Hematopoietic stem cell transplantation (HSCT)

Hematopoietic stem cell transplantation (HSCT), also known as bone marrow transplantation, is a form of therapy that involves taking stem cells from a donor or from cord blood and infusing them intravenously to the recipient. Sources of these stem cells can be:

• from the patient (autologous)
• from a relative (allogeneic)
• from a matched unrelated donor (MUD)
• from a banked unrelated cord blood unit appropriately matched to the patient

Rationale for use of HSCT

Many chemotherapeutic agents and radiation damage the bone marrow beyond normal recovery. The use of HSCT allows use of higher dose of drugs and radiation to treat the primary condition. The indications for HSCT include pediatric malignancies/cancers and non-malignant disorders (i.e. bone marrow failure conditions and a variety of other disorders)

Types of HSCT

Allogeneic

• Syngeneic, i.e. from an identical twin
• Matched related: usually from an HLA matched sibling
• Matched unrelated (MUD): the donor is usually identified through a donor registry, used if there is no matched related donor available
• Partially matched related donor: may be used if there is no matched donor available.
• Cord blood: The stem cells from cord blood can be used for a matched or partially matched allogeneic HSCT

Autologous

• Autologous purged transplant (i.e. treated ex vivo to remove malignant cells)
• Autologous non-purged: used for diseases that do not infiltrate the bone marrow to allow ultra high doses of chemotherapy and radiotherapy, e.g. Hodgkin's Lymphoma.

Common complications of HSCT

1. Toxicity from the chemotherapy and/or radiotherapy, e.g. GI inflammation, liver, renal and lung toxicity.
2. Complications of pancytopenia - bleeding, infection, and anemia.
3. Immunological problems:
• Graft versus host disease: the bone marrow graft recognizes the host as being foreign and attacks the host cells. This results in an autoimmune disease primarily affecting the skin, liver, GI tract and joints
• Rejection of the graft
• Immunodeficiency
4. Long-term toxicity: includes endocrine and growth abnormalities, cataracts, decreased fertility, learning disabilities and second malignancy.