A comprehensive review of bone marrow transplantation

Autologous bone marrow transplantation involves transplanting autologous stem cells that are taken from the patient and are pre-frozen and then transplanted back into the patient after the completion of chemotherapy with large doses. Unlike allogeneic transplantation, in which the cells prepared for transplantation are taken from a donor when performing autologous cell transplantation, the patient’s or donor’s immune system does not have any role that may affect the transplantation process.

The premise underlying the transplant is based on that if we double the dose of chemotherapy that we give to a patient with a cancerous tumor responding to treatment by 5-10 times, we succeed in eliminating a greater number of cancer cells, which makes more patients enjoy periods of absence When symptoms are almost gone, this period is called remission, and it increases the likelihood of more patients of recovery. So, autotransplantation is a way to enable a patient to receive high doses of chemotherapy, even if to an extent that damages the patient’s healthy stem cells. However, the damage caused by chemotherapy to stem cells can be bypassed by re-implanting the patient’s own stem cells.

Autotransplantation has several advantages when compared to allogeneic implants:

  • In this way, each patient has a self-donor, unlike an allogeneic transplant, in which only 20% to 30% of patients have a suitable donor from the same family.
  • The risks are lower with autotransplantation.
  • There is no risk of the body rejecting the transplant.
  • There is no risk of the patient developing graft versus host disease, which is the most serious disadvantage of allogeneic transplantation.
  • The symmetry of the nerve system for healing after the autotransplantation is faster than in the allogeneic transplant, so the incidence of infectious diseases, especially viral infections such as cytomegalovirus infection, is lower.
  • Given that there is a lower risk when performing autotransplantation, the morbidity, and death rates after transplantation is less than 5%, it is possible to perform the self-transplant without specifying the patient’s age.
    Autologous transplantation is the most popular one, because of its advantages compared to allogeneic transplantation, for example, a total of 24,154 transplants were performed in Europe during 2002, of which 16,136 were autotransplantations while only 8,018 of them were allogeneic transplants.

Autotransplantation is performed on patients with diseases:

  • Non-Hodgkin lymphoma, Myeloma, Hodgkin lymphoma, and in solid tumors (although there is a significant decrease in the percentage of autotransplantation in solid tumors, especially in cancerous breast tumors). In patients suffering from acute and chronic leukemia (Acute / Chronic Leukemia), allogeneic transplantation is performed more than autotransplantation, especially in patients who are still in the first remission stage of the disease.
    The source of the autograft may be bone marrow, peripheral blood, and in rare cases, the graft may be taken from Umbilical cord blood. The first transplants were performed on stem cells from the bone marrow. However, the acceptance of these cells by the body was slow. When Hematopoietic Growth Factors such as G-CSF are used, there is a certain improvement in the acceptability of the transplant by the patient (stem cell infusion).
  • In auto culture, 108×5-3 mononuclear cells per kilogram or 106×5-3 stem cells per kilogram infusion. There is usually a relationship between the number of stem cells that are infused and the speed at which the patient accepts them, but this relationship is not inevitable. In some cases, the body may accept the cells when a much smaller number of stem cells are leaked.
  • The types of chemotherapy that are used vary with the type of tumor. Treatment may or may not involve comprehensive radiotherapy. The treatment is usually a combination of different types of chemotherapy treatments with a synergistic effect.
    BEAM is the most widely used chemotherapy in autotransplantation in lymphoma cases, which consists of the drugs Melphalan, Arabinofuranosyl cytidine-ARA-C, Etoposide, and BNCU. Myeloma treatment is based on the use of Melphalan.

However, there are some drawbacks to autotransplantation compared to allogeneic transplantation (when the source of the transplanted cells is from a donor), the most important of which are:

1 Contamination of the graft with cancer cells. This infection is especially common in various cases of leukemia, but it also occurs in lymphomas and solid tumors. In these cases, it is possible to perform graft purification from the tumor cells (purging) by using monoclonal antibodies.
An example of this is the use of anti-B or T cells in cases of treatment of lymphoma, or treatment with cytotoxic substances, especially derivatives of cyclophosphamide (HC-4), and more recently by isolating CD34 + stem cells from the graft and culturing isolated and purified stem cells for the patient. It is also possible to combine the two methods, ie, isolating CD34 + in the first stage, and then performing graft purification from tumor cells using specific antibodies against tumor cells.

2 As for the second disadvantage of auto-transplantation compared to allogeneic transplantation, it is the lack of a graft-versus-tumor GVT reaction, and this reaction is by attacking the immune system cells present in the graft, especially cytotoxic T cells and cells. Natural Killer Cells of Minimal Residual Disease-MRD that was left after completion of chemotherapy given in large doses as preparation for transplantation.
The attempts today focus on overcoming this deficiency, by administering the patient to cytokines of the type Interleukin-2 or interferon, or by giving the patient monoclonal antibodies of the anti-CD20 type (in cases Treating lymphoma), or giving the patient lymphocytes and other cells of the immune system that are engineered to become anti-tumor after autotransplantation. Specialists in modern methods of treatment try to find ways to stimulate an immune attack against tumor cells after the completion of the autotransplantation process, similar to the reaction of the graft against the tumor that occurs when performing an allogeneic transplant.

Spread the love

Leave a Reply

Your email address will not be published. Required fields are marked *

GIPHY App Key not set. Please check settings