What Is a Stem Cell Transplant?

The simple versionExplain▾

Stem cell transplants are procedures that restore blood 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. They may also be called bone marrow transplants or peripheral blood stem cell transplants.

Blood-forming stem cells are vital because they grow into different types of blood cells:

• white blood cells, which are part of your immune system and help fight infection
• red blood cells, which carry oxygen throughout your body
• platelets, which help the blood clot and prevent bleeding

A stem cell transplant rebuilds your supply of blood-forming stem cells after strong treatment.

Which cancers it treatsExplain▾

Stem cell transplants are most often used to treat people with cancers that affect blood cells, such as leukemia, lymphoma, multiple myeloma, and myelodysplastic syndromes. They may also be used for neuroblastoma, Ewing sarcoma, brain tumors that have come back in children, germ cell tumors, and testicular cancer. They are also used for other blood disorders, such as aplastic anemia and sickle cell disease, and for autoimmune diseases.

How it works against cancerExplain▾

Stem cell transplants do not usually work against cancer directly. Instead, they restore your body's ability to produce new blood cells after treatment with very high doses of chemotherapy and maybe radiation therapy that are used to destroy cancer cells.

But in leukemia, the transplant may work against cancer directly. This happens through an effect called graft-versus-tumor (or graft-versus-leukemia), which can occur after transplants that use stem cells from a donor. This effect occurs when white blood cells from your donor (the graft) attack any cancer cells that remain in your body, improving the chances of success.

The types of transplantExplain▾

In a stem cell transplant, you receive healthy blood-forming stem cells through a needle in your vein. Most transplanted stem cells come from the bloodstream (called a peripheral blood stem cell transplant), but they can also come from the bone marrow (a bone marrow transplant) or umbilical cord blood (a cord blood transplant). Once they enter your bloodstream, the stem cells travel to the bone marrow and take the place of the cells destroyed by treatment.

Transplants can be:

• autologous — the stem cells come from you, the person with cancer
• allogeneic — the stem cells come from someone else, who may be a blood relative or an unrelated but closely matched donor
• syngeneic — the stem cells come from your identical twin

With autologous transplants, the cells will match, but there is a small risk that cancer cells will be transplanted. With allogeneic transplants, the cells must match closely enough that your immune system will not see them as foreign and destroy them. Special forms include mini-transplants (a type of allogeneic transplant using lower doses of treatment) and tandem transplants (a type of autologous transplant with two rounds of high-dose chemotherapy and two transplants).

How donor cells are matchedExplain▾

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

A good HLA match improves the chance that your body accepts donor cells.

Side effectsExplain▾

The high doses of cancer treatment before a transplant can cause bleeding, increased risk of infection, and feeling tired and exhausted.

Short-term problems may include nausea, vomiting, fatigue, loss of appetite, mouth sores, hair loss, and skin reactions. Long-term problems may include infertility, cataracts, new secondary cancers, damage to the liver, kidneys, lungs, or heart, and bone and muscle weakness. Talk with your doctor or nurse about which side effects you might have and what to do about them.

Graft-versus-host diseaseExplain▾

If you have an allogeneic transplant, you might develop a serious problem called graft-versus-host disease. This can occur when white blood cells from your donor (the graft) see cells in your body (the host) as foreign and attack them, damaging the skin, liver, intestines, and other organs.

It can be acute (within the first 3 months after transplant) or chronic (3 months or later). It can be treated with steroids or other drugs that suppress your immune system. The risk can be reduced by using a closer donor match, giving drugs that suppress the immune system, or treating the donated stem cells to remove the T cells that cause it (called T-cell depletion).

What to expectExplain▾

How long it takes. A transplant can take a few months to complete. It begins with high doses of chemotherapy and maybe radiation for a week or two, then a few days of rest. Next you receive the stem cells through an IV catheter, on a day often called "day zero"; this is like a blood transfusion and takes 1 to 5 hours. Then comes the recovery phase, when doctors check your blood counts often. Even after your counts return to normal, full immune recovery takes several months for autologous transplants and 1 to 2 years for allogeneic or syngeneic transplants.

Where you go. For an allogeneic transplant, you will go to a hospital with a specialized transplant center. Transplants require long stays at special centers, and if you do not live nearby you may need to stay in a hotel or apartment when you are not in the hospital.

Working. Whether you can work depends on your job. The process can take many months, with time in and out of the hospital, more tiredness, and frequent hospital visits after discharge. If your job allows, you may want to arrange to work remotely part-time. Many employers are required by law to adjust your work schedule during cancer treatment.