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Stem-Cell Transplants

A type of treatment that some people can receive for their lymphoma is a Stem cell /Bone Marrow transplant. Stem cell transplants are sometimes used to treat lymphoma patients who are in remission or who have a relapse during or after treatment. Stem cell transplants allow doctors to use higher doses of chemotherapy to kill the lymphoma than normally would be tolerated. Radiation is sometimes given as well. This treatment can kill the cancer cells but also destroys the bone marrow, which prevents new blood cells from being formed.

Types of  stem-cell transplants

There are 2 main types of stem cell transplants (SCTs) based on the source of the stem cells. In an autologous SCT, the patient’s own stem cells are used. In an allogeneic transplant, the stem cells come from someone else (a donor). The donor’s tissue type (also known as the HLA type) needs to match the patient’s tissue type as closely as possible to help prevent the risk of major problems with the transplant.

Autologous SCTs are used more often than allogeneic to treat lymphoma. Still, using the patient’s own cells may not be an option if the lymphoma has spread to the bone marrow or blood. If that occurs, it may be hard to get a stem cell sample that is free of lymphoma cells.

The use of allogeneic transplants is limited in treating lymphoma because they can have severe side effects that make them hard to tolerate, especially for patients who are older or who have other medical problems. It can also be hard to find a matched donor.

The early complications and side effects from a stem cell transplant are basically the same as those caused by any other type chemotherapy only they tend to be more severe. As such, they are not an option for everyone. Various factors, including age, medical history, type of lymphoma and response to previous therapies are considered 

Where do the transplanted stem cells come from?

Stem cells are transplanted into a person after myeloablative therapy (chemotherapy or radiation therapy that destroys the stem cells in the bone marrow).

The transplanted stem cells can come from two sources:

  • Autologous stem cell transplant: the person themselves provides the stem cells before they receive the myeloablative (high dose) treatment
  • Allogeneic stem cell transplant: the stem cells are provided by a compatible donor, such as a sibling

Autologous stem cell transplants are more commonly performed in the management of lymphoma as they are better tolerated by the person with cancer.

How are transplants performed?

Four steps are involved in a stem cell transplant (BMT or PBSCT):

1. Harvesting stem cells or bone marrow

  • Harvesting is the procedure by which the bone marrow or stem cells are obtained in preparation for the transplant. In a BMT, the stem cells are withdrawn from the bone marrow by inserting a needle into a bone in the pelvic region (hip). The bone marrow is then filtered and stored until the day of the transplant.
  • In a PBSCT, stem cells are taken from the bloodstream, a far easier and more commonly used option. The stem cells are separated from other components of the blood in a process called apheresis, and the rest of the blood is returned to the patient.

2. Processing/preserving the stem cells or bone marrow

  • Stem cells or bone marrow harvested from the person (autologous transplant) are usually stored in a freezer until ready for use. Stem cells or bone marrow derived from a donor (allogeneic transplant) are usually collected immediately before use and not stored for any length of time.

3. Administering myeloablative therapy

  • High-dose chemotherapy, with or without myeloablative radiation therapy, is then administered to the person to destroy the cancerous cells, as well as the healthy cells in the bone marrow.

4. Reinfusing harvested stem cells or bone marrow

  • The harvested stem cells or bone marrow (obtained from either the person's own healthy cells or from a donor) are then transplanted intravenously into the person's bloodstream. The stem cells travel through the body to the bone marrow where they settle and begin to produce new, healthy blood cells.
  • Eventually, they will produce enough healthy cells to repopulate the whole bone marrow, replenishing all blood and immune cells. In the period of time between the myeloablative therapy and the transplanted stem cells beginning to make new blood cells, the person is at an increased risk of infection and bleeding complications, and must be closely monitored.

Patient receiving stem cell transplant

What are the side effects of transplants?

Transplants are very strenuous procedures and take weeks or months to complete. They also take a large toll on the body. As such, they are not an option for everyone. Various factors, including age, medical history, type of lymphoma and response to previous therapies are considered.

A major risk associated with transplants is infection, due to the loss of immune function from the myeloablative therapy. Excessive bleeding is also a concern due to the loss of platelets (necessary for effective blood clotting). Both of these side effects are treatable, with antibiotics given to prevent infection and platelet transfusions to prevent bleeding. Transfusions of red blood cells may also be required to treat anaemia.

Some side effects of stem cell transplant are similar to those seen with chemotherapy and radiation therapy, such as nausea, vomiting, fatigue, loss of appetite, mouth sores, hair loss and skin reactions. These are mainly due to the side effects of the myeloablative therapy. Some long-term side effects of myeloablative therapy can include infertility (the inability to have children), cataracts (a clouding of the lens of the eye that can result in decreased vision), and damage to various organs including the liver, kidneys, lungs and heart, and the potential for a new cancer to develop.

A complication called graft-versus-host disease (GVHD) can occur with allogeneic transplants. The immune cells from the donated tissue (called the graft) can react against the cells of the person who received the transplant (the host) and attack them. This can cause damage to the person's organs, including skin, liver and digestive tract. This reaction can occur within a few weeks of the transplant procedure (called acute GVHD), or much later (called chronic GVHD). GVHD can be serious and difficult to treat. Doctors commonly try to prevent it ahead of time using medications and specific procedures that can reduce the immune reaction of the donor and the recipient.

Stem Cell Transplant