Type of Transplant
There are three main types of transplants:
- HSCs come from someone other than the recipient. These can be from someone related (e.g. sibling most commonly; rarely a parent) or someone unrelated (through international BMT registries).
- Most transplants are allogeneic and they carry the highest risk of complications.
- As the donor HSCs are genetically different from the recipient they recognize host cells as foreign. This leads to the potential for the most feared complication of HSCT, graft-versus-host disease (GVHD).
- Genetic disparity is also used therapeutically, particularly in high-risk or relapsed leukemias that are resistant to further chemotherapy, due to a graft-versus-leukemia (GVL) effect. GVL is why most leukemia is ultimately cured by HSCT.
- HSCs come from the recipient themselves.
- Autologous transplants are typically performed as a “stem cell rescue” to allow otherwise supralethal doses of myeloablative chemotherapy / radiation therapy to be administered.
- Usually this is in the setting of solid tumors such as neuroblastoma and infant brain tumors, however, in adult oncology autologous transplants may be performed for acute leukemias and multiple myeloma.
- HSCs come from an identical twin.
- These are rarely performed because of lack of ability.
- Syngeneic transplants are excellent for non-malignant disorders as there is no deleterious GVHD reaction (and a GVL effect is not needed).