The number of circulating stem cells in the blood is low
compared with the number of stem cells in the bone marrow.
Mobilization is a technique that is used to increase the number
of circulating stem cells in the peripheral blood. Stem cell mobilization
is achieved using chemotherapy (chemomobilization),
growth factors (G-mobilization), or both. Chemotherapy followed
by use of a growth factor could increase the number of
circulating progenitor cells by approximately 60-fold, whereas
use of a growth factor alone can result in an 18-fold increase in
circulating stem cells. Chemomobilization with growth factor
mobilization is the most common method of stem cell collection;
the synergistic technique reduces the number of apheresis needed
to collect adequate cells for hematopoietic reconstitution. In
some patients, however, growth factor mobilization is preferred
when chemotherapy for further reduction of myeloma burden
is not a critical need prior to stem cell collection (i.e., patient’s
myeloma burden is signifi cantly reduced by primary induction
chemotherapy). Growth factor mobilization alone can yield an
adequate number of stem cells required for transplantation.
Optimal mobilization techniques have not yet been determined,
but combination agents of chemotherapy and colony-stimulating
factors are believed to give optimal cell yield. The two most common
agents for stem cell mobilization are cyclophosphamide 2–4
g/m2 and granulocyte macrophage–colony-stimulating factors or
granulocyte colony-stimulating factors