A stem cell transplant may be used to treat non-Hodgkin lymphoma (NHL). A stem cell transplant replaces a person's stem cells. It is used to restore bone marrow when it has been damaged by disease or destroyed by high doses of chemotherapy or radiation therapy. A stem cell transplant may also be called a bone marrow transplant.
Stem cells are the basic cells from which all our blood cells develop. They are found in the bone marrow and in the bloodstream.
At one time, the bone marrow was the most common source of stem cells for transplant (bone marrow transplant). Now blood is being used more often as the source of stem cells (peripheral stem cell transplant).
Stem cell transplants may be considered for people with NHL in the following cases:
There are 3 basic types of stem cell transplants that may be used with NHL.
The stem cells are taken from the person's own bone marrow or blood. An autologous transplant is the most common type done for NHL. There are advantages to having an autologous stem cell transplant, such as avoiding graft-versus-host disease and not needing to find a donor. Many people with lymphoma cannot have an allogeneic stem cell transplant using stem cells from another person (donor) because it can be difficult to find a match. However, an autologous transplant may not be possible for some types of lymphoma that have spread to the bone marrow or blood because it can be difficult to get stem cells that are free of lymphoma. Some people with NHL who have an autologous stem cell transplant will relapse after the transplant.
The stem cells are taken from one person (donor) and are given to another person receiving the transplant (recipient). A donor may be a relative or an unrelated person. The donor and recipient are matched through a process called HLA typing.
One beneficial effect of having an allogeneic transplant is the graft-versus-lymphoma effect in which the donor cells attack remaining cancer cells. However, there are more toxicities and side effects associated with an allogeneic transplant than with an autologous transplant.
It is often hard to find a matched donor for an allogeneic transplant. The side effects of this type of transplant can also be very hard on older people. Therefore, this type of transplant may not be done as often for NHL.
The stem cells are taken from a donor who is the identical twin of the recipient. It is an uncommon type of transplant.
A stem cell transplant is a risky and complex procedure. For this reason, stem cell transplants are done in specialized transplant centres or hospitals by a team of highly trained healthcare professionals.
The day the stem cells are given is usually referred to as Day 0. The days after transplant are numbered upward (for example, Day +1, Day +2 and so on). This system is useful to describe the timing of events, such as when new blood cells begin to appear (engraftment) or complications of the procedure.
There are 3 stages in a stem cell transplant procedure.
Before the stem cell transplant, some procedures are done to check that the recipient is a good candidate. If the organs are functioning well and there are no hidden infections or other problems, the person receiving the transplant will be given counselling and signs a consent form for the procedure. Stem cells are collected for the transplant (called harvesting).
The stem cell transplant procedure has 2 steps:
Sometimes lower doses of chemotherapy or chemotherapy and radiation therapy are used to condition a person, particularly if they are older or have medical conditions that do not allow for full doses of therapy to be given. Such transplants are called mini- or non-myeloablative allogeneic transplant. These conditioning therapies are less toxic, so these types of transplants are done more frequently. Mini- or non-myeloablative transplants are only done with allogeneic transplants.
People are watched closely after they receive a stem cell transplant. They are also carefully followed up for a period of time after leaving the hospital. After a stem cell transplant, people are at high risk of infections, are often quite fatigued and may require blood transfusions. They need frequent medical checkups because they received high doses of chemotherapy. It may take several months to fully recover after a stem cell transplant as recipients’ immunity can take more than 6 months to return to normal.