Types of stem cell and bone marrow transplants (2023)

Stem cell transplants are used to return stem cells when the bone marrow has been destroyed by disease, chemotherapy (chemotherapy) or radiation. Depending on where the stem cells come from, the transplant procedure can be described as follows:

• Bone marrow transplant (BMT)
• Peripheral blood stem cell transplantation
• umbilical cord blood transplant

All of them can be referred to as hematopoietic stem cell transplants.

A typical stem cell transplant for cancer uses very large doses ofchemotherapyare used, sometimes together withradiotherapy, to try to kill all the cancer cells. This treatment also kills stem cells in the bone marrow. this is calledmyeloablationormyeloablative therapy. Soon after treatment, stem cells are given (transplanted) to replace those that have been destroyed. The replacement stem cells are given into a vein, similar to a blood transfusion. The goal is for the transplanted cells to settle in the bone marrow over time, begin to grow and form healthy blood cells. This process is calledimplantation.

There are 2 main types of transplants. They are named after the stem cell donor.

• Autolog:car meansauto. The stem cells in autologous transplants come from the same person who receives the transplant, so the patient is his or her own donor.
• Halogen:halo meansOthers. The stem cells in allografts come from someone other than the patient, whether a matched donor or not.

Autologous stem cell transplant

In this type of transplant, the first step is to remove orharvesttheir own stem cells. Your stem cells are taken from your bone marrow or blood and then frozen. (You can learn more about this process atWhat is it like to donate stem cells?) After you receive high doses of chemotherapy and/or radiation as part of your myeloablative therapy, the stem cells are thawed and returned to you.

Benefits of autologous stem cell transplantation:One benefit of autologous stem cell transplantation is that you get your own cells back. If you take With your own stem cells back, you don't have to worry about them (called transplanted or "engrafted" cells) being rejected by your body.

scratchs of autologous stem cell transplantation:Transplants can still fail, which means that the transplanted stem cells will not reach the bone marrow and produce blood cells as they should. Furthermore, autologous transplants cannot produce the "graft versus cancer" effect. A potential downside of an autologous transplant is that cancer cells can be collected along with the stem cells and later reintroduced into your body. Another disadvantage is that your immune system is the same as before the transplant. This means that the cancer cells were able to escape an attack by your immune system and may be able to do so again.

This type of transplant is mainly used to treat certain medical conditions.leukemias,lymphoma, Emultiple myeloma. It is sometimes used for other types of cancer, such astesticular cancerENeuroblastomaand certain types of cancer in children. Doctors may also use autografts for other diseases, such as systemic sclerosis, multiple sclerosis (MS), and systemic lupus erythematosus (lupus).

Elimination of cancer cells in stem cells saved for autologous transplants

To prevent the remaining cancer cells from being transplanted along with the stem cells, some centers treat the stem cells before returning them to the patient. This can be calledLavar. While this may work for some patients, there haven't been enough studies yet to know if this is actually a benefit. A possible downside to purification is that some normal stem cells may be lost during this process. This can mean that your body takes longer to start producing normal blood cells and you may have very low and unsafe levels of white blood cells or platelets for an extended period of time. This can increase the riskinfectionsor bleeding problems.

Another treatment to kill cancer cells that may be in the returned stem cells is to administer anti-cancer drugs after the transplant. Stem cells are not treated. After the transplant, the patient is given anticancer drugs to get rid of any cancer cells that may be in the body. this is calledliveLavar. For example lenalidomide (Revlimid^®) can be used in this way in multiple myeloma. The need to remove cancer cells from transplanted stem cells or from transplant patients, and how best to do this, remains to be explored.

Tandem transplants (double autologous)

Performing 2 autologous transplants in a row is calledTandemtransplantationor onedouble autologous transplant.In this type of transplant, the patient receives 2 high-dose chemocycles as myeloablative therapy, each followed by a transplant of their own stem cells. All the necessary stem cells are collected before the first high-dose chemotherapy treatment and half are used for each transplant. Typically, the 2 cycles of chemotherapy are given within 6 months. The second is given after the patient has recovered from the first.

Tandem transplants have become the standard of care for certain types of cancer. High-risk types of childhood neuroblastoma and multiple myeloma in adults are cancers for which tandem transplants seem to show good results. But doctors don't always agree that these are actually better than a single transplant for certain types of cancer. As this treatment includes 2 transplants, the risk of serious consequences is greater than with a single transplant.

An autologous transplant followed by an allogeneic transplant is sometimes called a tandem transplant. (See minitransplants below.)

Allogeneic stem cell transplantation

Allogeneic stem cell transplants use stem cells from donors. In the most common type of allogeneic transplant, the stem cells come from a donor whose tissue type is very similar to yours. (This is discussed in Matching Patients and Donors.) The best donor is a close family member, usually a brother or sister. If you don't have a good family match, a public donor can be found through a national registry. This is sometimes calledDIRT(matched unrelated donor)Transplantation. Transplants with a MUD are generally more risky than those with a matched relative.

An allogeneic transplant works in the same way as an autologous transplant. Stem cells are collected from the donor and stored or frozen. After receiving high doses of chemotherapy and/or radiation as myeloablative therapy, the donor stem cells are thawed and given to you.

Blood taken from the placenta and umbilical cord of newborns is a type of allograft. This small volume ofCabobloodit has a high number of stem cells that tend to multiply quickly. Cord blood transplants are performed for both adults and children. As of 2017, approximately 700,000 units (batches) of cord blood have been donated for public use. And even more were collected for private use. In some studies, the risk of a cancer not going away or coming back after a cord blood transplant was lower than after a transplant from an unrelated donor.

Benefits of allogeneic stem cell transplantation:Donor stem cells make their own immune cells that can help kill any cancer cells that remain after high-dose treatment. This is calledGraft versus CancerorGraft versus Tumor It is made. Other benefits include that the donor can often be asked to donate more stem cells or even white blood cells if needed, and stem cells from healthy donors are cancer free.

scratchs of allogeneic stem cell transplantation: Transplantation or transplantation may not take place - which means that the transplanted donor stem cells may die or be destroyed by the patient's body before settling in the bone marrow. Another risk is that the donor's immune cells will not only attack the cancer cells, but also the healthy cells in the patient's body. this is calledGraft versus host disease. There is also a very low risk of certain infections from the donor's cells, although donors are tested before donating. You are more at risk for infections that you once had that your immune system was keeping in check. These infections can occur after an allogeneic transplant because your immune system is kept in check (suppressed) by drugs called drugsimmunosuppressant drugs. Such infections can cause serious problems and even death.

An allogeneic transplant is most commonly used to treat certain types ofleukemia,lymphoma,multiple myeloma,myelodysplasty syndromeand other bone marrow diseases such as aplastic anemia.

Mini-Transplantes (transplantes non-mieloablativos)

For some people, due to age or certain medical conditions, it is riskier to have myeloablative therapy, which obliterates all of the bone marrow before a transplant. For these people, doctors may use a type of allograft, sometimes called a mini-graft. Your doctor may refer to it as anon-myeloablative transplantor mentionReduced Intensity Conditioning (RIC). Patients who receive a mini-graft generally receive lower doses of chemotherapy and/or radiation than standard myeloablative transplantation. The purpose of the mini-transplant is to kill some of the cancer cells (which will also kill some of the bone marrow) and to suppress the immune system just enough for the donor stem cells to colonize the bone marrow.

Unlike the usual allogeneic transplant, after a mini-transplant, the donor and patient's cells coexist in the patient's body for some time. But slowly, over months, the donor cells take over the bone marrow and replace the patient's own bone marrow cells. These new cells can then mount an immune response against the cancer and help kill the patient's cancer cells - the graft-versus-cancer effect.

An advantage of a mini-transplant is that it requires lower doses of chemotherapy and/or radiation. And because not all stem cells are killed, the blood cell count doesn't drop as much while you wait for the new stem cells to start forming normal blood cells. This makes it especially useful for elderly patients and people with other health conditions. Rarely, it can be used in patients who have already had a transplant.

Mini-grafts treat some conditions better than others. They may not work well for patients with a lot of cancer in their bodies or people with fast-growing cancers. Although chemotherapy and radiation have fewer side effects than standard allogeneic transplantation, the risk of graft-versus-host disease is the same. Some studies have shown that, for some types of cancer and other blood disorders, adults and children can get the same results with a mini-transplant as with a standard transplant.

Syngeneic stem cell transplants (for identical siblings)

This is a special type of allograft that can only be used if the patient has an identical sibling (twins or triplets) - someone who has the exact same type of tissue. An advantage of syngeneic stem cell transplantation is that graft-versus-host disease is not a problem. Furthermore, there are no cancer cells in the transplanted stem cells, as could be the case with an autologous transplant.

One disadvantage is that there is no graft versus cancer effect because the new immune system is very similar to the recipient's immune system. Every effort must be made to destroy all cancer cells before the transplant is done to prevent the cancer from returning.

Transplanted Halbgepaarte

Improvements were made to use family members as donors. This type of transplant is called Ahalf-match (haploidêntico) transplant for those who do not have a fully compatible or identical family member. This may be another option to consider along with cord blood transplantation and matched unrelated donor (MUD) transplantation.

The importance of patient-donor compatibility

Whenever possible, it is very important that the donor and recipient avoid a close tissue match. transplant rejection.Transplant rejection occurs when the recipient's immune system recognizes the donor's cells as foreign and tries to destroy them like bacteria or viruses. Transplant rejection can lead to transplant failure, but it is rare when the donor and recipient are a match.

A more common problem is that when donated stem cells create their own immune cells, the new cells can mistake the patient's cells for foreign and attack their new "home." this is calledGraft versus host disease. (VerStem cell transplant side effectsmore about that). The new transplanted stem cells attack the body of the person who received the transplant. This is another reason why finding the closest possible match is so important.

What makes a stem cell donor compatible? What does it mean to be an HLA Match?

Many factors play a role in how the immune system recognizes the difference between self and non-self, but most important for transplants is theHuman Leukocyte Antigen (HLA)System. Human leukocyte antigens are proteins found on the surface of most cells. They form a person's tissue group, which is distinct from a person's blood group.

Each person has a set of HLA antigen pairs. We inherit it from our parents and, in turn, we pass it on to our children. Doctors try to match these antigens when they find a donor for a person who is going to have a stem cell transplant.

Matching the donor and recipient HLA tissue types plays an important role in the functioning of the transplant. A match is best when all 6 major known HLA antigens are the same - a 6 out of 6 match. People with these matches have a lower risk of graft-versus-host disease, transplant rejection, weak immune systems and serious infections . Bone marrow and peripheral blood stem cell transplants sometimes use a donor with a single mismatched antigen - a 5 out of 6 match. In cord blood transplants, a perfect HLA match does not seem to matter much, and even a sample with some incompatible antigens may be ok.

Doctors are learning more and more about the best ways to match donors. Today, siblings may need fewer tests because their cells vary less than an unrelated donor. However, to reduce the risk of type mismatches between unrelated donors, more than the 6 basic HLA antigens can be tested. For example, doctors sometimes try to get a 10 out of 10 match. Certain transplant centers now require high-resolution matching, which drills down into tissue types and allows for more specific HLA matching.

find a match

There are thousands of different combinations of possible HLA tissue types. This can make finding an exact match difficult. HLA antigens are inherited from both parents. When possible, the search for a donor usually begins with the patient's siblings (siblings) who have the same parents as the patient. There is a 1 in 4 chance that one of the siblings will be a perfect match (that is, you both received the same set of HLA antigens as your parents).

If a sibling is not a good match, the search may shift to relatives less likely to be a match - parents, half-siblings, and relatives such as aunts, uncles, or cousins. (Spouses are no more likely to be a good match than other people who are not related.) If no close relatives are found, the transplant team expands the search to the general public.

As unlikely as it sounds, it is possible to find a good match with a stranger. To assist in this process, the team will use transplant registries such as those listed here. The registries serve as matchmakers between patients and voluntary donors. You can search and access millions of potential donors and hundreds of thousands of cord blood units.

be the game (sooner orNational Bone Marrow Donor Program)
Toll Free Number: 1-800-MARROW-2 (1-800-627-7692)
Internet site:www.bethematch.org

Blood and Bone Marrow Transplant Information Network
Toll free number: 1-888-597-7674
Internet site:www.bmtinfonet.org

Various other international registries are also available, depending on an individual's tissue type. Sometimes the best matches are found among people of similar racial or ethnic background. Compared to other ethnic groups, whites are more likely to find a perfect match for a stem cell transplant from unrelated donors. This is because ethnic groups have different HLA types and historically there has been less diversity in donor registries or fewer non-white donors. However, the chances of finding a matching donor increase each year as more volunteers find out and apply to the registries.

Finding an unrelated donor can take months, although cord blood can go a little faster. A single game can require searching millions of records. As transplant centers use high-resolution tests more frequently, matching becomes more complex. 10 out of 10 perfect matches in this level are much harder to find. But transplant teams are also getting better at figuring out which types of mismatches can be tolerated in which situations—that is, which mismatched antigens are least likely to affect transplant success and survival.

Keep in mind that this process has steps - there could be multiple matches that look promising but don't work out as expected. The team and registry will continue to look for the best possible match for you. If your team finds an adult donor through a transplant registry, the registry will contact the donor to determine final testing and donation. If your team finds matching cord blood, the registry will send the cord blood to the transplant center.