Usuallu blood cancers are treated with chemotherapy or radiation. However, some cases require bone marrow transplant to cure the cancer. Also termed the hematopoietic stem cell transplant (HSCT), this procedure infuses healthy blood-creating stem cells into the body as a replacement for the bone marrow that is unable to produce enough healthy blood cells.
These transplants are used for replacing non-functioning, diseased bone marrow in leukaemia, sickle cell anaemia, aplastic anaemia and other conditions. The transplant also helps in regenerating the patient’s immune system to fight existing or residual leukaemia and other cancers not destroyed by radiation or chemotherapy.
Bone marrow transplants are of two kinds: autologous and allogeneic. In the autologous form, stem cells are taken from the same person who requires the transplant. In allogeneic, the stem cells are procured from another person, who could either be a matched or unrelated donor. The principle of autologous BMT is the high dose chemotherapy followed by stem cell rescue and this principle is utilized to treat myeloma, lymphoma and solid tumors like neuroblastoma, germ cell tumors, ewing’s sarcoma, etc. the other principle is to reset the immune system to treat auto-immune diseases like Multiple Sclerosis, Maysthenia, CIDP, NMO, Systemic Sclerosis, and others.
The principle of allogenic BMT is to correct the deficient blood component like Thalassemia, sickle cell disease, aplastic anemia, inborn errors of metabolism etc. The other principle is to provide new immune system to fight against the blood cancers.
Reviewing the Risks
A bone marrow transplant may have several risks. While some experience limited problems with bone marrow transplants, others could face severe complications requiring treatment and hospitalisation. Occasionally, these may be life-threatening. The risks vary due to multiple factors such as the type of transplant, the disease/condition that necessitates the transplant, the person’s age and overall health.
The possible complications may include graft-versus-host disease (only in allogeneic transplant), stem cell or graft failure, infections, organ damage, infertility, cataracts, new cancers and even death. The patient and physician must have a thorough discussion to weigh the risks and benefits before opting for the procedure.
The risk of graft-versus-host disease (GVHD) in allogeneic transplants must also be considered. In this case, the donor stem cells comprising the new immune system perceive the patient’s organs and body tissues as foreign elements and attack them. GVHD could occur at any time after the transplant. The risk is higher if the stem cells are derived from an unrelated donor.
GVHD can be either acute or chronic. Typically, acute GVHD occurs in the first few months after the transplant and affects the skin, liver or digestive tract. Chronic GVHD generally develops later and may affect multiple organs.
How to Prepare
A series of pre-transplant tests and procedures will be undertaken to assess the patient’s overall health and general condition. These procedures also ascertain that the person is physically prepared for the transplant. The evaluation could take place over several days.
A long, thin tube or intravenous catheter will be implanted into a large vein in the patient’s neck or chest. Also called a central line, the catheter is in place during the entire treatment. The central line is used by the transplant team to infuse transplanted stem cells, blood products and medications into the patient’s body.
The Autologous Transplant
If an autologous transplant is done, the patient undergoes a procedure termed apheresis that collects blood stem cells. Before this is done, the person will receive growth factor injections daily to boost stem cell production and shift stem cells into his/her circulating blood so these can be collected.
In apheresis, blood drawn from a vein is circulated via a machine. This machine segregates the blood into different parts, which include stem cells. These cells are then collected and frozen for later use in the transplant. The blood that remains is returned to the patient’s body.
The Allogeneic Transplant
In allogeneic transplants, donors provide the stem cells that come from their blood or bone marrow. As per the patient’s situation, the transplant team decides which is better. Another kind of allogeneic transplant sources stem cells from the umbilical cord blood. Therefore, it is also referred to as cord blood transplant. Mothers may donate umbilical cords after their babies are born. This cord blood is frozen and stored in a cord blood bank to be used later when needed for a bone marrow transplant.
The Process of Conditioning
Once the pre-transplant procedures are over, the patient undergoes a process called conditioning. During this process, the patient undergoes chemotherapy and radiation, if required. This seeks to destroy cancer cells if the person is under treatment for cancer that could spread to other regions of the body, or to suppress his/her immune system and have the bone marrow prepared for the new stem cells.
The kind of conditioning process given depends on varied factors such as the ailment being treated, the patient’s general health and the kind of transplant planned. The patient could be given both chemotherapy and radiation. Or either one of these treatments as part of the conditioning process.
This process could include side effects like hair loss, diarrhoea, nausea and vomiting, mouth sores or ulcers, bleeding, infection, infertility or sterility, anaemia, fatigue, cataracts and organ complications, e.g., heart, lung or liver failure. The patient may be prescribed medications or other measures that can reduce these side effects.
The Post-conditioning Period
After the conditioning process is completed, a bone marrow transplant can be done. On the day of the transplant, stem cells will be infused into the patient’s body via the central line. As the transplant infusion is painless, the patient will remain conscious during the entire procedure.
Once the new stem cells enter the patient’s body, they travel through his/her blood to the bone marrow. Sometime later, they will multiply and begin to produce new healthy blood cells. Termed engraftment, this process may require several weeks or more before the percentage of blood cells in the body begins reaching the normal range.
Post-transplant Precautions
In the days and weeks following the bone marrow transplant, blood and other tests will be done to monitor the patient’s condition. Medications may be needed to manage nausea, diarrhoea and other complications. After the bone marrow transplant, one is kept under close medical supervision. If the patient has infections or other complications, a longer hospital stay will be advised. Taking the type of transplant and the threat of complications into consideration, the patient may need to stay close to the hospital for weeks or months to facilitate close monitoring.
Periodic transfusions of platelets and red blood cells may be necessary until the patient’s bone marrow begins to produce adequate amounts of cells by itself. The patient could continue to remain at a higher risk of infections or allied complications for months or years after the transplant. Additionally, one will need to meet the healthcare team for the rest of his/her life to check for late complications.
After the treatment, since the immune system needs time to recover, medications may be prescribed to prevent infections. Regular physical activity is also recommended to control weight, strengthen muscles and bones, boost endurance and keep the heart healthy.
A bone marrow transplant could cure some ailments and put others into remission. However, steps to prevent cancer are all the more important in the post-transplant phase. Besides abstinence from smoking, regular cancer screenings are advisable. In many cases, a bone marrow transplant could help in extending a person’s life and improving the quality of life too.