How transplants work
Doctors and researchers at Fred Hutchinson Cancer Research Center pioneered bone marrow transplants to treat cancers and blood-related diseases four decades ago. Today, at Seattle Cancer Care Alliance (SCCA) and Fred Hutch, we continue to refine transplant techniques and to develop new options, like non-myeloablative transplants, that make this potentially life-saving treatment available to many more people who need it.
Making blood and marrow healthy
Normally, bone marrow makes young blood-forming cells, called hematopoietic stem cells, that develop into mature white or red blood cells or platelets. White blood cells fight infection. Red blood cells carry oxygen to other cells. Platelets help your blood to clot.
“Hematopoietic” means “related to the formation of blood cells.” On average, a small number of hematopoietic stem cells produce an ounce of new blood, about 260 billion new cells, every day.
But certain diseases can disrupt your bone marrow. They may cause your marrow to fail, to produce an excess of some blood cells or to make blood cells that don’t mature and can’t perform their normal functions.
Frequently Asked Questions (FAQs)
To treat blood, marrow or immune system diseases using a transplant, doctors collect and store hematopoietic stem cells, either from a donor or from the transplant patient themselves. The patient receives chemotherapy, total body irradiation or both to destroy or weaken the malfunctioning cells in their body. This is called conditioning. Then doctors infuse stem cells into the patient’s bloodstream. The transplanted cells migrate to their bone marrow to grow and develop, a process called engraftment.
In a high-dose transplant, you get conditioning designed to eliminate your cancer cells and disable your immune system if you have cancer and to destroy your bone marrow if you have a different marrow-related disease.
After conditioning, your body cannot form new blood cells and your immune system cannot protect you as it usually would. Engraftment means your body resumes making blood cells and you develop an immune system again from the transplanted cells.
In a reduced-dose transplant, you get lower-dose conditioning designed to weaken, but not destroy, your bone marrow and immune system so your body will accept the donor’s stem cells.
During engraftment, a new (transplanted) immune system develops alongside your remaining (but weakened) immune system. The goal is for the new immune system to attack cancer cells that survived conditioning and to take over completely as time goes on.
Reduced-dose conditioning makes transplant an option for people age 60 or older and younger people with other health problems, who might not be able to withstand high-dose conditioning.
Different names for transplants
You may see transplants called by one of these names:
- Bone marrow transplant (BMT) — which uses stems cells taken from bone marrow
- Peripheral blood stem cell (PBSC) transplant — which uses stem cells taken from blood circulating around the body
- Cord blood transplant — which uses stem cells collected from umbilical cord blood donated by a mother right after her baby’s birth
- Blood or marrow transplant or stem cell transplant — general terms for a transplant of blood-forming stem cells (whether they come from marrow, circulating blood or cord blood)
- Hematopoietic cell transplant (HCT) — a more technical term for a transplant of blood-forming stem cells
Because the first HCTs were done using bone marrow, many people are most familiar with the term “bone marrow transplant,” and they use this term regardless of the source of the stem cells. For simplicity, we use “bone marrow transplant” in this general sense.
Types of bone marrow transplants
For some diseases, doctors can remove stem cells from a patient and then put these cells back into the patient after conditioning. This is called an autologous transplant. If you are having this type of transplant, you do not need to find a donor; you are your own donor.
For some diseases, you cannot use your own stem cells in a transplant. To have a chance at recovery, you need cells donated by someone else who is healthy. This is called an allogeneic transplant. There are several options, which mean nearly everyone who needs a transplant can receive one.
- Related donor transplant — Typically patients begin by trying to identify a relative to be their donor. Siblings are most likely to be a close match (based on HLA typing).
- Matched unrelated donor transplant — If you don’t have a relative available who is a match, doctors can search international donor registries for an unrelated donor.
- Haploidentical transplant — If you have not been able to find a closely matched donor, you may be able to receive stem cells from a donor who is a half-match for you. This option broadens the pool of potential donors. Haploidentical, or half-matched, transplants rely on advances in drug therapies to prevent graft-versus-host disease (GVHD).
Learn More About GVHD
- Cord blood transplant — Stem cells from donated cord blood don’t need to match you as closely. The immune cells in cord blood are not yet trained to fight foreign invaders, like bacteria, so they’re less likely to interact adversely with your tissues. Normally, a unit of cord blood doesn’t have enough stem cells for a transplant in an adult. But doctors can combine units of cord blood and also greatly expand the number of cells per unit using specialized techniques in the lab.