A bone marrow transplant is a medical treatment that replaces your bone marrow with healthy cells. The replacement cells can either come from your own body or from a donor.

In this article, Pritish Kumar Halder explains bone marrow and the different types of bone marrow transplants. Also, how it works.

A bone marrow transplant is also called a stem cell transplant or, more specifically, a hematopoietic stem cell transplant. Transplantation can be used to treat certain types of cancer, such as leukemia, myeloma, and lymphoma, and other blood and immune system diseases that affect the bone marrow.

What are stem cells? What is bone marrow?

Stem cells are special cells that can make copies of themselves and change into the many different kinds of cells that your body needs. There are several kinds of stem cells and they are found in different parts of the body at different times.

Bone marrow is soft, spongy tissue in the body that contains hematopoietic stem cells. It is found in the center of most bones. Hematopoietic stem cells are also found in the blood that is moving throughout your body.

For more information about function and structure of bone marrow click here.

What are the different types of transplant?

bone marrow transplant operation

There are different types of bone marrow/stem cell transplants. The 2 main types are:

Autologous transplant

Stem cells for an autologous transplant come from your own body. Sometimes, cancer is treated with a high-dose, intensive chemotherapy or radiation therapy treatment. This type of treatment can damage your stem cells and your immune system. That’s why doctors remove, or rescue, your stem cells from your blood or bone marrow before the cancer treatment begins.

After chemotherapy, the stem cells are returned to your body, restoring your immune system and your body’s ability to produce blood cells and fight infection. This process is also called an AUTO transplant or stem cell rescue.

Allogenic transplant

Stem cells for an allogenic transplant come from another person, called a donor. The donor’s stem cells are given to the patient after the patient has chemotherapy and/or radiation therapy. This is also called an ALLO transplant.

Many people have a “graft-versus-cancer cell effect” during an ALLO transplant. This is when the new stem cells recognize and destroy cancer cells that are still in the body. This is the main way ALLO transplants work to treat the cancer.

Finding a “donor match” is a necessary step for an ALLO transplant. A match is a healthy donor whose blood proteins, called human leukocyte antigens (HLA), closely match yours. This process is called HLA typing. Siblings from the same parents are often the best match, but another family member or an unrelated volunteer can be a match too. If your donor’s proteins closely match yours, you are less likely to get a serious side effect called graft-versus-host disease (GVHD). In this condition, the healthy transplant cells attack your cells.

If your health care team cannot find a donor match, there are other options.

Umbilical cord blood transplant

In this type of transplant, stem cells from umbilical cord blood are used. The umbilical cord connects a fetus to its mother before birth. After birth, the baby does not need it. Cancer centers around the world use cord blood. Learn more about cord blood transplants.

Parent-child transplant and haplotype mismatched transplant. Cells from a parent, child, brother, or sister are not always a perfect match for a patient’s HLA type, but they are a 50% match. Doctors are using these types of transplants more often, to expand the use of transplantation as an effective cancer treatment.

How does a bone marrow/stem cell transplant work?

The information below tells you the main steps of AUTO and ALLO transplants. In general, each process includes collecting the replacement stem cells, the patient receiving treatments to prepare their body for the transplant, the actual transplant day, and then the recovery period.

Often, a small tube may be placed in the patient’s chest that remains through the transplant process. It is called a catheter. Your health care team can give you chemotherapy, other medications, and blood transfusions through a catheter. A catheter greatly reduces the amount of needles used in the skin, since patients will need regular blood tests and other treatments during a transplant.

How does an AUTO transplant work?

Step 1: Collecting your stem cells. This step takes several days. First, you will get injections (shots) of a medication to increase your stem cells. Then your health care team collects the stem cells through a vein in your arm or your chest. The cells will be stored until they are needed.

Step 2: Pre-transplant treatment. This step takes 5 to 10 days. You will get a high dose of chemotherapy. Occasionally, patients also have radiation therapy.

Step 3: Getting your stem cells back. This step is your transplant day. It takes about 30 minutes for each dose of stem cells. This is called an infusion. Your health care team puts the stem cells back into your bloodstream through the catheter. You might have more than one infusion.

Step 4: Recovery. Your doctor will closely monitor your cells’ recovery and growth and you will take antibiotics to reduce infection. Your health care team will also treat any side effects. Read more details below about recovering from a bone marrow transplant.

How does an ALLO transplant work?

Step 1: Donor identification. A matched donor must be found before the ALLO transplant process can begin. Your HLA type will be found through blood testing. Then, your health care team will work with you to do HLA testing on potential donors in your family, and if needed, to search a volunteer registry of unrelated donors.

Step 2: Collecting stem cells from your donor. Your health care team will collect cells from either your donor’s blood or bone marrow. If the cells are coming from the bloodstream, your donor will get daily injections (shots) of a medication to increase white cells in their blood for a few days before the collection. Then, the stem cells are collected from their bloodstream. If the cells are coming from bone marrow, your donor has a procedure called a bone marrow harvest in a hospital’s operating room.

Step 3: Pre-transplant treatment. This step takes 5 to 7 days. You will get chemotherapy, with or without radiation therapy, to prepare your body to receive the donor’s cells.

Step 4: Getting the donor cells. This step is your transplant day. Your health care team puts, or infuses, the donor’s stem cells into your bloodstream through the catheter. Getting the donor cells usually takes less than an hour.

Step 5: Recovery. During your initial recovery, you will get antibiotics to reduce your risk of infection and other drugs, including medications to prevent and/or manage GVHD. Your health care team will also treat any side effects from the transplant. Read more details below about bone marrow transplant recovery.