Stem Cell Transplants

Hematologic Cancers

Stem cells are immature cells in the bone marrow that mature to become one of three important types of blood cells: white blood cells, which fight infection; red blood cells, which carry oxygen and remove waste products from organs and tissues; and platelets, which enable the blood to clot. Most stem cells are in the bone marrow, but some also reside in the bloodstream. These bloodstream cells, called peripheral blood stem cells are those used in stem cell transplantation.

Because chemotherapy and radiation therapy can destroy vital bone marrow cells, doctors have developed a way to remove some stem cells from patients before such intensive treatment, store them while the patient receives therapy, and then return them to the patient after treatment to help restore the bone marrow's ability to produce the blood cells the patient needs, especially those vital to immunity. The removal and return of a patient's own stem cells is called "autologous stem cell transplantation".

How is a stem cell transplant done?

A process called apheresis or leukapheresis is used to obtain peripheral blood stem cells for transplantation. For four or five days before apheresis, the patient may be given a medication to increase the number of stem cells released into the bloodstream. In apheresis, blood removed from a patient's vein goes through a machine that removes the stem cells. The blood is then returned to the patient, and the collected stem cells are stored. Apheresis typically takes four to five hours to complete. The collected cells may be treated with drugs to destroy any cancer cells that may be present, so that these cancer cells are not returned to the patient during the transplant. The stem cells are then frozen until they are transplanted back to the patient, which is done after the patient completes treatment.

Who gets stem cell transplants?

Stem cell transplantation is performed on patients with Hodgkin's and non-Hodgkin's lymphoma, acute myeloid leukemia, and multiple myeloma, as well as some patients with primary brain cancers. In patients with lymphoma, stem cell transplantation is usually done after an initial course of chemotherapy is completed and the patient experiences a first remission. Patients with acute myeloid leukemia may undergo stem cell transplantation after a first remission or a subsequent remission following a second or later course of chemotherapy. Patients with myeloma may have a stem cell transplant right from the start of their therapy.

Stem Cell Transplant

A stem cell transplant is a complex procedure to replace unhealthy stem cells with healthy ones. Find out what the process is like, including conditioning, and what complications may arise.

When you think of a transplant, you may have an image of a major surgical procedure to replace a diseased organ. But stem cell transplants don't involve surgery. And the "organ" involved is bone marrow, not a solid organ such as a liver. If your bone marrow stops working, your body won't produce enough healthy stem cells. And that means you may not have enough healthy white blood cells, red blood cells or platelets, putting you at risk of life-threatening infections, anemia and bleeding. A stem cell transplant is the infusion of healthy stem cells into your body. If all goes well, these healthy stem cells take hold in your body and begin normal production of blood cells.

Although the procedure is generally called a stem cell transplant, it's also known as a bone marrow transplant or an umbilical cord blood transplant, depending on the source of the stem cells.

What are the reasons for a stem cell transplant?

Stem cell transplants are used to treat people whose stem cells have been damaged by disease or treatment of a disease. Stem cell transplants can benefit a variety of both cancerous (malignant) and noncancerous (nonmalignant) diseases. For instance, in aplastic anemia, a noncancerous condition, your bone marrow stops making enough new blood cells. A stem cell transplant destroys the dysfunctional marrow, and healthy stem cells are infused. If all goes well, the new stem cells migrate to the marrow and begin working normally.

Similarly, in leukemia, the unhealthy bone marrow is destroyed because it doesn't work properly and may contain cancer cells. When healthy stem cells are transplanted, normal cell production can resume. In addition, immune factors in the transplanted cells may help destroy any cancer cells that remain in your bone marrow.

How do you prepare for a stem cell transplant?

Usually you remain at home until your transplant is actually scheduled. During that time, your health care team may recommend that you work on building up your strength and maintaining a healthy diet.

Pre-transplant tests and procedures

Once donor stem cells become available, you undergo many tests and procedures to assess your health and the status of your condition, and to ensure that you're physically prepared for the transplant.

In addition, an intravenous (IV) catheter is typically surgically implanted, usually in your chest near your neck. This is often called a central line, and it usually remains in place for the duration of your treatment. It's through the central line that the transplanted stem cells will be infused. The central line is also used to collect blood samples, give chemotherapy, provide blood transfusions and even supply nutrition when necessary.

The conditioning process

After you complete your pre-transplant tests and procedures, you begin a process known as conditioning. During conditioning, you undergo chemotherapy and possibly radiation in order to:

• Destroy cancer cells
• Suppress your immune system so that your body doesn't reject the transplanted stem cells

The type of conditioning process you undergo depends on a number of factors, including your disease, overall health and the type of transplant planned — whether you get stem cells donated from someone else (allogeneic transplant) or whether the stem cells come from your own body (autologous transplant).

Conditioning generally occurs in the week leading up to your stem cell transplant. In some cases, you receive high doses of chemotherapy and total body irradiation (TBI). On the other hand, you may receive only high doses of chemotherapy and no radiation at all. The type of conditioning you undergo depends on your unique circumstances.

The conditioning process may be done in the hospital or on an outpatient basis. It can cause numerous side effects and complications because your bone marrow and stem cells are destroyed in anticipation of the transplant, and even if your conditioning process is outpatient, you may need hospitalization for side effects.

Side effects of the conditioning process can include:

• Nausea and vomiting
• Diarrhea
• Hair loss
• Mouth sores or ulcers
• Infections, such as pneumonia
• Bleeding
• Infertility or sterility
• Premature menopause
• Anemia
• Fatigue
• Cataracts
• Organ failure, such as heart, liver or lung failure
• Secondary cancers

You may be able to take medications or other measures to reduce such side effects.

'Mini' stem cell transplants

A less intense conditioning process is available through what's known as a "mini" stem cell transplant. It's also called a reduced-intensity conditioning transplant or a non-myeloablative transplant. Reduced-intensity conditioning doesn't try to kill all of the cancer cells that may be in your body. Instead, it relies on the donor's immune system cells to fight your cancer cells.

A less intense conditioning regimen may seem attractive because it may pose fewer life-threatening complications. But this kind of transplant isn't appropriate for all situations. Mini stem cell transplants are typically used only for people who can't endure the harsher conditioning regimen, such as older adults or people in poorer health, and for people whose disease isn't rapidly progressing. In some cases, they may not be as successful as full transplants.

Apheresis

What is Apheresis?

Apheresis is the process of extracting blood components from the peripheral blood with the help of an apheresis machine. This machine is a centrifuge that separates blood into its components on the basis of weight. The machine can be used to obtain plasma (the liquid of the blood), platelets (see Blood Transfusion pamphlet), or white cells. For stem cell transplantation, white cells are collected during the apheresis procedures. A small percentage of these white cells are stem cells, which can restore bone marrow function. Stem cells are mother cells from which several different types of blood cells arise. When stem cells are infused into a patient's bloodstream, they will travel to the inside of certain bones and begin producing cells that eventually mature into red blood cells, white blood cells, and platelets.

How is Stem Cell Apheresis Done?

During apheresis, the patient or donor is connected to the apheresis machine. In the case of a donor, a needle is inserted into a vein in each arm. Blood is withdrawn from one arm, run through the machine to extract the stem cells, and all the remaining components of the blood are returned to the donor through the needle in the other arm. In the case of a patient donating their own stem cells, this process is performed using a central venous catheter, which has two lumens (two tubes within one catheter; see the Linecare pamphlet). Occasionally, the veins of a donor are so difficult to access that a temporary pheresis catheter in the chest or the groin becomes necessary.

What Are Possible Complications?

The actual apheresis process is painless. Patients may experience some lightheadedness, numbness or tingling of the nose, lips, or fingers, but these symptoms are short-lived and easily treatable. To collect sufficient stem cells, the apheresis process must be performed for at least two consecutive days, although five or more procedures may be necessary. Each apheresis procedure takes from three to four hours. Possible complications include bleeding at the needle sites, clotting in blood vessels used for collection (thrombosis), or surgical complications if a temporary apheresis catheter needs to be inserted. Since the procedure involves penetrating the skin, and open access to blood vessels, infection is always a risk.

Why Peripheral Blood Stem Cells?

There are several reasons and advantages for using peripheral blood stem cells (PBSC) instead of bone marrow for transplantation. Sometimes PBSC are used to add to the stem cells collected from a bone marrow harvest. Other times, a patient's bone marrow may be contaminated with cancerous cells; PBSC are then used in the hope that these cells are not similarly contaminated. Prior radiation to the pelvic area, or chemotherapy, can also reduce the number of stem cells available for bone marrow harvest. Also, PBSC can be collected without the use of general anesthesia, and the procedure is usually performed on an outpatient basis with little or no discomfort during, or after, the collection. Most importantly, more stem cells can often be collected from the peripheral blood than from the bone marrow. As a result, blood count recovery is faster after PBSC transplant than after bone marrow transplant. This faster recovery translates into a lower risk for the transplant and fewer complications.

 

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