A bone marrow transplant is a procedure to replace damaged or destroyed bone marrow with healthy bone marrow stem cells. Bone marrow is the soft, fatty tissue inside your bones. The bone marrow produces blood cells. Stem cells are immature cells in the bone marrow that give rise to all of your different blood cells.
Before the transplant, chemotherapy, radiation, or both may be given. This may be done in two ways:
Ablative (myeloablative) treatment -- High-dose chemotherapy, radiation, or both are given to kill any cancer cells. This also kills all healthy bone marrow that remains, and allows new stem cells to grow in the bone marrow.
Reduced-intensity treatment also called a mini transplant -- Lower doses of chemotherapy and radiation are given before a transplant. This allows older people, and those with other health problems to have a transplant.