Leukemia or blood cancer is a cancer of the system’s blood-forming tissues, including the bone marrow and lymphatic system. There are several forms of leukemia; some conditions are common in children, while others primarily develop in adults. Leukemia typically affects the white blood cells, which are the body’s main defense system; they grow and multiply in an orderly way as the body needs them. But in people with leukemia, the bone marrow makes many abnormal white blood cells, which don’t function well. The treatment for leukemia is complex and depends on the type and other factors. Stem cell transplants are one possible treatment option which can lead to a permanent cure. A stem cell transplant alongside chemotherapy or radiation is sometimes provided to treat leukemia, now a days different forms cellular (Cart T) and immunotherapy are also utilized.
What Are Stem Cells?
Blood stem cells are made in the bone marrow, and they are the only cells in the body that have the potential to become any other cell. The stem cells regularly multiply and mature into different types of blood cells, thereby replacing older and worn-out blood ones in the system. Around billions of new blood cells are produced every day. However, if the stem cells cannot make adequate new blood cells, it may result in severe health conditions, including infections, anemia, or bleeding. Healthy stem cells are essential to survive. Cancer and cancer treatments destroy stem cells, where stem cell transplantation (SCT) is the best possible treatment mode.
Stem Cell Transplantation
A stem cell transplant is also referred to as a bone marrow transplant, which involves transplanting stem cells into your body to replace damaged stem cells. Before stem cell transplant, the patient receives chemotherapy and radiation therapy in certain cases to prepare the body for transplantation, and this is known as a conditioning treatment. The stem cells infused into the patient’s bloodstream, travel to the bone marrow and start producing new, healthy blood cells and this process is called engraftment.
Types Of Stem Cell Transplants
· Autologous Stem Cell Transplants:
In this type, stem cells are collected from the patient’s blood or bone, sometimes frozen, and reinfused into blood intravenously after chemotherapy and radiation therapy to destroy cancer cells. This is a simple procedure and is sometimes enough for certain conditions like lymphoma, myeloma etc.
· Allogeneic Stem Cell Transplants:
In this type of transplant, stem cells are taken from a donor or umbilical cord, and these cells are later re-infused into the patient’s blood after receiving chemotherapy or radiation therapy. To assess if a donor’s stem cells are the correct match, the patient will have to get a human leukocyte antigens (HLA) test, where the patient’s blood sample and tissue type with blood samples from a donor are compared.
How Do Stem Cell Transplants Help Treat Leukemia?
Stem cell transplants help to treat leukemia by supporting the body to replace damaged blood cells with healthy ones. The stem cells have the potential to turn into many other types of cells, such as:
Ø Red blood cells supply oxygenated blood to vital organs and tissues
Ø White blood cells, which combat infections
Ø Platelets help with the blood clotting mechanism
When a patient with leukemia receives a stem cell transplant, the system will start producing new blood cells. Combined with high-dose chemotherapy or radiation therapy, this procedure can treat leukemia. Also the donors stem cell will think of the recipient cancer cells as somebody else’s and act against them. This form of immunotherapy is called “Graft vs Leukemia”.
· Allogeneic Stem Cell Treatment
Before getting an allogenic stem cell treatment, patients will have to take pre-transplant treatment, which generally involves chemotherapy, immunotherapy and/or radiation therapy. The main aim of these therapies is to destroy as many cancer cells as possible and to make the recipients body accept the donor stem cells. The donor stem cells are then transferred into the blood stream of the recipient. After a few days, the donor cells will engraft in the new marrow space of the recipient and start making new cells. Additionally, doctors may prescribe certain medications to lessen the risk of graft-versus-host disease (GVHD) a condition where the donated cells can attack the patient’s tissues.
An allogeneic transplant is more advantageous, as the stem cell comes from a healthy donor with no malignant cells. However, it can be hard to find a matching donor; so now a days we can do a half matched transplant (Haplo-identical) from family members.
· Haplo-identical Transplant
This is a rare technically difficult procedure where half matched donors are use. Parents, children or other family members can be taken up as donors and that definitely has advantages. This can either be done using medicines or via a machine called Clinimacs which helps us to eliminate the bad cells and keep the good ones, making the transplant safer.
· Autologous Stem Cell Transplantation
Before autologous stem cell transplantation, the patient will receive medications that make the body produce more stem cells and move stem cells from bone marrow to blood stream. The stem cells will be isolated and frozen until they are required. Then the patient will receive a high dose of chemotherapy and/ or radiation therapy to kill cancer cells. Now patient’s frozen stem cells will be thawed and infused into the patient’s body via a central vein.
Generally, the time taken for the stem cells to start making a constant amount of blood is about 2 to 4 weeks. The patient has to stay in the hospital for several weeks. The doctors will put the patient on various supportive medicines like antibiotics, antiviral or antifungal medications after the procedure to avert the risk of infection.
Once discharged from the hospital, the patient will have to visit the hospital regularly for check-ups and blood work. It will take as long as 6 to 12 months for the blood count to return to normal range.
Consult a healthcare professional to learn more about bone marrow transplantations.
By Dr. Joydeep Chakrabartty, HOD & Sr. Consultant, Dept of Hematology and BMT, HCG Cancer Centre, Kolkata