People struggling with cancer may undergo an allogeneic stem cell transplant, which involves replacing unhealthy stem cells with new ones. Because using a patient’s own stem cell can be unpredictable, many patients use donated bone marrow stem cells for this procedure. If successful, the procedure can help fight off cancer and leukemia. Find out what allogeneic stem cell transplant is, including how it works, as well as the risks and benefits involved with the procedure.
Allogeneic Stem Cell Transplant and How It Works
In this article:
- How Allogeneic Stem Cell Transplant Works
- Where These Stem Cells Come From
- What About Umbilical Cord Blood?
- Why Stem Cells Work
- What Happens During the Process?
- Conditioning Treatment
- Doctors Collect the Stem Cells
- Transplant Happens
- The Cells Go to Work
- Managing Side Effects
- Know About GVHD
- Consider a Mini-Transplant
- What Happens After Transplant
How Allogeneic Stem Cell Transplant Works
In this procedure, doctors extract stem cells from a matching, healthy donor. They then transplant those cells into a person who is ill. The transplanted cells work to suppress the disease. Over time, they work to replace and restore the person’s immune system. The key difference here is where the stem cells come from. In an autologous stem cell transplant, the stem cells come from the patient’s body. In an allogeneic stem cell transplant, they come from another person.
Where These Stem Cells Come From
This procedure can be very effective. How effective depends on how well the stem cells match. Every person’s body is unique. Their DNA and blood type differ. It is important for doctors to match the donor and patient as closely as possible. The closer the match, the more likely the procedure will be effective.
A successful match can happen from various donors. Doctors can include any person who has an HLA-match. A sibling or family member is the most likely option. It is possible to find a very specific, targeted stem cell match in an unrelated donor. This can be rare. However, unrelated people may still be an option. A final option is an unrelated umbilical cord blood match. This too can be challenging. However, more people are banking umbilical cord blood today. Some donate it to a public cord blood bank, while others store it privately for a fee. In these cases, it can help a person to get the care they need.
Doctors have access to donor registries. These are banks of people who sign up to act as a donor. To determine the match, tissue typing occurs. This process involves the use of human leukocyte antigens. Researchers refer to them as HLA. These are proteins. The proteins are in a person’s white blood cells, as well as tissues. Doctors extract tissue samples from both the patient and the donor. They then compare the stem cells in each. A match occurs when the tissue type and blood sample match.
What About Umbilical Cord Blood?
As noted, it may also be possible to use umbilical cord blood. This is an umbilical cord blood transplant. There are some key benefits to this. First, the stem cells here are younger. They are not as mature as others. This means the cells are able to mature more effectively into various types of new cells. Another benefit is their preservation. Doctors harvest the cells at the time of birth. Then, they freeze them. This protects the stem cells from any type of aging. It also prevents environmental factors from impacting the quality of the cells.
This difference is important. Whereas other stem cells from donors must match very closely, this is not the case for umbilical cord blood. There is less tissue typing necessary. In some people, this also helps increase the chances of success. It can also help reduce complications.
The limitation here is access. Umbilical cord blood is not as readily available as other products. This limits the number of patients who can access it. However, as more patients and parents publicly bank cord blood, this may improve. Researchers continue to look for ways to do this. The more readily it occurs, the more units that will be available for therapeutic use. This can help save lives. It can also help patients without a viable match to have a solution. This again, saves those individuals’ lives.
Why Stem Cells Work
Imagine learning a child suffers from leukemia. The body’s treatment options have limits. Many times, the only option is a bone marrow transplant. Yet, a match is necessary. Once found, doctors work to type the tissue and blood. Only when a match is possible can the procedure move forward. But, what happens then? Why does this work?
In a person with a condition like this, the bone marrow or other cells do not work properly. The goal is to replace them with cells that do work properly. Once in place, the new donor cells begin producing red blood cells. They also produce platelets and white blood cells. Over the course of time, this helps develop healthy bone marrow. A key component of the process is the development of new white blood cells. These cells will carry the donor’s immune system to the patient. This healthy immune system then can go to work. It aids the body in getting rid of any leukemia or cancer cells lurking in the body.
What Happens During the Process?
Consider the process patients go through in order to obtain this type of life-saving treatment. First, recognize not all cancer centers or doctors offer this care. Only specialized doctors and locations can offer it. Once a person is in such a treatment, there are numerous steps that occur. These steps prepare the patient for the stem cells.
Before getting the stem cells, patients go through a conditioning process. The goal is to destroy as many cancer cells as possible in the body. This is usually an intense process. However, it also helps to provide the new stem cells with the best possible chance of success. Doctors will use a high dose of chemotherapy drugs to do so. Sometimes, radiation therapy is a part of the process. Some locations also use antibody therapy. The type of drugs and radiation used depends on the type and location of the cancer cells. The actual severity of the condition also plays a role. Some people may be too sick to withstand this conditioning treatment.
Doctors Collect the Stem Cells
Doctors will then collect the stem cells from the donor. This happens alongside the conditioning process. The collection comes from the donor’s blood or bone marrow.
Usually about two days after the conditioning treatment, the stem cell transplant takes place. Most of the time, doctors will use an IV to administer them. The process here is just like getting a blood transfusion. It is not often doctors will administer stem cells directly to the bone marrow. The process does not take long.
The Cells Go to Work
From here, the stem cells move through the bloodstream. They work right away to create new blood cells. The stem cells move into the bone marrow in a process called engraftment. The new cells begin to replace the existing cells. They work to replace the damaged cells in the body. And, they begin working to boost a person’s immune system.
During this period, most patients need an intense amount of care. It is very important that the patient is in a sterile environment. Their immune system is no longer present. And, they will feel weak from the intense therapies given. Doctors will test throughout the process to determine how well the new stem cells are working.
Managing Side Effects
The actual process of transplanting stem cells does not cause many complications. However, the use of intense drugs and radiation beforehand can. Most patients are very weak and struggle as a result. Individuals also need constant monitoring for infection. If an infection occurs, it can be difficult for the body to overcome it. Remember, there is no immune system present.
Patients may need supportive care during this process. This may include additional blood transfusions. There is the risk of potential blood loss from bleeding problems.
Know About GVHD
Another key concern related to allogeneic stem cells transplant is GVHD. More specifically, it is graft-versus-host-disease. The name offers some insight into what this condition is. When it happens, the donor’s stem cells attack the patient’s body. This can create devastating results. There are medications available to reduce some of this risk.
The best way to avoid it is in proper tissue typing. It is essential the donor and patient’s stem cells match as closely as possible. This reduces the risk of GVHD occurring. Doctors will monitor for this condition after the transplant. It may be evident right away. In other cases, it can take time before it becomes clear.
Consider a Mini-Transplant
Some locations offer a mini-transplant procedure. This is not the most common option. It may not work well in some patients. However, it offers less risk. The process starts with chemotherapy, but at a much lower dose. As noted, the condition treatment often creates the biggest risks for patients. This means the drugs work to reduce some of the patient’s bone marrow. It does not destroy it all. The second component is the use of immune system suppression. Doctors will work to keep the person’s immune system suppressed. This help to reduce risks. It also helps to stop rejection from occurring.
The doctors then transplant the stem cells from the donor. At this point, the cells begin to engraft. This is the same basic process as other methods. However, this process can cause graft versus tumor effect. This is a desirable occurrence. It means the stem cells are working to destroy the cancer cells in the body. This is a more direct method. In previous methods mentioned, the transplant leads to a boost in the immune system. Then, the immune system attacks the few remaining cancer cells. Here, the process differs.
The graft versus tumor effect occurs. The stem cells work to destroy the existing cancer cells. During this process, you may receive lymphocytes. These are immune cells. They come directly from the stem cell donor. This boost helps the body to fight existing cancer cells more effectively. It is not always done. It is a DLI procedure. This stands for donor lymphocyte infusion.
What Happens After Transplant
Over time, the donor’s stem cells grow. They multiply and replace the existing bone marrow. The length of the hospital stay depends on many factors. A key concern is the number of side effects. Some patients have few. Others have a significant amount. Doctors will work to minimize these. Then, the patient must get stronger before being able to go home.
Watch how allogeneic stem cells transplants work with this animated video:
Allogeneic stem cell transplant can be very effective for some individuals. As noted, it is a newer treatment and, therefore, not as readily available. However, it allows for a safe method of overcoming cancer. There are risks, but they tend to be lower than others. Patients who are struggling with cancer or leukemia may wish to seek out a location specializing in this type of care.
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