Stem Cell Transplant Facts

Stem Cell transplants are performed on patients with certain cancers of the blood or bone marrow (e.g. myeloma, leukemia). To help these patients, doctors use hematopoietic stem cell transplantation (HSCT) which is usually derived from bone marrow, or peripheral blood. Although still carrying a high risk, HSCT is still a developing transplantation and is reserved for patients with life-threatening diseases. The use of stem cell transplants has spread beyond cancer to autoimmune diseases and more. These stem cells normally develop into healthy red blood cells, white blood cells and platelets. A bone marrow/ stem cell transplant replaces the stem cells that are cancerous, faulty, or destroyed by chemotherapy or radiation. 

Types of Transplants

The terms “bone marrow” and “stem cell” are sometimes used interchangeably, since bone marrow is the source of hematopoietic stem cells. However, there are technical differences regarding the procedures. 

  • In a bone marrow transplant, stem cells are collected from a donor’s bone marrow directly from the hip bone.
  • In a peripheral blood stem cell transplant (PBST), stem cells are harvested from a donor’s blood through a process called apheresis. Donors receive a medication for five days that increases stem cell production, then stem cells are extracted from the bloodstream in a similar procedure to a blood donation. 
  • An allogeneic transplant requires stem cells from a donor. A donor must have a similar tissue type as the patient. When searching for a donor there is a one in four chance that a patient’s biological sibling will be a good match. However, there are also many organizations that help with matching.
  • In an autologous transplant, a patient’s own stem cells are collected from the blood and frozen, similar to the way a donor’s would be. Sometimes a patient may receive anti-cancer drugs first to reduce the possibility of cancer cells being picked up along with the stem cells.

In both allogeneic and autologous transplants, the patient typically receives high doses of chemotherapy or radiation to destroy the cancer. Finally, the stem cells — either the donor’s or the patient’s own — are given to the patient, and over time they will grow and create healthy blood cells.

The type of transplant a patient receives will depend mostly on the disease being treated. Other important factors are the recipient’s age and health, the stage and status of the disease, the ability to collect and treat the patient’s stem cells, and/or the availability of a donor. For older patients, transplants that do not use high-dose chemotherapy and radiation may be a viable option.

Risks

In allogeneic transplants, the stem cells from healthy donors are cancer-free and can fight any remaining cancer cells (a phenomenon called “graft-versus-cancer”). However, there’s a risk that the donor’s immune cells might attack the patient’s healthy cells (“graft-versus-host disease”). To reduce this risk, patients are usually given drugs to suppress their immune system. However, a weakened immune system can lead to serious infection.

In autologous transplants, because a patient’s own stem cells are used, there is no risk of graft-versus-host disease. There is also a lesser risk of infection. However, there is a possibility that a patient’s cancer cells may contaminate the stem cells.

A patient’s primary care doctor and an oncologist (cancer specialist) or hematologist (blood specialist) will recommend the best treatment options.

-Vlad Elizarov, Alexander’s Hope Intern


Sources:

City of Hope