Understanding the Stem Cell Transplantation Process

It’s common to hear about stem cell transplants in the news, but how do they actually work?
What seems like extremely complicated science is actually much simpler than it seems.

What is a stem cell transplant?

A stem cell transplant is a treatment given to patients of certain types of cancer. Leukemia, multiple myeloma, and certain strains of lymphoma are the most common cancers that respond to stem cell transplants. Occasionally, blood diseases will also be treated in this manner.

Hematopoietic stem cells are capable of evolving into various other types of cells, including more bone marrow cells or any other type of blood cell. These are important within the body; however, various cancers, and some other diseases, are capable of halting these cells from developing as they normally do. When they are impacted in such a manner, the resulting blood cells they create are also defective. Therefore, if you receive a stem cell transplant, you have new stem cells that are able to create new, and healthy, blood cells. This can return you to a greater health standing in certain scenarios.

What is the difference between a stem cell transplant and a bone marrow transplant?

You may have heard the terms stem cell and bone marrow used interchangeably. However, the transplants are slightly different. Stem cells can be collected from bone marrow, so certain patients have indeed received bone marrow transplants that were also stem cell transplants. However, now stem cells are most often taken from blood instead of bone marrow, and stem cell transplants normally refer to this method.

What types of stem cell transplants are there?

Aside from bone marrow, there are many different types of stem cell transplants.

An autologous transplant, sometimes referred to as an AUTO transplant or high-dose chemotherapy with autologous stem cell rescue, is the kind where you actually retrieve your own stem cells after your cancer has been treated. This works by your health care team initially collecting your stem cells from your blood, freezing them, and storing them until after you have completed your chemotherapy or radiation therapy. After, the frozen stem cells will be thawed and reentered into your body via an IV. After approximately 24 hours, the stem cells reach the bone marrow and begin to grow, multiply, and return to their normal function.

Allogeneic transplantations, or ALLO transplants, are where you are receiving stem cells from another person. It is crucial in these situations for the donor's bone marrow to match your own due to a necessity for proteins in your white blood cells, called human leukocyte antigens, to be as similar as possible. If the proteins do not match well enough, you will be at a risk for graft-versus-host disease, which can be very serious, as the healthy transplant cells attack your cells. To avoid this, having a donor within your family, especially a sibling, is normally the best bet. After you receive your chemotherapy or radiation therapy, an IV will administer the healthy stem cells. Unlike in autologous transplants, these cells are usually not frozen. Therefore, you do not have to wait for them to thaw after you complete chemotherapy. ALLO transplants can be ablative (using high-dose chemotherapy), or reduced intensity (using milder doses of chemotherapy).

Read on to learn more about stem cell transplants and how they work.