Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood, in order to replicate inside a patient and produce additional normal blood cells. HSCT may be autologous (the patient's own stem cells are used), syngeneic (stem cells from an identical twin), or allogeneic (stem cells from a donor). It is most often performed for patients with certain cancers of the blood or bone marrow, such as multiple myeloma, leukemia, some types of lymphoma and immune deficiencies. In these cases, the recipient's immune system is usually suppressed with radiation or chemotherapy before the transplantation. Infection and graft-versus-host disease are major complications of allogeneic HSCT. HSCT remains a dangerous procedure with many possible complications; it is reserved for patients with life-threatening diseases. As survival following the procedure has increased, its use has expanded beyond cancer to autoimmune diseases and hereditary skeletal dysplasias, notably malignant infantile osteopetrosis and mucopolysaccharidosis.
Medical uses
Indications Indications for stem-cell transplantation are:
Malignant (cancerous) Acute myeloid leukemia Chronic myeloid leukemia Acute lymphoblastic leukemia Juvenile myelomonocytic leukemia Hodgkin lymphoma (relapsed, refractory) Non-Hodgkin lymphoma (relapsed, refractory) Neuroblastoma Ewing sarcoma Multiple myeloma Myelodysplastic syndromes Gliomas, other solid tumors
Nonmalignant (noncancerous) Thalassemia Sickle cell anemia Aplastic anemia Fanconi anemia Malignant infantile osteopetrosis Mucopolysaccharidosis Paroxysmal nocturnal hemoglobinuria Pyruvate kinase deficiency Immune deficiency syndromes Autoimmune diseases, including multiple sclerosis Many recipients of HSCTs are multiple myeloma or leukemia patients who would not benefit from prolonged treatment with, or are already resistant to, chemotherapy. Candidates for HSCTs include pediatric cases where the patient has an inborn defect such as severe combined immunodeficiency or congenital neutropenia with defective stem cells, and also children or adults with aplastic anemia who have lost their stem cells after birth. Other conditions treated with stem cell transplants include sickle cell disease, myelodysplastic syndrome, neuroblastoma, lymphoma, Ewing's sarcoma, desmoplastic small round cell tumor, chronic granulomatous disease, Hodgkin's disease and Wiskott–Aldrich syndrome. Non-myeloablative, so-called mini transplant (microtransplantation) procedures, have been developed requiring smaller doses of preparative chemotherapy and radiation therapy, allowing HSCT to be conducted in the elderly and other patients who would otherwise be considered too weak to withstand a conventional treatment regimen.
Number of procedures In 2006, 50,417 first HSCTs were recorded worldwide, according to a global survey of 1,327 centers in 71 countries conducted by the Worldwide Network for Blood and Marrow Transplantation. Of these, 28,901 (57%) were autologous and 21,516 (43%) were allogeneic (11,928 from family donors and 9,588 from unrelated donors). The main indications for transplant were lymphoproliferative disorders (55%) and leukemias (34%), and many took place in either Europe (48%) or the Americas (36%). The Worldwide Network for Blood and Marrow Transplantation reported the millionth transplant to have been undertaken in December 2012. In 2014, according to the World Marrow Donor Association, stem-cell products provided for unrelated transplantation worldwide had increased to 20,604 (4,149 bone-marrow donations, 12,506 peripheral blood stem-cell donations, and 3,949 cord-blood units).
Graft types
Autologous Autologous HSCT requires the extraction (apheresis) of hematopoietic stem cells (HSCs) from the patient and storage of the harvested cells in a freezer. The patient is then treated with high-dose chemotherapy with or without radiotherapy with the intention of eradicating the patient's malignant cell population at the cost of partial or complete bone marrow ablation (destruction of patient's bone marrow's ability to grow new blood cells). The patient's own stored stem cells are then transfused into their bloodstream, where they replace destroyed tissue and resume the patient's normal blood-cell production. Autologous transplants have the advantage of lower risk of infection during the immune-compromised portion of the treatment, since the recovery of immune function is rapid. Also, the incidence of patients experiencing rejection is very rare (and graft-versus-host disease impossible) due to the donor and recipient being the same individual. These advantages have established autologous HSCT as one of the standard second-line treatments for such diseases as lymphoma. For other cancers such as acute myeloid leukemia, though, the reduced mortality of the autogenous relative to allogeneic HSCT may be outweighed by an increased likelihood of cancer relapse and related mortality, so the allogeneic treatment may be preferred for those conditions. Autologous HSCT is also used as a treatment option for specific autoimmune conditions. It has been shown to be an effective treatment for multiple sclerosis in selected patients. It is used as a treatment option in cases where 'high-efficacy' treatments have failed, or in patients with aggressive, highly-active disease or other poor prognostic markers. The type of autologous HSCT used as a multiple sclerosis treatment is considered relatively safe and the serious adverse events rare. Researchers have conducted small studies using nonmyeloablative HSCT as a possible treatment for type 1 diabetes mellitus in children and adults. Results have been promising, but as of 2019, speculating whether these experiments will lead to effective treatments for diabetes is premature.
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