What Is a Stem Cell Transplant?

High doses of chemotherapy or radiation therapy destroy blood stem cells. A stem cell transplant restores them. Those high doses are used to treat certain cancers, blood disorders, and autoimmune disorders. Transplants 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.

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

Stem cell transplants do not usually fight cancer directly. Very high doses of chemotherapy, and maybe radiation therapy, destroy the cancer cells. The transplant then restores your body's ability to make new blood cells.

But in leukemia, the transplant may fight cancer directly. This happens through an effect called graft-versus-tumor, or graft-versus-leukemia. It can occur after transplants that use stem cells from a donor. White blood cells from your donor, called the graft, attack any cancer cells left in your body. That improves the chances of success.

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. That is called a peripheral blood stem cell transplant. They can also come from the bone marrow, in a bone marrow transplant, or from umbilical cord blood, in a cord blood transplant. Once they enter your bloodstream, the stem cells travel to the bone marrow. There they 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 too. With allogeneic transplants, the cells must match closely enough. Otherwise your immune system will see them as foreign and destroy them. There are two special forms. Mini-transplants are allogeneic transplants that use lower doses of treatment. Tandem transplants are autologous transplants with two rounds of high-dose chemotherapy and two transplants.

Are a donor's stem cells a match? To find out, they are tested for their HLAs, or human leukocyte antigens. These are 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.

The high doses of cancer treatment before a transplant can cause bleeding. They also raise the risk of infection, and leave you feeling tired and worn out.

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, and new secondary cancers. They may also include 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.

One symptom cannot wait. During the weeks when your blood counts are lowest, a fever is an emergency, not a wait-and-see. NCI's transplant guidance treats a temperature of 100.4°F (38°C) or higher as a sign of infection, and infections in this period can be life threatening. Sources word this threshold slightly differently, so use the number your own team gave you. Call the transplant team before taking acetaminophen, because it can mask the fever they need to measure. The low-count period is covered in more detail in infection and neutropenia.

If you have an allogeneic transplant, you might develop a serious problem called graft-versus-host disease. White blood cells from your donor, the graft, may see cells in your body, the host, as foreign. They then attack them, damaging the skin, liver, intestines, and other organs.

It can be acute, within the first 3 months after transplant, or chronic, at 3 months or later. It can be treated with steroids, or with other drugs that suppress your immune system. The risk can be lowered in several ways: by using a closer donor match, by giving drugs that suppress the immune system, or by treating the donated stem cells to remove the T cells that cause it. That last approach is called T-cell depletion.

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 come 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. Your counts return to normal first. Full immune recovery takes longer: several months for autologous transplants, and 1 to 2 years for allogeneic or syngeneic transplants. If nothing goes wrong, you can usually go home about 100 days after receiving donor stem cells.

Where you go. For an allogeneic transplant, you will go to a hospital with a specialized transplant center. Transplants require long stays at these centers. If you do not live nearby, you may need to stay in a hotel or apartment when you are not in the hospital. Travel and housing costs are a real part of the decision, so ask the center what help it offers before you agree.

Working. Whether you can work depends on your job. The process can take many months, with time in and out of the hospital. Expect 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.

• Call 911 or go to an emergency department if you feel faint, confused or short of breath alongside a fever. With blood counts low, an infection can move to sepsis quickly.
• Call the transplant team at once, at any hour, if your temperature hits 100.4°F (38°C) or higher, or you get hard shaking chills. CDC treats a fever after chemotherapy as a medical emergency, and around a transplant it needs antibiotics within about an hour. If you cannot reach them in minutes, go to an emergency department and tell staff on arrival that you have had a transplant. Do not take acetaminophen first.
• Call your care team the same day if you have a cough or sore throat, a stiff neck, redness or swelling where your catheter enters the skin, white patches in your mouth, cloudy or bloody urine, or pain on passing urine.
• Call your care team within a day or two if a donor transplant brings a new rash, ongoing diarrhea, or yellowing of the eyes or skin. Those can be early graft-versus-host disease, and it is treatable.

• National Cancer Institute — Stem Cell Transplants in Cancer Treatment
• National Cancer Institute — Infection and Neutropenia During Cancer Treatment
• CDC — Fever and Cancer Treatment