Stem Cell Transplants
Doctors use three main types of stem cell transplants for treatment for various diseases:
- Allogeneic transplants
- Autologous transplants
- Syngeneic transplants
This type of transplant uses bone marrow stem cells from a “matched” donor, whose cells closely resemble the patient’s own. In most cases, these cells come from an immediate relative (brother or sister), but can also come from a national public registry.
Allogeneic transplants boost the immune system, which helps destroy diseased cells. When using cells from outside donors, doctors can always transplant more cellular units if the patient needs them, and healthy donated cells are always free of cancer.
However, there are some risks to allogeneic transplants. There is always the chance the transplant won’t work and the donated cells may attack the host’s body. Called graft-versus-host disease, this side effect often disappears over time, but may get much worse instead. Patients also have a higher chance of outside infection during a transplant.
Recently, doctors started using stem cells from the umbilical cord for treatments, since these cells are powerful and multiply quickly. These cells also don’t require an exact match, so patients have more treatment options. Researchers are also looking into new therapies using cord blood, including taking cells from two different donors, or multiplying donated stem cells before a transplant.
Some patients can’t give up much bone marrow for a transplant, due to age or health conditions. In these situations doctors often utilize a mini transplant, which uses less chemotherapy. This process eliminates both cancer and stem cells, and increases the chance for a successful transplant, since the immune system is temporarily stunned.
While the host’s cells still exist in this situation, both cell types – the host’s and the donor’s – are active in the body at the same time. When the donated cells take over, they have enough resistance to fight off diseased cells. Since this method uses less chemotherapy, blood cell counts don’t drop as greatly and recovery time is lessened.
While the mini transplant method is effective with certain cancers, many fast-growing or late-stage cancers need a full transplant. These conditions often require much heavier amounts of chemotherapy and radiation therapy, so light amounts of chemo don’t eliminate enough cancer cells.
Doctors are continuing research on mini transplants and experimenting with new treatment methods, such as “combination therapy.” After a patient receives an autologous transplant – using their own cells – they can receive donated cells. This type of therapy is called a tandem transplant, and is effective with certain diseases, like multiple myeloma.
Although allogeneic transplants are the most common, many patients can use their own cord blood cells for treatment instead.
For an autologous transplant, doctors will use your own stem cells for your treatment. They begin by taking cells from your bone marrow, peripheral blood or stored cord blood. After medical therapy, your stored cells are injected back into your veins, where they make their way to the damaged area, speeding up the body’s healing process.
Since these cells are from your own body, they won’t cause graft-versus-host disease – which is when the donated cells attack the host’s body. There is also no chance of infection from an outside donor, since the cells are your own.
Doctors typically use autologous transplants as a treatment for leukemia, lymphoma, and similar disorders. While these therapies treat certain cancers, like testicular cancer and several children’s cancers, doctors are still looking for more effective treatments. Autologous transplants are currently in clinical trials for several major diseases, including multiple sclerosis, Crohn’s disease, and systemic sclerosis.
Autologous transplant therapy
The biggest disadvantage with this type of transplant is the danger of diseased cells being extracted along with stem cells. When doctors remove stem cells from your bone marrow or blood, there is a small chance they can accidentally remove damaged cells with them. This means certain conditions, like cancer, can easily form again since your immune system didn’t suppress them the first time.
Doctors may use medications on your stem cells to prevent dangerous side effects. This is referred to as “purging.” However, this can harm stem cells by stunting new blood cell growth and increasing chances for dangerous infections. White blood cell counts may also become unstable from damaged stem cell transplants.
For diseases like cancer, many doctors will remove stem cells, transplant them again without treatment, and give the patient cancer medicine later. This keeps stem cells healthy, and allows the doctor to remove leftover cancer cells at a later date when the patient is more stable. However, all of these treatments are currently under research, and doctors continually find new therapies for cancer treatment using autologous stem cells.
Doctors sometimes use two autologous transplants in a row, which is called a tandem transplant. Patients receive two rounds of chemotherapy, with a stem cell transplant taking place in between each chemo session. The total therapy takes about six months and allows doctors to treat cancer cells while also transplanting healthy new cells into the body.
The problem with this therapy is the risk. Two different transplants means twice the risk of infection and other major side effects. While researchers are still looking for new treatments using tandem transplants, doctors often use this therapy for patients with testicular cancer and multiple myeloma.
In rare cases, twins with identical cellular structure can use cord blood for a perfectly matched transplant.
This type of transplant is rare because it can only be performed in the case of identical twins. Patients with identical siblings share the same tissue. This eliminates the danger of graft-versus-host disease, where donated blood cells start attacking the host’s body. Unlike in autologous transplants, the donated cells will have no trace of disease.
However, there are no immune benefits when using a syngeneic transplant, since both siblings usually have the exact same immune system. This means doctors must use a high amount of chemotherapy and radiation therapy to eliminate cancer cells before attempting a transplant.
Half-matched transplants are also currently being studied for therapy uses. This method requires half of the donated cells to match perfectly, while the other half are mismatched. In theory, this will reduce the chances of graft-versus-host disease, while also boosting the immune system.
Researchers are still working out practical treatment options for transplant patients, and different therapies are discovered every year.
If you are considering cord blood storage to guard your family against certain diseases, find out more about the your banking options here.
Last Updated on February 15, 2017