Blood, 1 September 2002, Vol. 100, No. 5, pp. 1523-1523
Blood or marrow stem cells?
In the beginning, there was bone marrow. A quarter of a century
ago, the concept was simple: a patient had a bad bone marrow (eg,
aplastic anemia) or a marrow destroyed by therapy (acute leukemia), and
one substituted a healthy, allogeneic marrow. Gradually it became
possible to distinguish and then manipulate marrow cellular subsets.
For instance, T lymphocytes were found to be important in acute
graft-versus-host disease (AGVHD), and strategies evolved to
reduce their numbers in the marrow inoculum. The results were mixed, with graft failure and increased relapse replacing the problem
of AGVHD. Once the hematopoietic progenitor cells were recognizable, it was seen that placental blood had large
numbers of such and also that the T-lymphocyte population
appeared naive: perhaps one could get engraftment with less AGVHD.
Again, the results were mixed: less AGVHD, but slower engraftment. More
recently, allogeneic cytokine-mobilized peripheral blood stem cells
(PBSCs) have come under study. On the one hand, large numbers of
CD34+ cells can be collected, but there were concerns about
an increased risk of chronic graft-versus-host disease (CGHVD). PBSC
products contain large numbers of T lymphocytes, and previous
experience using noncytokine mobilized peripheral blood cells clearly
showed a higher risk of CGVHD (although with more reliable engraftment in aplastic anemia patients).
The study in this issue (page 1525) reports a multicenter, randomized
trial comparing marrow to cytokine-moblized PBSCs. The results are
similar to those previously published by the Seattle group: the PBSC
group had faster engraftment (4 days for neutrophils, 6 days for
platelets) and slightly better survival. The current study shows that
most of the survival advantage is seen in the poor-risk patients, as
opposed to the good-risk ones: this again is similar to what Seattle
showed. The reason for the advantage in the poor-risk patients is not
clear: 4 days faster engraftment would seem to be advantageous,
but it might be useful to also study whether there are relevant
differences in the cellular components in the respective products which
could explain such an advantage, such as larger numbers of cells to
suppress incipient infections or to speed healing of previous
endothelial damage.
Patrick G. Beatty
Montana Cancer
Specialists
