.

Researchers are studying and comparing transplants with mismatched donors, haploidentical donors, cord blood donors and matched unrelated donors.

Find out more about HLA testing.

graft-versus-host disease (GVHD)

A condition that might happen after a stem cell transplant. Healthy stem cells from a donor (called the graft) attack a recipient’s (receiver’s) cells (called the host). The graft cells see the host cells as foreign and start to destroy them. Symptoms include jaundice, rash or blisters on the skin, dry mouth or dry eyes.

monoclonal antibody

A substance that can find and bind to a particular target molecule (antigen) on a cancer cell.

Monoclonal antibodies can interfere with a cell’s function or can be used to carry drugs, toxins or radioactive material directly to a tumour.


A foreign substance that stimulates the immune system to produce antibodies against it.