Blood and Marrow (Stem Cell) Transplant

The simple versionExplain▾

A stem cell transplant is a procedure that restores blood-forming stem cells in people who have had theirs destroyed by the high doses of chemotherapy or radiation therapy used to treat certain cancers, blood disorders, and autoimmune disorders.

Blood-forming stem cells are vital because they grow into different types of blood cells: white blood cells (which fight infection), red blood cells (which carry oxygen), and platelets (which help blood clot).

Stem cell transplants may also be called bone marrow transplants or peripheral blood stem cell transplants, depending on where the cells come from.

A transplant rebuilds your blood-forming cells after high-dose treatment wipes them out.

How it works against cancerExplain▾

Stem cell transplants usually do not work against cancer directly. Instead, they restore your body's ability to make new blood cells after treatment with very high doses of chemotherapy, and maybe radiation, destroys the cancer cells.

There is one important exception. In leukemia, a transplant that uses donor stem cells can work against cancer directly through an effect called graft-versus-tumor (or graft-versus-leukemia). This happens when white blood cells from your donor attack cancer cells that remain in your body, which improves the chances that the transplant succeeds.

The types of transplantsExplain▾

In a transplant, you receive healthy blood-forming stem cells through a needle in your vein. The cells can come from the bloodstream (a peripheral blood stem cell transplant), the bone marrow (a bone marrow transplant), or umbilical cord blood (a cord blood transplant). Once in your bloodstream, the cells travel to the bone marrow and take the place of the cells that were destroyed.

Transplants can be:

• Autologous — the stem cells come from you. The cells will match, but there is a small risk that cancer cells could be transplanted.
• Allogeneic — the cells come from someone else, related or not, if they are a close enough match. It is important that they match closely so your immune system does not see them as foreign.
• Syngeneic — the cells come from your identical twin.

There are also mini-transplants (a type of allogeneic transplant using lower treatment doses) and tandem transplants (a type of autologous transplant with two rounds of high-dose chemotherapy and two transplants).

Which type is right for you depends on many factors, such as your type of cancer, how advanced it is, whether you can use your own cells, whether matching donor cells are available, and your overall health.

Matching a donorExplain▾

To decide if a donor's cells are a match, they are tested for their HLAs (human leukocyte antigens). HLAs are sets of proteins, or markers, found on most cells in your body, and each person has a different set. The more HLAs you and the donor share, the better the chance your body will accept the cells. Most often, the best match for an allogeneic transplant is a brother or sister.

Side effects and graft-versus-host diseaseExplain▾

The high doses of treatment before a transplant can cause bleeding, a higher risk of infection, and feeling tired. Short-term problems can include nausea, vomiting, fatigue, loss of appetite, mouth sores, hair loss, and skin reactions. Long-term problems can include infertility, cataracts, new secondary cancers, organ damage, and bone and muscle weakness.

If you have an allogeneic transplant, you might develop graft-versus-host disease. This happens when white blood cells from your donor (the graft) see your body's cells (the host) as foreign and attack them, which can damage the skin, liver, intestines, and other organs. It can be acute (within the first 3 months) or chronic (3 months or later). It can be treated with steroids or other drugs that suppress the immune system, and the risk can be lowered with a closer match, immune-suppressing drugs, or removing certain donor cells.

Time, place, and recoveryExplain▾

A stem cell transplant can take a few months to complete. It starts with high-dose chemotherapy and maybe radiation for a week or two, followed by a few days of rest. Then you receive the stem cells — the day you receive them is often called day zero. Getting the cells is like a blood transfusion and takes 1 to 5 hours.

After that comes the recovery phase, when doctors check your blood counts often. Even after blood counts return to normal, the immune system takes longer to recover — several months for autologous transplants, and 1 to 2 years for allogeneic or syngeneic transplants. Allogeneic transplants are done at a hospital with a specialized transplant center, and you may need to stay near the hospital during recovery.

A transplant is a months-long process, and your team will follow your blood counts and recovery closely.