Bone Marrow or Stem Cell Transplant Treatments
In a peripheral blood stem cell transplant — also called bone marrow transplant — a patient’s blood-forming stem cells are replaced by infusing new ones into his or her bloodstream. This treatment can be a cure for certain forms of blood cancer, for example, acute myeloid and lymphoblastic leukaemia, chronic myeloid and lymphocytic leukaemia, myelodysplasia, non Hodgkin lymphoma, Hodgkin lymphoma, multiple myeloma and myelofibrosis.
Transplant patients must not only have access to the expertise of all transplant team members, and to transplant nursing and supportive services, but to the leading-edge methods developed through collaborative efforts between clinicians and research staff in the laboratories.
The physicians offer each patient the transplantation approach most likely to result in a cure or improve survival. When there is a good chance for improved outcome, the doctors may suggest that a patient participate in a clinical trial.
What are Stem Cells and where are they found?
Blood-forming or haematopoietic stem cells are immature cells that can develop into any type of blood cells, including:
Before a transplant, stem cells can be collected from a person’s bone marrow or from the bloodstream, where peripheral blood stem cells (PBSC) circulate.
Another source of stem cells is blood from a newborn baby’s umbilical cord.
What are the types of Transplant?
There are two main types of transplant: autologous, in which a patient’s own stem cells are collected and then transplanted back into the patient, and allogeneic transplant, in which the stem cells are obtained from a donor other than the patient. In allogeneic transplant the donor usually needs to be a full tissue match – this can either be a brother / sister or a matched unrelated volunteer donor. Tissue matching is performed on a blood sample from the patient and potential donors. High resolution tissue typing using DNA technology is essential when searching for an unrelated donor. When a matched unrelated donor cannot be identified, cord blood stem cells or half-matched (haplo-identical) family donors can be used.
Who might benefit from bone marrow / stem cell transplantation?
Here are some of the most common diseases treated with autologous or allogeneic transplantation:
|Acute Myeloid Leukaemia||Allogeneic|
|Acute Lymphoblastic Leukaemia||Allogeneic|
|Non-Hodgkin Lymphoma||Autologous or Allogeneic|
|Hodgkin Lymphoma||Autologous or Allogeneic|
|Multiple Myeloma||Autologous or Allogeneic|
|Chronic Myeloid Leukaemia||Allogeneic|
|Chronic Lymphocytic Leukaemia||Allogeneic|
What is the basic procedure for Peripheral Blood Stem Cell or Bone Marrow Transplantation?
Before an autologous or allogeneic transplant, either chemotherapy or a combination of chemotherapy and radiation is given to the patient. This treatment is called the preparative or conditioning regimen, is designed to eradicate cancerous cells as well as the blood-forming stem cells in the bone marrow, causing a fall in the patient’s blood count and immunity.
Next, peripheral blood stem cells or bone marrow stem cells are infused into the patient’s bloodstream through an intravenous catheter, in a procedure that is similar to a blood transfusion. No surgery is required. Over the following days, the transplanted stem cells travel to the bone marrow, where they will grow and develop into new mature blood cells, including red and white blood cells and platelets.
During the early few days following transplant when the blood counts are low, special precautions are taken to protect the patient from infection and bleeding.
Successful transplants provide patients with a new, healthy bone marrow with a return to normal blood counts and immunity. Allogeneic transplants also give patients a new immune system, which is derived from the donor’s stem cells and this may help prevent recurrence of the leukaemia or lymphoma.
What is Pre-transplant treatment or Conditioning Regimen ?
In some patients this pre-transplant treatment is given in high doses to try and destroy all the abnormal leukaemia or lymphoma cells remaining in the patient. This intensive treatment in the form of chemotherapy alone or chemotherapy and radiotherapy is called myeloablative or high-dose therapy. This type of treatment is generally used before autologous transplantation in all patients and before allogeneic transplantation in younger patients.
An alternative way of preparing for an allogeneic transplant is to give lower doses of chemotherapy which is better tolerated by many patients. This type of treatment is called a reduced intensity or “mini” transplant. Although the pre-transplant treatment in this type of transplant is not designed to kill all of the patient’s tumour cells, long-term cure can be mediated by a graft-versus-leukaemia / lymphoma effect which is mediated by the new donor immune system which destroys any tumour cells that survive the chemotherapy.
There is another way of doing transplants which combines radiolabelled antibodies which seek out and destroy the tumour cells with a reduced intensity or “mini” transplant. This has the advantage of intensive tumour eradication with limited side-effects for the patient and is called targeted radiotherapy. This is currently being used for patients with multiple myeloma receiving an autologous transplant and for patients with acute leukaemia, myelodysplasia and multiple myeloma receiving an allogeneic transplant.
What are the common complications and how are they prevented and managed?
A number of complications might occur after an allogeneic transplant. The commonest are infections and graft-versus-host disease.
Bacterial of fungal Infections can occur early after transplant when the blood counts, particularly the neutrophils are low. These can be prevented and treated using antibiotics and antifungal drugs. In the first few months after transplant, patients may develop viral infections when natural immunity to infections is impaired. Cytomegalovirus or CMV is one of the commonest infections and can be treated with either antiviral drugs or by a transfusion of donor immune cells specifically selected to eradicate the virus.
Even in patients who are a full tissue match with their donor, there are genetic differences which cannot be tested for before the transplant. These differences can result in the donor immune cells or T cells attacking normal tissues in the patient – this process is called graft-versus-host disease (GVHD). The T cells are collected along with the stem cells and are the cause of GVHD.
GVHD can occur early after transplant(acute) or later after transplant (chronic). Symptoms of acute disease include skin rash and gastroenteritis or abdominal discomfort, which is caused by an inflammation of the liver and the lining of the intestine.
Your doctor may administer drugs which suppress the immune system such as methotrexate or cyclosporine to prevent GVHD from occurring. Drugs called corticosteroids may also be given to control the condition if and when it develops.
Prevention of GVHD using T cell Depletion
In T cell depleted transplants, the bone marrow or peripheral blood stem cells harvested from a donor can have the T cells removed to prevent GVHD. This can be done either by removing the T cells in the laboratory prior to infusion into the patient or by treating the patient with monoclonal antibodies which remove the T cells from the blood of the patient.
Because T cell-depleted transplants have a lower risk of GVHD, this approach can be used in transplants between patients and donors whose tissue types (HLA) are not fully matched. This type of transplant can be easier to tolerate, it may be available to older patients, even those over 60 years old provided they are otherwise medically fit.
Donor Lymphocyte Infusions (DLI)
For patients with certain types of cancer whose diseases recur late after transplantation, physicians may treat the patient with gradually increasing numbers of T cells from the original donor. The low levels of T cells can eliminate the recurrent cancer without causing significant graft-versus-host disease.DLI are often used in combination with reduced intensity or “mini” transplants to prevent relapse and increase the chances of long-term cure.
Please click here For Stem cell Registry ( Datri Blood Stem Cell Donors Registry www.datriworld.org )