Hematopoietic stem cell transplantation (HSCT) is a medical procedure in which blood-forming stem cells are infused into a patient to restore or replace blood-cell production. The cells may come from the patient or another person and are obtained from bone marrow, circulating blood, or umbilical cord blood. HSCT is used for selected blood cancers and nonmalignant blood disorders. Bone marrow transplantation is specifically the form that uses marrow-derived cells, although the term is sometimes used more broadly. (nhlbi.nih.gov)
Biological basis and therapeutic roles
Hematopoietic stem cells generate the principal blood-cell lineages, including red blood cells, white blood cells, and platelets. After intravenous infusion, transplanted cells travel to the marrow and can establish new blood-cell production. This is not a surgical implantation of marrow into bones. (cancer.gov)
HSCT has two major therapeutic roles. It can provide hematopoietic recovery after intensive chemotherapy, sometimes combined with radiation therapy, that damages the patient’s blood-forming cells. In transplantation from a donor, it can also provide an immunological attack on residual cancer cells. This graft-versus-leukemia effect, also called graft-versus-tumor activity, involves donor immune cells, including T cells, recognizing and attacking malignant cells. It is distinct from the direct anticancer action of the conditioning treatment. (cancer.gov)
Types of transplantation
Autologous transplantation uses the patient’s own cells, collected before high-dose treatment and stored until infusion. Its principal purpose in cancer treatment is to restore blood-cell production after intensive therapy. There is a small risk that malignant cells may be present in the collected product. Allogeneic transplantation uses cells from another person, who may be a relative or an unrelated donor. Syngeneic transplantation, a less common category, uses cells from an identical twin. (cancer.gov)
The relationship between donor and recipient is separate from the source of the cells: a peripheral-blood or marrow graft can be either autologous or allogeneic. Umbilical cord blood provides another source of donated blood-forming cells. (cancer.gov)
Clinical applications
HSCT is most commonly used for selected patients with leukemia, lymphoma, multiple myeloma, or myelodysplastic syndromes. The indication depends on the particular disease, its stage and response to treatment, previous therapies, donor availability, and the patient’s ability to tolerate the procedure. A diagnosis alone does not establish that transplantation is appropriate. (cancer.gov)
Nonmalignant applications include severe aplastic anemia and certain inherited blood disorders, including sickle cell disease and thalassemia. In these settings, transplantation aims to establish functioning donor-derived blood production rather than eliminate a cancer. (nhlbi.nih.gov)
Cell collection and donor matching
Peripheral-blood collection generally follows medication that increases the number of circulating stem cells. Blood passes through an apheresis machine, which collects the required cells and returns the remaining blood components. Marrow cells are collected through needles placed in the pelvic bones under anesthesia. Cord blood is collected from the umbilical cord and placenta after birth, then processed and frozen. These are collection procedures; the recipient receives the resulting product by infusion. (cancer.gov)
Allogeneic donor selection includes tissue typing for human leukocyte antigens, or HLA, the human major histocompatibility complex. Close HLA compatibility helps reduce complications. Donor searches may examine relatives, unrelated donor registries, and stored cord-blood units. A haploidentical transplant uses a partially matched relative, often a parent, child, or sibling. Cord-blood transplantation can accommodate less stringent matching than some adult-donor approaches. (nmdp.org)
Conditioning, infusion, and engraftment
Before infusion, patients receive a conditioning regimen. Depending on the disease and transplant type, its objectives include treating malignancy and suppressing the recipient’s immune system sufficiently to permit donor-cell establishment. Regimens may include chemotherapy, immunotherapy, and radiation. Myeloablative regimens profoundly damage existing hematopoiesis; reduced-intensity and nonmyeloablative approaches use different degrees of suppression and, in malignant disease, depend more heavily on donor immune activity. (cancer.gov)
Engraftment occurs when the infused cells begin producing blood cells. Blood counts are monitored to assess this process. Engraftment is an important recovery milestone, but it does not mean that immune function has fully recovered or that the underlying disease has been cured. Immune recovery and other aspects of physical recovery continue after initial blood-count improvement. (nmdp.org)
Complications and follow-up
Early complications include infection, bleeding, nausea, fatigue, mouth sores, and treatment-related organ injury. Donor cells may fail to establish adequate hematopoiesis, and immune rejection is another possible complication of allogeneic transplantation. These risks arise from both the preparative treatment and interactions between donor and recipient. (nhlbi.nih.gov)
Graft-versus-host disease occurs when donor immune cells attack recipient tissues. It can affect the skin, liver, intestines, and other organs. Unlike graft rejection, in which the recipient attacks the graft, it represents immune activity in the opposite direction. (cancer.gov)
Long-term effects can include infertility, cataracts, secondary cancers, and persistent organ damage. Follow-up therefore extends beyond engraftment and includes assessment of disease status, blood production, immune recovery, and late complications. The duration and course of recovery vary substantially with the disease, graft, conditioning regimen, and complications experienced. (cancer.gov)