Stem cell transplants are often used to treat multiple myeloma. This type of treatment has been effective over the past several decades.
Stem cells are immature cells that act as factories for making the fully developed cells that have specialized roles in the body. There are many types of stem cells, each of which creates different fully formed cells.
Hematopoietic stem cells (HSCs) are a type of stem cell that produces blood cells. These cells continuously make new blood cells throughout a person’s life. The new blood cells are needed to replace old or damaged blood cells that can no longer work properly. HSCs can make all types of blood cells, including:
HSCs are primarily found in the bone marrow — the soft tissue found inside certain bones. Some of these stem cells can also be found in the peripheral blood (the blood inside of blood vessels that flows throughout the body). Blood from the umbilical cord of newborn babies also contains many HSCs.
A stem cell transplant (SCT) is a procedure sometimes used to treat types of blood cancer. During stem cell transplantation, a person receives aggressive cancer treatments that kill old blood cells. Their old HSCs are replaced with new, healthy HSCs. Previously, stem cell transplants were called bone marrow transplants, but this term is not used as often anymore.
There are a couple of reasons why an SCT can fight cancer. First, it allows a person with myeloma to undergo stronger treatments than would normally be possible. High doses of chemotherapy or radiation will kill not only cancer cells but also healthy blood cells and HSCs. Transplanting new stem cells after aggressive treatments allows the body to rebuild its blood cells. There is an additional benefit for SCTs that use cells from a donor (another person). Myeloma cells often evade the body’s immune system. However, immune cells from a donor are often better at attacking cancer cells.
Not everyone with myeloma is eligible to undergo a stem cell transplant. This treatment can cause many side effects, so it may not be a good fit for someone who is older or who has other serious health problems.
Stem cell transplantation may work differently depending on where and who the new stem cells come from.
In an autologous stem cell transplant, the new HSCs come from a person's own body. The stem cells are removed before high-dose treatment and then put back into the person's body. The HSCs travel to the bone marrow and begin making new, healthy blood cells to replace the ones that were lost.
People with multiple myeloma most often receive autologous transplants. In some cases, those with myeloma receive a tandem transplant, in which two autologous transplants are given in a row. However, tandem transplants are often only used for people with high-risk myeloma or in cases where the first transplant did not work.
Allogeneic stem cell transplants use new stem cells from a donor. HSCs for allogeneic transplants can come from any of the three places where stem cells are found: the bone marrow, peripheral blood (called a peripheral blood stem cell transplant), or umbilical cord blood (called a cord blood transplant).
Allogeneic transplants have one major drawback and one potential benefit when compared with autologous transplants. If the donated stem cells contain substantially different types of proteins than the recipient’s cells, the recipient may suffer a serious immune system reaction called graft-versus-host disease (GVHD). A person’s risk of developing GVHD is decreased if a close match is found. The advantage of allogeneic transplants is that donated immune cells may help attack cancer cells. This is sometimes called a graft-versus-cancer or graft-versus-myeloma effect.
In the past, allogeneic transplants were rarely recommended for people with multiple myeloma because of their severe and sometimes fatal side effects. However, researchers are studying new transplant regimens and improving treatment options for side effects. These may make allogeneic transplants safer. Although allogeneic transplants aren’t part of the usual standard of care for people with myeloma, they are sometimes used in clinical trials.
Identical twins have very closely matched immune cells. When an allogeneic transplant is performed between two identical twins, it is called a syngeneic transplant. This type of transplant won’t cause GVHD, but it may also not be as effective at killing cancer cells.
If a matched donor cannot be found, doctors may sometimes recommend a transplant using cells from a close relative (a child, parent, or sibling). A relative’s HSCs are often not a perfect match, but they may still be useful for a transplant. This type of transplant may be called a haplotype mismatched or a half-match transplant.
Sometimes, people who are older or in poor health can’t withstand the side effects of high-dose chemotherapy or radiation. A reduced-intensity transplantation uses less aggressive treatments. Reduced-intensity transplants are used along with allogeneic transplants and may also be called mini transplants or nonmyeloablative transplants.
Stem cell transplantation is a long process. It involves three main phases: preparation; chemotherapy, radiation therapy, or a combination; and stem cell infusion. The procedure is followed by a long recovery period.
Not everyone is a good candidate for transplantation. Doctors will run several tests to determine whether this procedure is a good fit for you. These may include various blood tests, imaging studies, and tests to see how well your organs are working.
Preparation for an autologous transplant involves collecting your HSCs. To accomplish this, your doctor will give you growth factors. These substances encourage stem cells to make more copies of themselves and travel from the bone marrow to the peripheral blood. This raises the overall number of stem cells in your blood. A machine then collects your blood, removes the stem cells, and returns the rest of the blood to your body. This process, called apheresis, takes three to four hours and often needs to be repeated for up to five days.
Allogeneic transplantation is only possible if doctors can find a good donor. Doctors use laboratory tests to determine whether a donor’s cells match yours. Your doctors may test family members to see if they are good matches, or they may look through a registry of potential donors. If your health care team finds a suitable donor, they may collect stem cells using the same procedures used for an autologous transplant. Alternatively, doctors may perform a surgical procedure to remove HSCs from the bone marrow.
Before receiving new HSCs, you need to go through aggressive cancer treatments. This may be called conditioning treatment.
Conditioning treatment usually consists of high doses of Alkeran (melphalan), a chemotherapy drug. You receive chemotherapy through a catheter (small tube placed into your chest). These treatments destroy most of your myeloma cells and make more room for new stem cells in the bone marrow. In the case of an allogeneic transplant, conditioning also weakens the immune system, preventing it from attacking the new donor cells. Conditioning treatment may take one to two weeks.
Once chemotherapy treatments are complete, you will receive the new stem cells. Doctors deliver cells by infusing them through your catheter. You may need multiple stem cell infusions. Each infusion typically takes less than one hour.
You will need to stay in the hospital as you recover from your transplant. You may not be able to go home until you have met certain criteria, such as not having a fever for a certain number of days or having any side effects under control.
As you recover, your doctor will perform tests to determine whether the transplant worked. This includes blood tests to count the numbers of each blood cell type. Aggressive conditioning treatments lower the number of healthy blood cells. If your transplant was successful, your new stem cells will engraft (make new blood cells). It often takes two to six weeks for blood counts to return to normal. Additionally, other tests may show that the number of cancer cells is decreasing.
Transplants decrease your levels of healthy blood cells, including immune cells, so you will be at risk for infections as you recover. You may need to take antibacterial, antiviral, and antifungal medications. You will also have reduced numbers of red blood cells and platelets. You may need to get blood transfusions if your blood cell counts are too low.
Once you go home from the hospital, you will continue to need regular follow-up visits and tests to make sure you are recovering properly. It may take a year or more before your blood cells are working normally again. Your doctor may tell you not to participate in any activities for three to six months after stem cell transplantation.
Transplantation can cause side effects at each stage of the process. The process of collecting HSCs may cause mild dizziness, tingling in the hands or feet, chills, shaking, and muscle cramps.
Aggressive chemotherapy can also cause side effects. Chemotherapy may lead to pain, tiredness, nausea, vomiting, diarrhea or constipation, mouth sores, hair loss, or trouble thinking clearly. Common side effects of radiation therapy include tiredness, skin problems, headache, nausea, vomiting, and diarrhea. These side effects often go away after the treatment is completed, although chemotherapy and radiation therapy can also cause long-term health problems.
Short-term side effects of an SCT include:
Sometimes, stem cell transplants cause longer-lasting problems. These may include:
As you are considering whether to undergo a stem cell transplant, talk to your doctor about what side effects to expect. After you have an SCT, tell your health care team about any health problems you are experiencing. They can help you learn how to manage short- or long-term complications.
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