Stem cell transplantation (SCT) offers many people with blood and bone marrow cancers hope for a potential cure. More than 17,500 stem cell transplants are performed in the U.S. annually.
MyLeukemiaTeam sat down with Dr. Matt Kalaycio to better understand stem cell transplantations as a treatment for leukemia. Dr. Kalaycio is the former chair of the department of hematology and medical oncology at the Cleveland Clinic Taussig Center Cancer Institute. An expert in blood cancers, Dr. Kalaycio is currently a professor in the Cleveland Clinic Lerner College of Medicine at Case Western Reserve University.
“The treatment of cancer in general, and blood cancers in particular, is complex,” Dr. Kalaycio said. “It can even be difficult for specialist medical practitioners to keep up with the rapidly evolving treatment landscape." With improvements in procedures and recovery, SCT has become safer. Post-transplantation survival rates also continue to improve.
Stem cells can be thought of as the building blocks of the human body. They are a unique category of cells that can develop into different, specialized types of cells. Hematopoietic stem cells (HSC), or blood-forming stem cells, are made in a person’s bone marrow.
Blood-forming stem cells can develop into three main types of blood cells that all humans need to be healthy:
HSCs are located in several parts of the body:
During SCT, healthy stem cells are introduced to replace existing bone marrow and essentially create a new immune system. SCT is sometimes referred to as a bone marrow transplant (BMT). A blood, or hematopoietic, stem cell transplant (HSCT), is used to treat some forms of leukemia.
During the SCT procedure, healthy blood stem cells are introduced into a vein and then travel to a person’s bone marrow. Here, they multiply, forming new stem cells that develop into healthy blood cells. These hematopoietic stem cells regenerate a person’s blood and immune cells, enabling them to kill cancer cells and potentially cure a person of leukemia.
The blood-forming stem cells for an HSCT can either be sourced from one’s own body (autologous) or from someone else, a donor (allogeneic).
Autologous stem cell transplants (AUTO) utilize a person’s own stem cells to regenerate bone marrow and blood cells. “An autologous transplant is just a mechanism to give more chemotherapy,” explained Dr. Kalaycio. A person’s hematopoietic stem cells are collected and then injected back into them after chemotherapy has been given.
When donor stem cells are collected from another person, it is known as an allogeneic stem cell transplant (ALLO). ALLO is the type of transplant more often used to treat blood cancers such as leukemia. Donor cells are preferable for leukemia treatment because of the graft-versus-leukemia effect. The GVL effect occurs when the donor cells recognize and kill any remaining leukemia cells. GVL is unique to ALLO SCTs, and does not occur with autologous transplants.
A reduced-intensity allogeneic transplant is a less aggressive standard ALLO. Specifically, the person’s own stem cells aren’t entirely wiped out. Reduced-intensity ALLO treatments are used in some older or sicker people who could not otherwise tolerate a full-intensity transplant.
In a syngeneic SCT, the stem cell donor is the recipient’s identical twin. The upside of an identical twin donor is that there is no risk of a person’s body rejecting the graft because they have the same genes. The downside is that the stem cells don’t have as much antileukemic impact.
Stem cell transplantation can be used to treat certain neoplastic blood diseases (blood cancers), including leukemia. Not every treatment works 100 percent of the time for every person. SCT is not suitable for all types of leukemia.
The most common form of leukemia in adults under 25 years old and children is acute lymphoblastic leukemia (ALL). ALL involves lymphocytic cells in early stages of development. Stem cell transplantation is not used as the first or primary treatment for ALL. HSCT may be used as a treatment for people with ALL who are considered high risk, or when a person’s ALL doesn’t respond well to other treatments.
Acute myeloid leukemia (AML) involves myeloid cells in early stages of development. AML is the most common form of acute leukemia found in adults. AML is also known as acute myelogenous leukemia, acute myelocytic leukemia, acute granulocytic leukemia, and acute non-lymphocytic leukemia. SCT may be a recommended treatment for people with AML, depending on whether their leukemia is classified as favorable, intermediate, or high risk.
Donor suitability is one of the most important criteria in determining whether or not HSCT is a potential treatment option for a person with leukemia.
A person’s tissue type is determined by a set of proteins (markers) called human leukocyte antigens (HLAs). HLAs are found on the surface of most cells. HLA proteins are responsible for telling the immune system whether a cell belongs to you or is a foreign, invading cell. There are several HLA markers.
Donor matching is determined by the tissue type similarities between the donor and the recipient. How closely the HLA cells match between the donor and recipient is one of the most important determining factors of an SCT’s success.
A close family member or relative is typically more likely to be a close HLA match than an unrelated person. Because a person inherits half of their HLA markers from each parent, biological siblings have a 1 in 4 chance of having the same HLA type. Only 25 percent to 35 percent of people have a sibling who is an HLA match.
Because there are far more options available, a person’s chance of finding a good match in an unrelated donor is higher than having a matched family member. The less closely matched, the higher the risk of complications and graft failure. For urgently needed SCTs, umbilical cord blood and haploidentical (half match) transplantation are often required, and sometimes preferred.
HSCT isn’t for every case of leukemia or even for every person with the types of leukemia for which the procedure is approved. HSCT is a complex, lengthy, and demanding medical procedure. “The usual recommendations for anybody, whether or not they're getting a stem cell transplant, are to stop smoking, exercise, and get more sleep,” Dr. Kalaycio said. “Take care of yourself.”
A person needs to be as strong as possible before starting the transplantation process. Your treatment team will run several tests to ensure that you are eligible. If you’re undergoing ALLO transplantation, a donor will need to be identified and matched. In both AUTO and ALLO, stem cells are harvested in preparation for the procedure. “Going to transplant usually requires being in remission, or at least responding to whatever treatment a person is currently getting,” Dr. Kalaycio said.
The aim of conditioning treatment is to kill any remaining leukemia cells and weaken a person’s immune system to reduce the risk that the graft will be rejected. To achieve this, high doses of chemotherapy treatments and sometimes full-body radiation occur in the week right before the stem cells are infused into the recipient. “Staying with the program prior to transplant is extremely important,” said Dr. Kalaycio. Strict treatment adherence is vital to the success of the SCT.
The conditioning treatment is adjusted from person to person. Very intense treatment is called myeloablative, less intense treatment is known as non-myeloablative, or reduced intensity, chemotherapy.
“I had three rounds of chemo,” said one MyLeukemiaTeam member about his SCT experience. “I stayed in the hospital the whole month of October. I went back in the day after Thanksgiving for a week for another chemotherapy treatment, then went back in January for chemo and the transplant. It took three weeks.”
Stem cell infusion involves the donor cells (or in AUTO transplants, the recipient’s own cells) being intravenously infused into the body. This part of the transplantation process usually takes 30 minutes to an hour. It’s a painless process and doesn’t require the person to be anesthetized.
Recovering from an STC procedure varies from person to person, but in most instances, the recovery process following a stem cell transplant takes time.
After the transplant, a hospital stay of at least a few weeks is necessary. “The first 100 days after a stem cell transplant are so crucial,” Dr. Kalaycio said. “It takes a good 100 days from infusion to really get settled in and to do what it needs to.” The infused blood has to settle into your bone marrow and begin to produce new blood cells, which is referred to as engraftment. “The 100-day rule really doesn't apply to autologous transplants” because of the reduced risk of graft rejection, Dr. Kalaycio noted.
During this critical window, the treatment team will check blood cell counts frequently. If and when engraftment occurs, the white blood cell, red blood cell, and platelet counts will rise. When neutrophils recover, hospitalization is usually no longer necessary.
“After the first 100 days, the donor's immune system will have had a chance to take hold,” Dr. Kalaycio said. There will be a lot of medications (such as immunosuppressants and antibiotics), appointments, and tests to ensure that the transplanted cells have the best chances of success. There are also side effects from the conditioning treatment and the transplantation to manage.
“I am fine now, almost 200 days post-transplant,” shared a MyLeukemiaTeam member with AML. “My cancer is in remission! I have another bone marrow biopsy this week — it’s an important one, telling me where I am.”
The closer the donor-recipient match, also known as the immunological compatibility, the lower the risk of complications after the SCT. As with all cancer treatments, there are risks and potential side effects and complications when undergoing an SCT. Some side effects are temporary, while others can be long-lasting to permanent. Side effects and complications can vary from mild to life-threatening.
Graft-versus-host disease (GVHD) is a condition in which donated stem cells (the graft) attack the recipient’s cells (the host). GVHD is potentially serious, and in some cases, life-threatening. There are two types of GVHD: acute and chronic, and each type of GVHD has different signs and symptoms. It's possible for someone to develop one or both types of GVHD. They may develop one after the other, or both may occur concurrently.
Conditioning treatment can weaken a person’s immune system. “Folks who have had treatment for leukemia or a stem cell transplant are at far greater risk for the consequences of an infection,” Dr. Kalaycio said. “Most of the infections that we deal with come from within, not from without, so the infections that the patients are most likely to get are probably already in them, and are not going to be obtained from the environment.”
One potential infection can potentially be acquired from miso soup. “Aspergillus spores and cultures help make miso soup, the opening course often available in Japanese restaurants,” Dr. Kalaycio said. To avoid any unnecessary risk, a person undergoing SCT should avoid miso soup until medically cleared.
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