Stem cell transplants are sometimes used to treat lymphoma patients who are in remission (that is, they seem to be disease-free after treatment) or who have had the cancer come back (relapse) during or after treatment.

In a stem cell transplant, doctors give higher doses of chemotherapy (chemo) than would normally be safe. Giving high-dose chemo destroys the bone marrow, which prevents new blood cells from being made. This could normally lead to life-threatening infections, bleeding, and other problems due to low blood cell counts. To get around this problem, after chemo (and sometimes radiation treatment) is finished, the patient gets an infusion of blood-forming stem cells to restore the bone marrow. Blood-forming stem cells are very early cells that can make new blood cells. They are different from embryonic stem cells.

There are 2 main types of stem cell transplants. The difference is the source of the blood-forming stem cells.

Autologous stem cell transplant: For this type of transplant, blood-forming stem cells from the patient's own blood or, less often, from the bone marrow, are removed, frozen, and stored until after treatment. Then the stored stem cells are thawed and given back to the patient through a vein. The cells enter the bloodstream and return to the bone, replacing the marrow and making new blood cells.

This is the most common type of transplant used to treat lymphoma, but it generally isn't an option if the lymphoma has spread to the bone marrow or blood. If that happens, it may be hard to get a stem cell sample with no lymphoma cells in it.

Donor (allogeneic) stem cell transplant: In this approach, the stem cells come from someone else usually a matched donor whose tissue type is very close to the patient's. The donor may be a brother or sister or someone not related to the patient. Sometimes umbilical cord stem cells are used.

This type of transplant is not used a lot in treating non-Hodgkin lymphoma (NHL) because it can have severe side effects that are especially hard for patients who are older or who have other medical problems. And it is often hard to find a matched donor.

"Mini transplant": Many older patients can't have a regular allogeneic transplant that uses high doses of chemo. But some may be able to have what is called a "mini transplant" (or a non-myeloablative transplant or reduced-intensity transplant). For this type of allogeneic transplant, lower doses of chemo and radiation are used so they do not destroy all the stem cells in the bone marrow. The patient is then given the donor stem cells. These cells enter the body and form a new immune system, which sees the cancer cells as foreign and attacks them (called a "graft-versus-lymphoma" effect).

Patients can often do a mini transplant as an outpatient. But this is not yet a standard part of the treatment for most types of lymphoma.

Stem cell transplant is a complex treatment, so it is important to have it done at a hospital where the staff has experience with the procedure. Some transplant programs may not have experience in certain transplants, especially those from unrelated donors.

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